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+title: "Abyssal plain"
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+source: "https://en.wikipedia.org/wiki/Abyssal_plain"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:14.960702+00:00"
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+---
+
+An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft). Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins, the other elements being an elevated mid-ocean ridge and flanking abyssal hills.
+The creation of the abyssal plain is the result of the spreading of the seafloor (plate tectonics) and the melting of the lower oceanic crust. Magma rises from above the asthenosphere (a layer of the upper mantle), and as this basaltic material reaches the surface at mid-ocean ridges, it forms new oceanic crust, which is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited by turbidity currents that have been channelled from the continental margins along submarine canyons into deeper water. The rest is composed chiefly of pelagic sediments. Metallic nodules are common in some areas of the plains, with varying concentrations of metals, including manganese, iron, nickel, cobalt, and copper. There are also amounts of carbon, nitrogen, phosphorus and silicon, due to material that comes down and decomposes.
+Owing in part to their vast size, abyssal plains are believed to be major reservoirs of biodiversity. They also exert significant influence upon ocean carbon cycling, dissolution of calcium carbonate, and atmospheric CO2 concentrations over time scales of a hundred to a thousand years. The structure of abyssal ecosystems is strongly influenced by the rate of flux of food to the seafloor and the composition of the material that settles. Factors such as climate change, fishing practices, and ocean fertilization have a substantial effect on patterns of primary production in the euphotic zone. Animals absorb dissolved oxygen from the oxygen-poor waters. Much dissolved oxygen in abyssal plains came from polar regions that had melted long ago. Due to scarcity of oxygen, abyssal plains are inhospitable for organisms that would flourish in the oxygen-enriched waters above. Deep sea coral reefs are mainly found in depths of 3,000 meters and deeper in the abyssal and hadal zones.
+Abyssal plains were not recognized as distinct physiographic features of the sea floor until the late 1940s and, until recently, none had been studied on a systematic basis. They are poorly preserved in the sedimentary record, because they tend to be consumed by the subduction process. Due to darkness and a water pressure that can reach about 750 times atmospheric pressure (76 megapascal), abyssal plains are not well explored.
+
+== Oceanic zones ==

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+title: "Abyssal plain"
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+source: "https://en.wikipedia.org/wiki/Abyssal_plain"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:14.960702+00:00"
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+---
+
+The ocean can be conceptualized as zones, depending on depth, and presence or absence of sunlight. Nearly all life forms in the ocean depend on the photosynthetic activities of phytoplankton and other marine plants to convert carbon dioxide into organic carbon, which is the basic building block of organic matter. Photosynthesis in turn requires energy from sunlight to drive the chemical reactions that produce organic carbon.
+The stratum of the water column nearest the surface of the ocean (sea level) is referred to as the photic zone. The photic zone can be subdivided into two different vertical regions. The uppermost portion of the photic zone, where there is adequate light to support photosynthesis by phytoplankton and plants, is referred to as the euphotic zone (also referred to as the epipelagic zone, or surface zone). The lower portion of the photic zone, where the light intensity is insufficient for photosynthesis, is called the dysphotic zone (dysphotic means "poorly lit" in Greek). The dysphotic zone is also referred to as the mesopelagic zone, or the twilight zone. Its lowermost boundary is at a thermocline of 12 °C (54 °F), which, in the tropics generally lies between 200 and 1,000 metres (660 and 3,280 ft).
+The euphotic zone is somewhat arbitrarily defined as extending from the surface to the depth where the light intensity is approximately 0.1–1% of surface sunlight irradiance, depending on season, latitude and degree of water turbidity. In the clearest ocean water, the euphotic zone may extend to a depth of about 150 m, or rarely, up to 200 m. Dissolved substances and solid particles absorb and scatter light, and in coastal regions the high concentration of these substances causes light to be attenuated rapidly with depth. In such areas the euphotic zone may be only a few tens of metres deep or less. The dysphotic zone, where light intensity is considerably less than 1% of surface irradiance, extends from the base of the euphotic zone to about 1,000 m. Extending from the bottom of the photic zone down to the seabed is the aphotic zone, a region of perpetual darkness.
+Since the average depth of the ocean is about 4,300 m (14,100 ft), the photic zone represents only a tiny fraction of the ocean's total volume. However, due to its capacity for photosynthesis, the photic zone has the greatest biodiversity and biomass of all oceanic zones. Nearly all primary production in the ocean occurs here. Life forms which inhabit the aphotic zone are often capable of movement upwards through the water column into the photic zone for feeding. Otherwise, they must rely on material sinking from above, or find another source of energy and nutrition, such as occurs in chemosynthetic archaea found near hydrothermal vents and cold seeps.
+The aphotic zone can be subdivided into three different vertical regions, based on depth and temperature. First is the bathyal zone, extending from a depth of 1,000 to 3,000 m (3,300 to 9,800 ft), with water temperature decreasing from 12 °C (54 °F) to 4 °C (39 °F) as depth increases. Next is the abyssal zone, extending from a depth of 3,000 to 6,000 m (9,800 to 19,700 ft). The final zone includes the deep oceanic trenches, and is known as the hadal zone. This, the deepest oceanic zone, extends from a depth of 6,000 m to approximately 11,034 m (36,201 ft), at the very bottom of the Mariana Trench, the deepest point on Earth. Abyssal plains are typically in the abyssal zone, at depths from 3,000 to 6,000 m.
+The table below illustrates the classification of oceanic zones:
+
+== Formation ==

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+title: "Abyssal plain"
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+category: "reference"
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+---
+
+Oceanic crust, which forms the bedrock of abyssal plains, is continuously being created at mid-ocean ridges (a type of divergent boundary) by a process known as decompression melting. Plume-related decompression melting of solid mantle is responsible for creating ocean islands like the Hawaiian islands, as well as the ocean crust at mid-ocean ridges. This phenomenon is also the most common explanation for flood basalts and oceanic plateaus (two types of large igneous provinces). Decompression melting occurs when the upper mantle is partially melted into magma as it moves upwards under mid-ocean ridges. This upwelling magma then cools and solidifies by conduction and convection of heat to form new oceanic crust. Accretion occurs as mantle is added to the growing edges of a tectonic plate, usually associated with seafloor spreading. The age of oceanic crust is therefore a function of distance from the mid-ocean ridge. The youngest oceanic crust is at the mid-ocean ridges, and it becomes progressively older, cooler and denser as it migrates outwards from the mid-ocean ridges as part of the process called mantle convection.
+The lithosphere, which rides atop the asthenosphere, is divided into a number of tectonic plates that are continuously being created and consumed at their opposite plate boundaries. Oceanic crust and tectonic plates are formed and move apart at mid-ocean ridges. Abyssal hills are formed by stretching of the oceanic lithosphere. Consumption or destruction of the oceanic lithosphere occurs at oceanic trenches (a type of convergent boundary, also known as a destructive plate boundary) by a process known as subduction. Oceanic trenches are found at places where the oceanic lithospheric slabs of two different plates meet, and the denser (older) slab begins to descend back into the mantle. At the consumption edge of the plate (the oceanic trench), the oceanic lithosphere has thermally contracted to become quite dense, and it sinks under its own weight in the process of subduction. The subduction process consumes older oceanic lithosphere, so oceanic crust is seldom more than 200 million years old. The overall process of repeated cycles of creation and destruction of oceanic crust is known as the Supercontinent cycle, first proposed by Canadian geophysicist and geologist John Tuzo Wilson.
+New oceanic crust, closest to the mid-oceanic ridges, is mostly basalt at shallow levels and has a rugged topography. The roughness of this topography is a function of the rate at which the mid-ocean ridge is spreading (the spreading rate). Magnitudes of spreading rates vary quite significantly. Typical values for fast-spreading ridges are greater than 100 mm/yr, while slow-spreading ridges are typically less than 20 mm/yr. Studies have shown that the slower the spreading rate, the rougher the new oceanic crust will be, and vice versa. It is thought this phenomenon is due to faulting at the mid-ocean ridge when the new oceanic crust was formed. These faults pervading the oceanic crust, along with their bounding abyssal hills, are the most common tectonic and topographic features on the surface of the Earth. The process of seafloor spreading helps to explain the concept of continental drift in the theory of plate tectonics.
+The flat appearance of mature abyssal plains results from the blanketing of this originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited from turbidity currents that have been channeled from the continental margins along submarine canyons down into deeper water. The remainder of the sediment comprises chiefly dust (clay particles) blown out to sea from land, and the remains of small marine plants and animals which sink from the upper layer of the ocean, known as pelagic sediments. The total sediment deposition rate in remote areas is estimated at two to three centimeters per thousand years. Sediment-covered abyssal plains are less common in the Pacific Ocean than in other major ocean basins because sediments from turbidity currents are trapped in oceanic trenches that border the Pacific.
+Abyssal plains are typically covered by deep sea, but during parts of the Messinian salinity crisis much of the Mediterranean Sea's abyssal plain was exposed to air as an empty deep hot dry salt-floored sink.
+
+== Discovery ==
+
+The landmark scientific expedition (December 1872 – May 1876) of the British Royal Navy survey ship HMS Challenger yielded a tremendous amount of bathymetric data, much of which has been confirmed by subsequent researchers. Bathymetric data obtained during the course of the Challenger expedition enabled scientists to draw maps, which provided a rough outline of certain major submarine terrain features, such as the edge of the continental shelves and the Mid-Atlantic Ridge. This discontinuous set of data points was obtained by the simple technique of taking soundings by lowering long lines from the ship to the seabed.
+The Challenger expedition was followed by the 1879–1881 expedition of the Jeannette, led by United States Navy Lieutenant George Washington DeLong. The team sailed across the Chukchi Sea and recorded meteorological and astronomical data in addition to taking soundings of the seabed. The ship became trapped in the ice pack near Wrangel Island in September 1879, and was ultimately crushed and sunk in June 1881.
+The Jeannette expedition was followed by the 1893–1896 Arctic expedition of Norwegian explorer Fridtjof Nansen aboard the Fram, which proved that the Arctic Ocean was a deep oceanic basin, uninterrupted by any significant land masses north of the Eurasian continent.

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+
+Beginning in 1916, Canadian physicist Robert William Boyle and other scientists of the Anti-Submarine Detection Investigation Committee (ASDIC) undertook research which ultimately led to the development of sonar technology. Acoustic sounding equipment was developed which could be operated much more rapidly than the sounding lines, thus enabling the German Meteor expedition aboard the German research vessel Meteor (1925–27) to take frequent soundings on east-west Atlantic transects. Maps produced from these techniques show the major Atlantic basins, but the depth precision of these early instruments was not sufficient to reveal the flat featureless abyssal plains.
+As technology improved, measurement of depth, latitude and longitude became more precise and it became possible to collect more or less continuous sets of data points. This allowed researchers to draw accurate and detailed maps of large areas of the ocean floor. Use of a continuously recording fathometer enabled Tolstoy & Ewing in the summer of 1947 to identify and describe the first abyssal plain. This plain, south of Newfoundland, is now known as the Sohm Abyssal Plain. Following this discovery many other examples were found in all the oceans.
+The Challenger Deep is the deepest surveyed point of all of Earth's oceans; it is at the south end of the Mariana Trench near the Mariana Islands group. The depression is named after HMS Challenger, whose researchers made the first recordings of its depth on 23 March 1875 at station 225. The reported depth was 4,475 fathoms (8184 m) based on two separate soundings. On 1 June 2009, sonar mapping of the Challenger Deep by the Simrad EM120 multibeam sonar bathymetry system aboard the R/V Kilo Moana indicated a maximum depth of 10,971 m (6.82 miles). The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth (an error of about 22 m at this depth).
+
+== Terrain features ==
+
+=== Hydrothermal vents ===
+
+A rare but important terrain feature found in the bathyal, abyssal and hadal zones is the hydrothermal vent. In contrast to the approximately 2 °C ambient water temperature at these depths, water emerges from these vents at temperatures ranging from 60 °C up to as high as 464 °C. Due to the high barometric pressure at these depths, water may exist in either its liquid form or as a supercritical fluid at such temperatures.
+At a barometric pressure of 218 atmospheres, the critical point of water is 375 °C. At a depth of 3,000 m, the barometric pressure of sea water is more than 300 atmospheres (as salt water is denser than fresh water). At this depth and pressure, seawater becomes supercritical at a temperature of 407 °C (see image). However the increase in salinity at this depth pushes the water closer to its critical point. Thus, water emerging from the hottest parts of some hydrothermal vents, black smokers and submarine volcanoes can be a supercritical fluid, possessing physical properties between those of a gas and those of a liquid.
+Sister Peak (Comfortless Cove Hydrothermal Field, 4°48′S 12°22′W, elevation −2,996 m), Shrimp Farm and Mephisto (Red Lion Hydrothermal Field, 4°48′S 12°23′W, elevation −3,047 m), are three hydrothermal vents of the black smoker category, on the Mid-Atlantic Ridge near Ascension Island. They are presumed to have been active since an earthquake shook the region in 2002. These vents have been observed to vent phase-separated, vapor-type fluids. In 2008, sustained exit temperatures of up to 407 °C were recorded at one of these vents, with a peak recorded temperature of up to 464 °C. These thermodynamic conditions exceed the critical point of seawater, and are the highest temperatures recorded to date from the seafloor. This is the first reported evidence for direct magmatic-hydrothermal interaction on a slow-spreading mid-ocean ridge. The initial stages of a vent chimney begin with the deposition of the mineral anhydrite. Sulfides of copper, iron, and zinc then precipitate in the chimney gaps, making it less porous over the course of time. Vent growths on the order of 30 cm (1 ft) per day have been recorded. An April 2007 exploration of the deep-sea vents off the coast of Fiji found those vents to be a significant source of dissolved iron (see iron cycle).
+Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust is being formed.
+
+=== Cold seeps ===
+
+Another unusual feature found in the abyssal and hadal zones is the cold seep, sometimes called a cold vent. This is an area of the seabed where seepage of hydrogen sulfide, methane and other hydrocarbon-rich fluid occurs, often in the form of a deep-sea brine pool. The first cold seeps were discovered in 1983, at a depth of 3,200 m in the Gulf of Mexico. Since then, cold seeps have been discovered in many other areas of the World Ocean, including the Monterey Submarine Canyon just off Monterey Bay, California, the Sea of Japan, off the Pacific coast of Costa Rica, off the Atlantic coast of Africa, off the coast of Alaska, and under an ice shelf in Antarctica.
+
+== Biodiversity ==

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+title: "Abyssal plain"
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+
+Fueled by the chemicals dissolved in the vent fluids, these areas are often home to large and diverse communities of thermophilic, halophilic and other extremophilic prokaryotic microorganisms (such as those of the sulfide-oxidizing genus Beggiatoa), often arranged in large bacterial mats near cold seeps. In these locations, chemosynthetic archaea and bacteria typically form the base of the food chain. Although the process of chemosynthesis is entirely microbial, these chemosynthetic microorganisms often support vast ecosystems consisting of complex multicellular organisms through symbiosis. These communities are characterized by species such as vesicomyid clams, mytilid mussels, limpets, isopods, giant tube worms, soft corals, eelpouts, galatheid crabs, and alvinocarid shrimp. The deepest seep community discovered thus far is in the Japan Trench, at a depth of 7700 meters. Probably the most important ecological characteristic of abyssal ecosystems is energy limitation. Abyssal seafloor communities are considered to be food limited because benthic production depends on the input of detrital organic material produced in the euphotic zone, thousands of meters above. Most of the organic flux arrives as an attenuated rain of small particles (typically, only 0.5–2% of net primary production in the euphotic zone), which decreases inversely with water depth. The small particle flux can be augmented by the fall of larger carcasses and downslope transport of organic material near continental margins.

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+
+== Exploitation of resources ==
+
+In addition to their high biodiversity, abyssal plains are of great current and future commercial and strategic interest. For example, they may be used for the legal and illegal disposal of large structures such as ships and oil rigs, radioactive waste and other hazardous waste, such as munitions. They may also be attractive sites for deep-sea fishing, and extraction of oil and gas and other minerals. Future deep-sea waste disposal activities that could be significant by 2025 include emplacement of sewage and sludge, carbon sequestration, and disposal of dredge spoils.
+As fish stocks dwindle in the upper ocean, deep-sea fisheries are increasingly being targeted for exploitation. Because deep sea fish are long-lived and slow growing, these deep-sea fisheries are not thought to be sustainable in the long term given current management practices. Changes in primary production in the photic zone are expected to alter the standing stocks in the food-limited aphotic zone.
+Hydrocarbon exploration in deep water occasionally results in significant environmental degradation resulting mainly from accumulation of contaminated drill cuttings, but also from oil spills. While the oil blowout involved in the Deepwater Horizon oil spill in the Gulf of Mexico originates from a wellhead only 1,500 m below the ocean surface, it nevertheless illustrates the kind of environmental disaster that can result from mishaps related to offshore drilling for oil and gas.
+Sediments of certain abyssal plains contain abundant mineral resources, notably polymetallic nodules. These potato-sized concretions of manganese, iron, nickel, cobalt, and copper, distributed on the seafloor at depths of greater than 4,000 m, are of significant commercial interest. The area of maximum commercial interest for polymetallic nodule mining (called the Pacific nodule province) lies in international waters of the Pacific Ocean, stretching from 118°–157°, and from 9°–16°N, an area of more than 3 million km2. The abyssal Clarion-Clipperton fracture zone (CCFZ) is an area within the Pacific nodule province that is currently under exploration for its mineral potential.
+Eight commercial contractors are currently licensed by the International Seabed Authority (an intergovernmental organization established to organize and control all mineral-related activities in the international seabed area beyond the limits of national jurisdiction) to explore nodule resources and to test mining techniques in eight claim areas, each covering 150,000 km2. When mining ultimately begins, each mining operation is projected to directly disrupt 300–800 km2 of seafloor per year and disturb the benthic fauna over an area 5–10 times that size due to redeposition of suspended sediments. Thus, over the 15-year projected duration of a single mining operation, nodule mining might severely damage abyssal seafloor communities over areas of 20,000 to 45,000 km2 (a zone at least the size of Massachusetts).
+Limited knowledge of the taxonomy, biogeography and natural history of deep sea communities prevents accurate assessment of the risk of species extinctions from large-scale mining. Data acquired from the abyssal North Pacific and North Atlantic suggest that deep-sea ecosystems may be adversely affected by mining operations on decadal time scales. In 1978, a dredge aboard the Hughes Glomar Explorer, operated by the American mining consortium Ocean Minerals Company (OMCO), made a mining track at a depth of 5,000 m in the nodule fields of the CCFZ. In 2004, the French Research Institute for Exploitation of the Sea (IFREMER) conducted the Nodinaut expedition to this mining track (which is still visible on the seabed) to study the long-term effects of this physical disturbance on the sediment and its benthic fauna. Samples taken of the superficial sediment revealed that its physical and chemical properties had not shown any recovery since the disturbance made 26 years earlier. On the other hand, the biological activity measured in the track by instruments aboard the crewed submersible bathyscaphe Nautile did not differ from a nearby unperturbed site. This data suggests that the benthic fauna and nutrient fluxes at the water–sediment interface has fully recovered.
+
+== List of abyssal plains ==
+
+== See also ==
+
+List of oceanic landforms
+List of submarine topographical features
+Oceanic ridge
+Physical oceanography
+
+== References ==
+
+== Bibliography ==
+
+== External links ==
+Monterey Bay Aquarium Research Institute (3 November 2009). "Deep-sea Ecosystems Affected By Climate Change". ScienceDaily. Retrieved 18 June 2010.

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+
+The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. The word abyss comes from the Greek word ἄβυσσος (ábussos), meaning "bottomless". At depths of 4,000–6,000 m (13,000–20,000 ft), this zone remains in perpetual darkness. It covers 83% of the total area of the ocean and 60% of Earth's surface. The abyssal zone has temperatures around 2–3 °C (36–37 °F) through the large majority of its mass. The water pressure can reach up to 76 MPa (750 atm; 11,000 psi).
+As there is no light, photosynthesis cannot occur, and there are no plants producing molecular oxygen (O2), which instead primarily comes from ice that had melted long ago from the polar regions. The water along the seafloor of this zone is largely devoid of molecular oxygen, resulting in a death trap for organisms unable to quickly return to the oxygen-enriched water above or to survive in the low-oxygen environment. This region also contains a much higher concentration of nutrient salts, like nitrogen, phosphorus, and silica, due to the large amount of dead organic material that drifts down from the ocean zones above and decomposes.
+The region below the abyssal zone is the sparsely inhabited hadal zone. The region above is the bathyal zone.
+
+== Trenches ==
+
+The deep trenches or fissures that plunge down thousands of meters below the ocean floor (for example, the mid-oceanic trenches such as the Mariana Trench in the Pacific) are almost unexplored. Previously, only the bathyscaphe Trieste, the remote control submarine Kaikō and the Nereus have been able to descend to these depths. However, as of March 25, 2012 one vehicle, the Deepsea Challenger, had penetrated to a depth of 10,898 meters (35,756 ft).
+
+== Ecosystem ==
+The relative sparsity of primary producers means that the majority of organisms living in the abyssal zone depend on the marine snow that falls from oceanic layers above. The biomass of the abyssal zone actually increases near the seafloor as most of the decomposing material and decomposers rest on the seabed.
+The composition of the abyssal plain depends on the depth of the sea floor. Above 4000 meters the seafloor usually consists of calcareous shells of foraminifera, zooplankton, and phytoplankton. At depths greater than 4000 meters shells dissolve, leaving behind a seafloor of brown clay and silica from dead zooplankton and phytoplankton. Chemosynthetic bacteria support large and diverse communities near hydrothermal vents, filling a similar role in these ecosystems as plants do in the sunlit regions above.
+Manganese nodules, which are found in some areas of the deep sea, have been proposed to produce oxygen by a team of researchers from the Scottish Society of Marine Sciences. They observed rising oxygen concentrations in some experiments with manganese nodules present. However, there are significant problems with the research, including that manganese nodules were not present in some of the experiments, and no other researchers have been able to replicate the result.
+
+== Biological adaptations ==
+Organisms that live at this depth have had to evolve to overcome challenges provided by the abyssal zone. Fish and invertebrates had to evolve to withstand the sheer cold and intense pressure found at this level. Not only did they have to find ways to hunt and survive in constant darkness, but they also had to thrive in an ecosystem that has less oxygen and biomass, energy sources and prey, than the upper zones. To survive in these conditions, many fish and other organisms developed a much slower metabolism, and require much less oxygen than those in upper zones. Many animals also move very slowly to conserve energy. Their reproduction rates are also very slow, to decrease competition and conserve energy. Animals here typically have flexible stomachs and mouths, so that when scarce prey are found they can consume as many as possible.
+
+Other challenges faced by life in the abyssal zone are the pressure and darkness caused by the zone's depth. Many organisms living in this zone have evolved to minimize internal air spaces, such as swim bladders. This adaptation helps to protect them from the extreme pressure, which can reach around 75 MPa (11,000 psi). The absence of light also spawned many different adaptations, such as having large eyes and the ability to produce their own light (bioluminescence). Large eyes would allow the detection and use of any light available, no matter how small. Commonly, animals in the abyssal zone are bioluminescent, producing blue light, because light in the blue wavelength range is attenuated over greater travel distances than other wavelengths. Due to this lack of light, complex patterns and bright colors are not needed. Most fish species have evolved to be transparent, red, or black so that they better blend in with the darkness and do not waste energy on developing and maintaining bright or complex patterns.

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+title: "Abyssal zone"
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+
+== Animals ==
+The abyssal zone is made up of many different types of organisms, including microorganisms, crustaceans, molluscs (bivalves, snails, and cephalopods), different classes of fishes, and possibly some animals that have yet to be discovered. Most of the fish species in this zone are described as demersal or benthopelagic fishes. Demersal fish are fish whose habitats are on or near (typically less than five meters from) the seafloor. Most fish species fit into that classification, because the seafloor contains most of the abyssal zone's nutrients; therefore, the most complex food web or greatest biomass would be in this region of the zone.
+Organisms in the abyssal zone rely on the natural processes of higher ocean layers. When animals from higher ocean levels die, their carcasses occasionally drift down to the abyssal zone, where organisms in the deep can feed on them. When a whale carcass falls down to the abyssal zone, this is called a whale fall. The carcass of the whale can create complex ecosystems for organisms in the depths.
+Benthic organisms in the abyssal zone would need to have evolved morphological traits that could either keep them out of oxygen-depleted water above the sea floor or enable them to extract oxygen from the water above, while also allowing the animal access to the seafloor and the nutrients located there. There are also animals that spend their time in the upper portion of the abyssal zone, some of which even occasionally spend time in the zone directly above, the bathyal zone. While there are a number of different fish species representing many different groups and classes, like Actinopterygii (ray-finned fish), there are no known members of the class Chondrichthyes (animals such as sharks, rays, and chimaeras) that make the abyssal zone their primary or constant habitat. Whether this is due to the limited resources, energy availability, or other physiological constraints is unknown. Most Chondrichthyes species only go as deep as the bathyal zone.
+Creatures that live in the abyssal zone include:
+   
+
+Tripod fish (Bathypterois grallator): their habitat is along the ocean floor, usually around 4,720 m below sea level. Their pelvic fins and caudal fin have long bony rays protruding from them. They face the current while standing still on their long rays. Once they sense food nearby, they use their large pectoral fins to hit the unsuspecting prey towards their mouth. Each member of this species has both male and female reproductive organs so that if a mate cannot be found, they can self-fertilize.
+Dumbo octopus: this octopus usually lives at a depth between 1,000 and 7,000 meters, deeper than any other known octopus. They use the fins on top of their head, which look like flapping ears, to hover over the sea floor looking for food. They use their arms to help change directions or crawl along the seafloor. To combat the intense pressure of the abyssal zone, this octopus species lost its ink sac during evolution. They also use their strand-like structured suction cups to help detect predators, food, and other aspects of their environment.
+Cusk eel (genus Bassozetus): there are no known fish that live at depths greater than the cusk eel. The depth of the cusk eel habitat can be as great as 8,370 meters below sea level. This animal's ventral fins are specialized forked barbel-like organs that act as sensory organs. Cusk eels produce sounds to mate. Male cusk eels have two pairs of sonic muscles, while female cusk eels have three.
+Abyssal grenadier: this resident of the abyssal zone is known to live at depths ranging from 800 and 4,000 meters. It has extremely large eyes, but a small mouth. It is thought to be a semelparous species, meaning it only reproduces once and then dies. This is seen as a way for the organism to conserve energy and have a higher chance of having some healthy strong children. This reproductive strategy could be very useful in low energy environments such as the abyssal zone.
+Pseudoliparis swirei: the Mariana snailfish, or Mariana hadal snailfish, is a species of snailfish found at hadal depths in the Mariana Trench in the western Pacific Ocean. It is known from a depth range of 6,198–8,076 m (20,335–26,496 ft), including a capture at 7,966 m (26,135 ft), which is possibly the record for a fish caught on the seafloor.

data/en.wikipedia.org/wiki/Abyssal_zone-2.md

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+---
+title: "Abyssal zone"
+chunk: 3/3
+source: "https://en.wikipedia.org/wiki/Abyssal_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:16.154926+00:00"
+instance: "kb-cron"
+---
+
+== Environmental concerns ==
+Climate change has had negative effects on the abyssal zone. Due to the zone's depth, increasing global temperatures do not affect it as quickly or drastically as the rest of the world, but the zone is still afflicted by ocean acidification. Pollutants, such as plastics, are also present in this zone. Plastics are especially bad for the abyssal zone because these organisms have evolved to eat or try to eat anything that moves or appears to be detritus, resulting in organisms consuming plastics instead of nutrients. Both ocean acidification and pollution are decreasing the already small biomass that resides within the abyssal zone.
+Another problem caused by humans is overfishing. Even though no fishery can fish for organisms anywhere near the abyssal zone, they can still cause harm in deeper waters. The abyssal zone depends on dead organisms from the upper zones sinking to the seafloor, since the ecosystem lacks producers due to a lack of sunlight. As fish and other animals are removed from the ocean, the frequency and amount of dead material reaching the abyssal zone decreases.
+Deep sea mining operations could cause problems for the abyssal zone in the future. The talks and planning for this industry are already under way. Deep sea mining could be disastrous for this extremely fragile ecosystem since there are many ecological dangers posed by mining for deep sea minerals. Mining could increase the amount of pollution not only in the abyssal zone, but in the ocean as a whole, and would physically destroy habitats and the seafloor.
+Sediment plumes generated by mining activities can spread widely, affecting filter feeders and smothering marine life. The potential release of toxic chemicals and heavy metals from mining equipment and disturbed seabed materials could lead to chemical pollution, while noise from machinery can disrupt the behavior and communication of marine animals. Physical disturbances to the seabed may destroy geological features and their associated ecosystems. Furthermore, changes in water quality and the disruption of carbon sequestration processes, where organic carbon is stored in the deep sea, could have broader environmental impacts, including contributing to climate change. The slow rate of change in deep-sea environments and the long lifespans and reproductive cycles of abyssal species mean that recovery from such disturbances could take decades or centuries.
+
+== See also ==
+
+Abyssal plain
+Beebe Hydrothermal Vent Field
+Deep sea
+Deep sea community
+Deep-sea fish    
+Mariana Trench
+
+== References ==

data/en.wikipedia.org/wiki/Albufera_(lagoon)-0.md

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+---
+title: "Albufera (lagoon)"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Albufera_(lagoon)"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:17.363720+00:00"
+instance: "kb-cron"
+---
+
+Albufera (Catalan/Valencian, 'lagoon') is the name of several estuarine lagoons in Spain:
+
+Albufera de València, on the Gulf of Valencia
+Albufera Natural Park, Natural Park in Valencia
+Albufera de Gaianes, in Gaianes (province of Alicante)
+S'Albufera de Mallorca, on the island of Mallorca
+S'Albufereta, also on Mallorca
+S'Albufera des Grau, on Menorca
+
+
+== See also ==
+Albufeira, a city in Portugal

data/en.wikipedia.org/wiki/Archipelago-0.md

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+---
+title: "Archipelago"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Archipelago"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:18.531660+00:00"
+instance: "kb-cron"
+---
+
+An archipelago (  AR-kə-PEL-ə-goh), sometimes called an island group or island chain, is a chain, cluster, or collection of islands. An archipelago may be in an ocean, a sea, or a smaller body of water. Examples of archipelagos include the Aegean Islands (the origin of the term archipelago), the Canadian Arctic Archipelago, the Stockholm Archipelago, the Malay Archipelago (which includes the Indonesian and Philippine Archipelagos), the Lucayan (Bahamian) Archipelago, the Japanese archipelago, the Hawaiian Archipelago, and the Galapagos.
+
+
+== Etymology ==
+The word archipelago is derived from the Italian arcipelago (used as a proper name for the Aegean Sea), itself perhaps a deformation of the Greek Αιγαίον Πέλαγος. Usage later shifted to refer to the Aegean Islands (since the sea has a large number of islands). The erudite paretymology, deriving the word from Ancient Greek ἄρχι- (arkhi-, "chief") and πέλαγος (pélagos, "sea"), proposed by Buondelmonti, can still be found.
+
+
+== Geographic types ==
+Archipelagos may be found isolated in large bodies of water or neighboring a large land mass. For example, Scotland has more than 700 islands surrounding its mainland, which form an archipelago.
+Depending on their geological origin, islands forming archipelagos can be referred to as oceanic islands, continental fragments, or continental islands.
+
+
+=== Oceanic islands ===
+Oceanic islands are formed by volcanoes erupting from the ocean floor. The Hawaiian Islands and Galapagos Islands in the Pacific, and Mascarene Islands in the south Indian Ocean are examples.
+
+
+=== Continental fragments ===
+Continental fragments are islands that were once part of a continent, and became separated due to natural disasters. The fragments may also be formed by moving glaciers which cut out land, which then fills with water. The Farallon Islands off the coast of California are examples of continental fragment islands.
+
+
+=== Coral cay archipelago ===
+A coral cay archipelago is formed when ocean currents transport sediments that gradually build up on coral reefs. The Florida Keys are one example.
+
+
+=== Continental islands ===
+
+Continental islands are islands that were once part of a continent and still sit on the continental shelf, which is the edge of a continent that lies under the ocean. The islands of the Inside Passage off the coast of British Columbia and the Canadian Arctic Archipelago are examples.
+
+
+=== Artificial archipelagos ===
+Artificial archipelagos have been created in various countries for different purposes. Palm Islands and The World Islands in Dubai were or are being created for leisure and tourism purposes. Marker Wadden in the Netherlands is being built as a conservation area for birds and other wildlife.
+
+
+== Superlatives ==
+The largest archipelago in the world by number of islands is the Archipelago Sea, which is part of Finland. There are approximately 40,000 islands, most being uninhabited. The largest archipelagic state in the world by area with more than 17,500 islands, and by population of around 284 million people, is Indonesia.
+
+
+== See also ==
+
+List of landforms
+List of archipelagos by number of islands
+List of archipelagos
+Archipelagic state
+List of islands
+Aquapelago
+
+
+== References ==
+
+
+== External links ==
+
+Chisholm, Hugh, ed. (1911). "Archipelago" . Encyclopædia Britannica (11th ed.). Cambridge University Press.
+30 Most Incredible Island Archipelagos

data/en.wikipedia.org/wiki/Atoll-0.md

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+---
+title: "Atoll"
+chunk: 1/2
+source: "https://en.wikipedia.org/wiki/Atoll"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:19.794424+00:00"
+instance: "kb-cron"
+---
+
+An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most of the approximately 440 atolls in the world are in the Pacific Ocean.
+Two different, well-cited models, the subsidence model and the antecedent karst model, have been used to explain the development of atolls. According to Charles Darwin's subsidence model, the formation of an atoll is explained by the sinking of a volcanic island around which a coral fringing reef has formed. Over geologic time, the volcanic island becomes extinct and eroded as it subsides completely beneath the surface of the ocean. As the volcanic island subsides, the coral fringing reef becomes a barrier reef that is detached from the island. Eventually, the reef and the small coral islets on top of it are all that is left of the original island, and a lagoon has taken the place of the former volcano. The lagoon is not the former volcanic crater. For the atoll to persist, the coral reef must be maintained at the sea surface, with coral growth matching any relative change in sea level (sinking of the island or rising oceans).
+An alternative model for the origin of atolls is called the antecedent karst model. In the antecedent karst model, the first step in the formation of an atoll is the development of a flat top, mound-like coral reef during the subsidence of an oceanic island of either volcanic or nonvolcanic origin below sea level. Then, when relative sea level drops below the level of the flat surface of coral reef, it is exposed to the atmosphere as a flat topped island which is dissolved by rainfall to form limestone karst. Because of hydrologic properties of this karst, the rate of dissolution of the exposed coral is lowest along its rim and the rate of dissolution increases inward to its maximum at the center of the island. As a result, a saucer shaped island with a raised rim forms. When relative sea level submerges the island again, the rim provides a rocky core on which coral grow again to form the islands of an atoll and the flooded bottom of the saucer forms the lagoon within them.
+
+== Usage ==
+The word atoll comes from the Dhivehi word atholhu (އަތޮޅު, pronounced [ˈat̪oɭu]). Dhivehi is an Indo-Aryan language spoken in the Maldives. The word's first recorded English use was in 1625 as atollon. Charles Darwin coined the term in his monograph, The Structure and Distribution of Coral Reefs. He recognized the word's indigenous origin and defined it as a "circular group of coral islets", synonymously with "lagoon-island".
+More modern definitions of atoll describe them as "annular reefs enclosing a lagoon in which there are no promontories other than reefs and islets composed of reef detritus" or "in an exclusively morphological sense, [as] a ring-shaped ribbon reef enclosing a lagoon".
+
+== Distribution and size ==
+There are approximately 440 atolls in the world. Most of the world's atolls are in the Pacific Ocean (with concentrations in the Caroline Islands, the Coral Sea Islands, the Marshall Islands, the Tuamotu Islands, Kiribati, Tokelau, and Tuvalu) and the Indian Ocean (the Chagos Archipelago, Lakshadweep, the atolls of the Maldives, and the Outer Islands of Seychelles). In addition, Indonesia also has several atolls spread across the archipelago, such as in the Thousand Islands, Taka Bonerate Islands, and atolls in the Raja Ampat Islands. The Atlantic Ocean has no large groups of atolls, other than eight atolls east of Nicaragua that belong to the Colombian department of San Andres and Providencia in the Caribbean.
+Reef-building corals will thrive only in warm tropical and subtropical waters of oceans and seas, and therefore atolls are found only in the tropics and subtropics. The northernmost atoll in the world is Kure Atoll at 28°25′ N, along with other atolls of the Northwestern Hawaiian Islands. The southernmost atolls in the world are Elizabeth Reef at 29°57′ S, and nearby Middleton Reef at 29°27′ S, in the Tasman Sea, both of which are part of the Coral Sea Islands Territory. The next southerly atoll is Ducie Island in the Pitcairn Islands Group, at 24°41′ S. 
+The atoll closest to the Equator is Aranuka of Kiribati. Its southern tip is just 13 km (8 mi) north of the Equator.
+Bermuda is sometimes claimed as the "northernmost atoll" at a latitude of 32°18′ N. At this latitude, coral reefs would not develop without the warming waters of the Gulf Stream. However, Bermuda is termed a pseudo-atoll because its general form, while resembling that of an atoll, has a very different origin of formation.
+In most cases, the land area of an atoll is very small in comparison to the total area. Atoll islands are low lying, with their elevations less than 5 metres (16 ft). Measured by total area, Lifou (1,146 km2, 442 sq mi) is the largest raised coral atoll of the world, followed by Rennell Island (660 km2, 250 sq mi). More sources, however, list Kiritimati as the largest atoll in the world in terms of land area. It is also a raised coral atoll (321 km2, 124 sq mi land area; according to other sources even 575 km2, 222 sq mi), 160 km2 (62 sq mi) main lagoon, 168 km2 (65 sq mi) other lagoons (according to other sources 319 km2, 123 sq mi total lagoon size).
+The geological formation known as a reef knoll refers to the elevated remains of an ancient atoll within a limestone region, appearing as a hill. The second largest atoll by dry land area is Aldabra, with 155 km2 (60 sq mi). Huvadhu Atoll, situated in the southern region of the Maldives, holds the distinction of being the largest atoll based on the sheer number of islands it comprises, with a total of 255 individual islands.

data/en.wikipedia.org/wiki/Atoll-1.md

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+---
+title: "Atoll"
+chunk: 2/2
+source: "https://en.wikipedia.org/wiki/Atoll"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:19.794424+00:00"
+instance: "kb-cron"
+---
+
+=== List of atolls ===
+
+=== Gallery ===
+
+== Formation ==
+
+In 1842, Charles Darwin explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a five-year voyage aboard HMS Beagle from 1831 to 1836. Darwin's explanation suggests that several tropical island types: from high volcanic island, through barrier reef island, to atoll, represented a sequence of gradual subsidence of what started as an oceanic volcano. He reasoned that a fringing coral reef surrounding a volcanic island in the tropical sea will grow upward as the island subsides (sinks), becoming an "almost atoll", or barrier reef island, as typified by an island such as Aitutaki in the Cook Islands, and Bora Bora and others in the Society Islands. The fringing reef becomes a barrier reef for the reason that the outer part of the reef maintains itself near sea level through biotic growth, while the inner part of the reef falls behind, becoming a lagoon because conditions are less favorable for the coral and calcareous algae responsible for most reef growth. In time, subsidence carries the old volcano below the ocean surface and the barrier reef remains. At this point, the island has become an atoll.
+As formulated by J. E. Hoffmeister, F. S. McNeil, E. G. Prudy, and others, the antecedent karst model argues that atolls are Pleistocene features that are the direct result of the interaction between subsidence and preferential karst dissolution that occurred in the interior of flat topped coral reefs during exposure during glacial lowstands of sea level. The elevated rims along an island created by this preferential karst dissolution become the sites of coral growth and islands of atolls when flooded during interglacial highstands.
+The research of A. W. Droxler, Stéphan J Jorry and others supports the antecedent karst model as they found that the morphology of modern atolls are independent of any influence of an underlying submerged and buried island and are not rooted to an initial fringing reef/barrier reef attached to a slowly subsiding volcanic edifice. In fact, the Neogene reefs underlying the studied modern atolls overlie and completely bury the subsided island are all non-atoll, flat-topped reefs. In fact, they found that atolls did not form doing the subsidence of an island until MIS-11, Mid-Brunhes, long after the many the former islands had been completely submerged and buried by flat topped reefs during the Neogene.
+Atolls are the product of the growth of tropical marine organisms, and so these islands are found only in warm tropical waters. Volcanic islands located beyond the warm water temperature requirements of hermatypic (reef-building) organisms become seamounts as they subside, and are eroded away at the surface. An island that is located where the ocean water temperatures are just sufficiently warm for upward reef growth to keep pace with the rate of subsidence is said to be at the Darwin Point. Islands in colder, more polar regions evolve toward seamounts or guyots; warmer, more equatorial islands evolve toward atolls, for example Kure Atoll. However, ancient atolls during the Mesozoic appear to exhibit different growth and evolution patterns.
+
+Coral atolls are important as sites where dolomitization of calcite occurs. Several models have been proposed for the dolomitization of calcite and aragonite within them. They are the evaporative, seepage-reflux, mixing-zone, burial, and seawater models. Although the origin of replacement dolomites remains problematic and controversial, it is generally accepted that seawater was the source of magnesium for dolomitization and the fluid in which calcite was dolomitized to form the dolomites found within atolls. Various processes have been invoked to drive large amounts of seawater through an atoll in order for dolomitization to occur.
+
+== Royal Society expeditions 1896–98 ==
+
+In 1896, 1897 and 1898, the Royal Society of London carried out drilling on Funafuti atoll in Tuvalu for the purpose of investigating the formation of coral reefs. They wanted to determine whether traces of shallow water organisms could be found at depth in the coral of Pacific atolls. This investigation followed the work on the structure and distribution of coral reefs conducted by Charles Darwin in the Pacific.
+The first expedition in 1896 was led by William Johnson Sollas of the University of Oxford. Geologists included Walter George Woolnough and Edgeworth David of the University of Sydney. David led the expedition in 1897. The third expedition in 1898 was led by Alfred Edmund Finckh.
+
+== See also ==
+
+Baratal limestone, sometimes described as the oldest known atoll
+Coral island
+
+== References ==
+
+=== Inline citations ===
+
+=== Sources ===
+Dobbs, David (2005). Reef Madness: Charles Darwin, Alexander Agassiz, and the Meaning of Coral.  Pantheon. ISBN 0-375-42161-0.
+Fairbridge, R. W. (July 1950). "Recent and Pleistocene Coral Reefs of Australia". J. Geol., 58(4: Reef Issue): 330–401. Bibcode:1950JG.....58..330F. doi:10.1086/625751. JSTOR 30070464.
+McNeil, F. S. (July 1954). "Organic Reefs and Banks and Associated Detrital Sediments". Amer. J. Sci., 252(7): 385–401. doi:10.2475/ajs.252.7.385.
+
+== External links ==
+
+Formation of Bermuda reefs
+Darwin's Volcano – A short video discussing Darwin and Agassiz' coral reef formation debate
+NOAA National Ocean Service Education – Coral Atoll Animation
+NOAA National Ocean Service – What are the three main types of coral reefs?
+Research Article: Predicting Coral Recruitment in Palau's Complex Reef Archipelago; Archived 2021-09-20 at the Wayback Machine
+World Atolls, Goldberg 2016: A global map containing all atolls

data/en.wikipedia.org/wiki/Barrier_island-0.md

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+---
+title: "Barrier island"
+chunk: 1/4
+source: "https://en.wikipedia.org/wiki/Barrier_island"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:21.177659+00:00"
+instance: "kb-cron"
+---
+
+Barrier islands are a coastal landform, a type of dune system and sand island, where an area of sand off the coast has been formed by wave and tidal action parallel to the mainland coast.  Barrier islands are commonly formed in long, narrow systems parallel to shorelines and are shaped by waves, tides, sediment movement, and sea-level change, which cause them to shift, grow, or erode over time. They protect coastlines by absorbing energy, and create areas of protected waters where wetlands may flourish. A barrier chain may extend for hundreds of kilometers, with islands periodically separated by tidal inlets. The longest barrier island in the world is Padre Island of Texas, United States, at 113 miles (182 km) long. Sometimes an important inlet may close permanently, transforming an island into a barrier peninsula, often including a barrier beach. Barrier islands are related to other coastal landforms such as barrier beaches and spits, which share similar physical features but differ primarily in their degree of attachment to the mainland and the presence of water on their landward side. Though many are long and narrow, the length and width of barriers and overall morphology of barrier coasts are related to parameters including tidal range, wave energy, sediment supply, sea-level trends, and basement controls. The amount of vegetation on the barrier has a large impact on the height and evolution of the island.
+Globally, there have been approximately 1,500 barrier islands identified, totaling over 15,000 kilometers in combined length. Barrier islands are most abundant in the northern hemisphere with North America accounting for over one-third of the barrier islands and Asia nearing one-quarter of the total.
+There are chains of barrier islands along approximately 13 to 15% of the world's coastlines. They display different settings, suggesting that they can form and be maintained in a variety of environments. Numerous theories have been proposed to explain their formation.
+A human-made offshore coastal engineering structure constructed parallel to the shore is called a breakwater. Its coastal morphodynamic effect is to dissipate and reduce the energy of the waves and currents striking the coast in the same way as a naturally occurring barrier island.
+
+== Constituent parts ==
+Barrier islands function as part of an interconnected coastal system where environments exchange both sediment and energy, where changes to one component can influence the entire barrier system. 
+
+Upper shoreface
+The shoreface is the part of the barrier where the ocean reaches the shore of the island. The barrier island body itself separates the shoreface from the backshore and lagoon/tidal flat area. Characteristics common to the upper shoreface are fine sands with mud and possibly silt. Further out into the ocean the sediment becomes finer. The effect of waves at this point is weak because of the depth. Bioturbation is common and many fossils can be found in upper shoreface deposits in the geologic record.
+
+Middle shoreface
+The middle shoreface is located in the upper shoreface. The middle shoreface is strongly influenced by wave movement because of its depth. Closer to shore the sand is medium-grained, with shell pieces common. Since wave action is heavier, bioturbation is not likely.
+
+Lower shoreface
+The lower shoreface is constantly affected by wave action. This results in development of herringbone sedimentary structures because of the constant differing flow of waves. The sand is coarser.
+
+Foreshore
+The foreshore is the area on land between high and low tide. Like the upper shoreface, it is constantly affected by wave action. Cross-bedding and lamination are present and coarser sands are present because of the high energy present by the crashing of the waves. The sand is also very well sorted.
+
+Backshore
+The backshore is always above the highest water level point. The berm is also found here which marks the boundary between the foreshore and backshore. Wind is the important factor here, not water. During strong storms high waves and wind can deliver and erode sediment from the backshore.
+
+Dunes
+Coastal dunes, created by wind, are typical of a barrier island. They are located at the top of the backshore. The dunes will display characteristics of typical aeolian wind-blown dunes. The difference is that dunes on a barrier island typically contain coastal vegetation roots and marine bioturbation. They also help Barrier Islands grow.
+
+Lagoon and tidal flats
+The lagoon and tidal flat area is located behind the dune and backshore area. Here the water is still, which allows fine silts, sands, and mud to settle out. Lagoons can become host to an anaerobic environment. This will allow high amounts of organic-rich mud to form. Vegetation is also common.
+
+== Processes ==
+
+=== Migration and overwash ===
+Water levels may be higher than the island during storm events. This situation can lead to overwash, which brings sand from the front of the island to the top and/or landward side of the island. During these washover events, the sand that is being transported may end up on the landward side, beyond the dune, forming a washover fan. The overwash can continuously alter the surface of the barrier, requiring the ecosystem to adapt to periodic disturbances. This process leads to the evolution and migration of the barrier island.
+
+==== Types of migration ====
+Barrier island systems are dynamic and they may shift positions over time through three main types of migration. Lateral migration happens when sand is pushed along the coast, causing erosion at one end and accumulations at the other. This results in sideways movement along the shoreline. Prograding/regressive migration is when sand builds up on the ocean-facing side of the barrier island, leading to growth on the seaward side. Transgression migration occurs when the barrier island is being built up toward the mainland. This is commonly caused by the sea levels rising or the land sinking.

data/en.wikipedia.org/wiki/Barrier_island-1.md

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+---
+title: "Barrier island"
+chunk: 2/4
+source: "https://en.wikipedia.org/wiki/Barrier_island"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:21.177659+00:00"
+instance: "kb-cron"
+---
+
+=== Critical width concept ===
+Barrier islands are often formed to have a certain width. The term "critical width concept" has been discussed with reference to barrier islands, overwash, and washover deposits since the 1970s. The concept basically states that overwash processes were effective in migration of the barrier only where the barrier width is less than a critical value. The island did not narrow below these values because overwash was effective at transporting sediment over the barrier island, thereby keeping pace with the rate of ocean shoreline recession. Sections of the island with greater widths experienced washover deposits that did not reach the bayshore, and the island narrowed by ocean shoreline recession until it reached the critical width. The only process that widened the barrier beyond the critical width was breaching, formation of a partially subaerial flood shoal, and subsequent inlet closure.
+Critical barrier width can be defined as the smallest cross-shore dimension that minimizes net loss of sediment from the barrier island over the defined project lifetime. The magnitude of critical width is related to sources and sinks of sand in the system, such as the volume stored in the dunes and the net long-shore and cross-shore sand transport, as well as the island elevation. The concept of critical width is important for large-scale barrier island restoration, in which islands are reconstructed to optimum height, width, and length for providing protection for estuaries, bays, marshes and mainland beaches.
+
+== Location ==
+
+Barrier Islands can be observed on every continent on Earth, except Antarctica. They occur primarily in areas that are tectonically stable, such as "trailing edge coasts" facing (moving away from) ocean ridges formed by divergent boundaries of tectonic plates, and around smaller marine basins such as the Mediterranean Sea and the Gulf of Mexico. Areas with relatively small tides and ample sand supply favor barrier island formation.
+
+=== Australia ===
+Moreton Bay, on the east coast of Australia and directly east of Brisbane, is sheltered from the Pacific Ocean by a chain of very large barrier islands. Running north to south they are Bribie Island, Moreton Island, North Stradbroke Island and South Stradbroke Island (the last two used to be a single island until a storm created a channel between them in 1896). North Stradbroke Island is the second largest sand island in the world and Moreton Island is the third largest.
+K'gari (formerly known as Fraser Island), another barrier island lying 200 km north of Moreton Bay on the same coastline, is the largest sand island in the world.
+
+=== United States ===
+Barrier islands are found most prominently on the United States' East and Gulf Coasts, where every state, from Maine to Florida (East Coast) and from Florida to Texas (Gulf coast), features at least part of a barrier island. Many have large numbers of barrier islands; Florida, for instance, had 29 (in 1997) in just 300 kilometres (190 mi) along the west (Gulf) coast of the Florida peninsula, plus about 20 others on the east coast and several barrier islands and spits along the panhandle coast. Padre Island, in Texas, is the world's longest barrier island; other well-known islands on the Gulf Coast include Galveston Island in Texas and Sanibel and Captiva Islands in Florida. Those on the East Coast include Miami Beach and Palm Beach in Florida; Hatteras Island in North Carolina; Assateague Island in Virginia and Maryland; Absecon Island in New Jersey, where Atlantic City is located; and Jones Beach Island and Fire Island, both off Long Island in New York. No barrier islands are found on the Pacific Coast of the United States due to the rocky shore and short continental shelf, but barrier peninsulas can be found. Barrier islands can also be seen on Alaska's Arctic coast.
+
+=== Canada ===
+Barrier Islands can also be found in Maritime Canada, and other places along the coast. A good example is found at Miramichi Bay, New Brunswick, where Portage Island as well as Fox Island and Hay Island protect the inner bay from storms in the Gulf of Saint Lawrence.
+
+=== Mexico ===
+Mexico's Gulf of Mexico coast has numerous barrier islands and barrier peninsulas.
+
+=== New Zealand ===
+Barrier islands are more prevalent in the north of both of New Zealand's main islands. Notable barrier islands in New Zealand include Matakana Island, which guards the entrance to Tauranga Harbour, and Rabbit Island, at the southern end of Tasman Bay. See also Nelson Harbour's Boulder Bank, below.
+
+=== India ===
+The Vypin Island in the Southwest coast of India in Kerala is 27 km long. It is also one of the most densely populated islands in the world.
+
+=== Indonesia ===
+The Indonesian Barrier Islands lie off the western coast of Sumatra. From north to south along this coast they include Simeulue, the Banyak Islands (chiefly Tuangku and Bangkaru), Nias, the Batu Islands (notably Pini, Tanahmasa and Tanahbala), the Mentawai Islands (mainly Siberut, Sipura, North Pagai and South Pagai Islands) and Enggano Island. 
+
+=== Europe ===
+Barrier islands can be observed in the Baltic Sea from Poland to Lithuania as well as distinctly in the Wadden Islands, which stretch from the Netherlands to Denmark. Lido di Venezia and Pellestrina are notable barrier islands of the Lagoon of Venice which have for centuries protected the city of Venice in Italy. Chesil Beach on the south coast of England developed as a barrier beach. Barrier beaches are also found in the north of the Azov and Black seas.
+
+== Formation theories ==

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+---
+title: "Barrier island"
+chunk: 3/4
+source: "https://en.wikipedia.org/wiki/Barrier_island"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:21.177659+00:00"
+instance: "kb-cron"
+---
+
+Scientists have proposed numerous explanations for the formation of barrier islands for more than 150 years. There are three major theories: offshore bar, spit accretion, and submergence. No single theory can explain the development of all barriers, which are distributed extensively along the world's coastlines. Scientists accept the idea that barrier islands, including other barrier types, can form by a number of different mechanisms.
+There appears to be some general requirements for formation. Barrier island systems develop most easily on wave-dominated coasts with a small to moderate tidal range. Coasts are classified into three groups based on tidal range: microtidal, 0–2 meter tidal range; mesotidal, 2–4 meter tidal range; and macrotidal, >4 meter tidal range. Barrier islands tend to form primarily along microtidal coasts, where they tend to be well developed and nearly continuous. They are less frequently formed in mesotidal coasts, where they are typically short with tidal inlets common. Barrier islands are very rare along macrotidal coasts. Along with a small tidal range and a wave-dominated coast, there must be a relatively low gradient shelf. Otherwise, sand accumulation into a sandbar would not occur and instead would be dispersed throughout the shore. An ample sediment supply is also a requirement for barrier island formation. This often includes fluvial deposits and glacial deposits. The last major requirement for barrier island formation is a stable sea level. It is especially important for sea level to remain relatively unchanged during barrier island formation and growth. If sea level changes are too drastic, time will be insufficient for wave action to accumulate sand into a dune, which will eventually become a barrier island through aggradation. The formation of barrier islands requires a constant sea level so that waves can concentrate the sand into one location and build up to form the island.
+
+=== Offshore bar theory ===
+In 1845 the Frenchman Elie de Beaumont published an account of barrier formation. He believed that waves moving into shallow water churned up sand, which was deposited in the form of a submarine bar when the waves broke and lost much of their energy. As the bars developed vertically, they gradually rose above sea level, forming barrier islands.
+Several barrier islands have been observed forming by this process along the Gulf coast of the Florida peninsula, including: the North and South Anclote Bars associated with Anclote Key, Three Rooker Island, Shell Key, and South Bunces Key.
+
+=== Spit accretion theory ===
+American geologist Grove Karl Gilbert first argued in 1885 that the barrier sediments came from longshore sources. He proposed that sediment moving in the breaker zone through agitation by waves in longshore drift would construct spits extending from headlands parallel to the coast. The subsequent breaching of spits by storm waves would form barrier islands.
+
+=== Submergence theory ===
+
+William John McGee reasoned in 1890 that the East and Gulf coasts of the United States were undergoing submergence, as evidenced by the many drowned river valleys that occur along these coasts, including Raritan, Delaware and Chesapeake bays. He believed that during submergence, coastal ridges were separated from the mainland, and lagoons formed behind the ridges. He used the Mississippi–Alabama barrier islands (consists of Cat, Ship, Horn, Petit Bois and Dauphin Islands) as an example where coastal submergence formed barrier islands. His interpretation was later shown to be incorrect when the ages of the coastal stratigraphy and sediment were more accurately determined.
+Along the coast of Louisiana, former lobes of the Mississippi River delta have been reworked by wave action, forming beach ridge complexes. Prolonged sinking of the marshes behind the barriers has converted these former vegetated wetlands to open-water areas. In a period of 125 years, from 1853 to 1978, two small semi-protected bays behind the barrier developed as the large water body of Lake Pelto, leading to Isles Dernieres's detachment from the mainland.
+
+=== Boulder Bank ===
+An unusual natural structure in New Zealand may give clues to the formation processes of barrier islands. The Boulder Bank, at the entrance to Nelson Haven at the northern end of the South Island, is a unique 13 km-long stretch of rocky substrate a few metres in width. It is not strictly a barrier island, as it is linked to the mainland at one end. The Boulder Bank is composed of granodiorite from Mackay Bluff, which lies close to the point where the bank joins the mainland. It is still debated what process or processes have resulted in this odd structure, though longshore drift is the most accepted hypothesis. Studies have been conducted since 1892 to determine the speed of boulder movement. Rates of the top-course gravel movement have been estimated at 7.5 metres a year.
+
+== Types ==
+Barrier islands can be classified by their dominant coastal processes that influence their formation and change over time. 

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+---
+title: "Barrier island"
+chunk: 4/4
+source: "https://en.wikipedia.org/wiki/Barrier_island"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:21.177659+00:00"
+instance: "kb-cron"
+---
+
+=== Wave-dominated ===
+Wave-dominated barrier islands are long, low, and narrow, and usually are bounded by unstable inlets at either end. The presence of longshore currents caused by waves approaching the island at an angle will carry sediment long, extending the island. Longshore currents, and the resultant extension, are usually in one direction, but in some circumstances the currents and extensions can occur towards both ends of the island (as occurs on Anclote Key, Three Rooker Bar, and Sand Key, on the Gulf Coast of Florida). Washover fans on the lagoon side of barriers, where storm surges have over-topped the island, are common, especially on younger barrier islands. Wave-dominated barriers are also susceptible to being breached by storms, creating new inlets. Such inlets may close as sediment is carried in them by longshore currents, but may become permanent if the tidal prism (volumn and force of tidal flow) is large enough. Older barrier islands that have accumulated dunes are less subject to washovers and opening of inlets. Wave-dominated islands require an abundant supply of sediment to grow and develop dunes. If a barrier island does not receive enough sediment to grow, repeated washovers from storms will migrate the island towards the mainland.
+
+=== Mixed-energy ===
+
+Wave-dominated barrier islands may eventually develop into mixed-energy barrier islands. Mixed-energy barrier islands are molded by both wave energy and tidal flux. The flow of a tidal prism moves sand. Sand accumulates at both the inshore and off shore sides of an inlet, forming a flood delta or shoal on the bay or lagoon side of the inlet (from sand carried in on a flood tide), and an ebb delta or shoal on the open water side (from sand carried out by an ebb tide). Large tidal prisms tend to produce large ebb shoals, which may rise enough to be exposed at low tide. Ebb shoals refract waves approaching the inlet, locally reversing the longshore current moving sand along the coast. This can modify the ebb shoal into swash bars, which migrate into the end of the island up current from the inlet, adding to the barrier's width near the inlet (creating a "drumstick" barrier island). This process captures sand that is carried by the longshore current, preventing it from reaching the downcurrent side of the inlet, starving that island.
+Many of the Sea Islands in the U.S. state of Georgia are relatively wide compared to their shore-parallel length. Siesta Key, Florida has a characteristic drumstick shape, with a wide portion at the northern end near the mouth of Phillipi Creek.
+
+=== Fetch-Limited Barrier Islands ===
+Fetch-Limited barrier islands are defined by the difference in waves they are exposed to. These barrier islands are shaped by small, local waves that are on a smaller and lower-energy scale than barrier islands formed by open-ocean waves. These barrier islands are still formed in the same way as ocean-facing islands, but with much lower-energy. Fetch-limited barrier islands can be found all over the world, with over 63% coming from the Northern Hemisphere. North America  makes up the largest percentage, with just over 30% of all fetch-limited barrier islands.
+During fair-weather conditions, fetch-limited islands experience locally generated waves under one meter high. Because wave energy is low under these conditions, most significant geomorphic change occurs during storms. As a result, fetch-limited barrier islands are generally shorter and narrower than ocean-facing barriers. 
+
+== Ecological importance ==
+Barrier islands are critically important in mitigating ocean swells and other storm events for the water systems on the mainland side of the barrier island, as well as protecting the coastline. This effectively creates a unique environment of relatively low energy, brackish water. Multiple wetland systems such as lagoons, estuaries, and/or marshes can result from such conditions depending on the surroundings. They are typically rich habitats for a variety of flora and fauna. Without barrier islands, these wetlands could not exist; they would be destroyed by daily ocean waves and tides as well as ocean storm events. One of the most prominent examples is the Louisiana barrier islands.
+
+== See also ==
+
+North Frisian Barrier Island
+Outer Banks
+Virginia Barrier Islands
+New York Barrier Islands
+Texas barrier islands
+Sea Islands
+Long Beach Island
+Bald Head Island
+
+== Notes ==
+
+== References ==
+
+== Sources ==
+Davis, Richard A. Jr.; FitzGerald, Duncan M. (2004), Beaches and Coasts, United Kingdom: Blackwell Publishing, ISBN 978-0-632-04308-8
+Davis, Richard A. Jr. (2016). Barrier Islands of the Florida Gulf Coast Peninsula. Sarasota, Florida: Pineapple Press. ISBN 978-1-56164-8085.
+Morton, Robert A. (2007), "Historical Changes in the Mississippi-Alabama Barrier Islands and the Roles of Extreme Storms, Sea level, and human activities" (PDF), USGS Report, Open-File Report, U. S. Geological Survey: 43, Bibcode:2007usgs.rept...43M, doi:10.3133/ofr20071161
+
+== External links ==

data/en.wikipedia.org/wiki/Bay-0.md

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+---
+title: "Bay"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Bay"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:23.463029+00:00"
+instance: "kb-cron"
+---
+
+A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a narrow entrance. A fjord is an elongated bay formed by glacial action.
+The term embayment is also used for related features, such as extinct bays or freshwater environments.
+A bay can be the estuary of a river, such as the Chesapeake Bay, an estuary of the Susquehanna River. Bays may also be nested within each other; for example, James Bay is an arm of Hudson Bay in northeastern Canada. Some bays are large enough to have varied marine geology, such as the Bay of Bengal (2,600,000 km2 or 1,000,000 sq mi) and Hudson Bay (1,230,000 km2 or 470,000 sq mi).
+The land surrounding a bay often reduces the strength of winds and blocks waves. Bays may have as wide a variety of shoreline characteristics as other shorelines. In some cases, bays have beaches, which "are usually characterized by a steep upper foreshore with a broad, flat fronting terrace". Bays were significant in the history of human settlement because they provided easy access to marine resources like fisheries. Later they were important in the development of sea trade as the safe anchorage they provide encouraged their selection as ports.
+
+
+== Definition ==
+The United Nations Convention on the Law of the Sea defines a bay as a well-marked indentation in the coastline, whose penetration is in such proportion to the width of its mouth as to contain land-locked waters and constitute more than a mere curvature of the coast. An indentation, however, shall not be regarded as a bay unless its area is as large as (or larger than) that of the semi-circle whose diameter is a line drawn across the mouth of that indentation – otherwise, it would be referred to as a bight.
+
+
+=== Types ===
+
+Open – a bay that is widest at the mouth, flanked by headlands.
+Enclosed – a bay whose mouth is narrower than its widest part, flanked by at least one peninsula.
+Semi-enclosed – an open bay whose exit is made into narrower channels by one or more islands within its mouth.
+Back-barrier – a semi-enclosed bay separated from open water by one or more barrier islands or spits.
+Juridicial – a legal distinction defining a bay meeting certain criterion as inland waters, and thus the waters of a state, rather than international waters or the territorial waters of a national government a state may be sovereign to. Foremost among the criteria remains that the area impounded by the bay must be greater than that of a semicircle drawn across its mouth.Among the matters impacted by the definition are the right to the seabed and its minerals, control over fishing, the right of seafarers to innocent passage, and whether the affected coast is an international border or not.
+
+
+=== Gulf ===
+
+A gulf is a large inlet from an ocean or their seas into a landmass, larger and typically (though not always) with a narrower opening than a bay. The term was used traditionally for large, highly indented navigable bodies of salt water that are enclosed by the coastline. Many gulfs are major shipping areas, such as the Persian Gulf, Gulf of Mexico, Gulf of Finland, and Gulf of Aden.
+
+
+== Formation ==
+
+Bays form variously by plate tectonics, coastal erosion by rivers, and glaciers.
+The largest bays have developed through plate tectonics. As the  Paleozoic/early Mesozoic era super-continent Pangaea broke up along curved and indented fault lines, the continents moved apart and left large bays; these include the Gulf of Guinea, the Gulf of Mexico, and the Bay of Bengal, which is the world's largest bay.
+Bays also form through coastal erosion by rivers and glaciers. A bay formed by a glacier is a fjord. Rias are created by rivers and are characterised by more gradual slopes. Deposits of softer rocks erode more rapidly, forming bays, while harder rocks erode less quickly, leaving headlands.
+
+
+== See also ==
+Bay platform – Dead-end railway platform at a railway station that has through lines
+Great capes – Three major capes of the traditional clipper route
+List of gulfs
+
+
+== Notes ==
+
+
+== References ==

data/en.wikipedia.org/wiki/Beach-0.md

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+---
+title: "Beach"
+chunk: 1/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from rock, such as sand, gravel, shingle, pebbles, etc., or biological sources, such as mollusc shells or coralline algae. Sediments settle in different densities and structures, depending on the local wave action and weather, creating different textures, colors and gradients or layers of material.
+Though some beaches form on inland freshwater locations such as lakes and rivers, most beaches are in coastal areas where wave or current action deposits and reworks sediments. Erosion and changing of beach geologies happens through natural processes, like wave action and extreme weather events.  Where wind conditions are correct, beaches can be backed by coastal dunes which offer protection and regeneration for the beach.  However, these natural forces have become more extreme due to climate change, permanently altering beaches at very rapid rates. Some estimates describe as much as 50 percent of the earth's sandy beaches disappearing by 2100 due to climate-change driven sea level rise.
+Sandy beaches occupy about one third of global coastlines. These beaches are popular for recreation, playing important economic and cultural roles—often driving local tourism industries. To support these uses, some beaches have human-made infrastructure, such as lifeguard posts, changing rooms, showers, shacks and bars. They may also have hospitality venues (such as resorts, camps, hotels, and restaurants) nearby or housing, both for permanent and seasonal residents.
+Human forces have significantly changed beaches globally: direct impacts include bad construction practices on dunes and coastlines, while indirect human impacts include water pollution, plastic pollution and coastal erosion from sea level rise and climate change. Some coastal management practices are designed to preserve or restore natural beach processes, while some beaches are actively restored through practices like beach nourishment.
+Wild beaches, also known as undeveloped or undiscovered beaches, are not developed for tourism or recreation. Preserved beaches are important biomes with important roles in aquatic or marine biodiversity, such as for breeding grounds for sea turtles or nesting areas for seabirds or penguins. Preserved beaches and their associated dune are important for protection from extreme weather for inland ecosystems and human infrastructure.
+
+== Location and profile ==
+
+Although the seashore is most commonly associated with the word beach, beaches are also found by lakes and alongside large rivers.
+Beach may refer to:
+
+small systems where rock material moves onshore, offshore, or alongshore by the forces of waves and currents; or
+geological units of considerable size.
+The former are described in detail below; the larger geological units are discussed elsewhere under bars.
+There are several conspicuous parts to a beach that relate to the processes that form and shape it. The part mostly above water (depending upon tide), and more or less actively influenced by the waves at some point in the tide, is termed the beach berm. The berm is the deposit of material comprising the active shoreline. The berm has a crest (top) and a face—the latter being the slope leading down towards the water from the crest. At the very bottom of the face, there may be a trough, and further seaward one or more long shore bars: slightly raised, underwater embankments formed where the waves first start to break.
+The sand deposit may extend well inland from the berm crest, where there may be evidence of one or more older crests (the storm beach) resulting from very large storm waves and beyond the influence of the normal waves. At some point the influence of the waves (even storm waves) on the material comprising the beach stops, and if the particles are small enough (sand size or smaller), winds shape the feature. Where wind is the force distributing the grains inland, the deposit behind the beach becomes a dune.
+
+These geomorphic features compose what is called the beach profile. The beach profile changes seasonally due to the change in wave energy experienced during summer and winter months. In temperate areas where summer is characterised by calmer seas and longer periods between breaking wave crests, the beach profile is higher in summer.  The gentle wave action during this season tends to transport sediment up the beach towards the berm where it is deposited and remains while the water recedes.  Onshore winds carry it further inland forming and enhancing dunes.
+Conversely, the beach profile is lower in the storm season (winter in temperate areas) due to the increased wave energy, and the shorter periods between breaking wave crests. Higher energy waves breaking in quick succession tend to mobilise sediment from the shallows, keeping it in suspension where it is prone to be carried along the beach by longshore currents, or carried out to sea to form longshore bars, especially if the longshore current meets an outflow from a river or flooding stream.  The removal of sediment from the beach berm and dune thus decreases the beach profile.
+If storms coincide with unusually high tides, or with a freak wave event such as a tidal surge or tsunami which causes significant coastal flooding, substantial quantities of material may be eroded from the coastal plain or dunes behind the berm by receding water.  This flow may alter the shape of the coastline, enlarge the mouths of rivers and create new deltas at the mouths of streams that had not been powerful enough to overcome longshore movement of sediment.
+The line between beach and dune is difficult to define in the field. Over any significant period of time, sediment is always being exchanged between them. The drift line (the high point of material deposited by waves) is one potential demarcation. This would be the point at which significant wind movement of sand could occur, since the normal waves do not wet the sand beyond this area. However, the drift line is likely to move inland under assault by storm waves.
+
+== Formation ==

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+---
+title: "Beach"
+chunk: 2/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+Beaches are the result of wave action by which waves or currents move sand or other loose sediments of which the beach is made as these particles are held in suspension. Alternatively, sand may be moved by saltation (a bouncing movement of large particles). Beach materials come from erosion of rocks offshore, as well as from headland erosion and slumping producing deposits of scree. A coral reef offshore is a significant source of sand particles. Some species of fish that feed on algae attached to coral outcrops and rocks can create substantial quantities of sand particles over their lifetime as they nibble during feeding, digesting the organic matter, and discarding the rock and coral particles which pass through their digestive tracts.
+The composition of the beach depends upon the nature and quantity of sediments upstream of the beach, and the speed of flow and turbidity of water and wind. Sediments are moved by moving water and wind according to their particle size and state of compaction. Particles tend to settle and compact in still water.  Once compacted, they are more resistant to erosion.  Established vegetation (especially species with complex network root systems) will resist erosion by slowing the fluid flow at the surface layer. When affected by moving water or wind, particles that are eroded and held in suspension will increase the erosive power of the fluid that holds them by increasing the average density, viscosity, and volume of the moving fluid.
+Coastlines facing very energetic wind and wave systems will tend to hold only large rocks as smaller particles will be held in suspension in the turbid water column and carried to calmer areas by longshore currents and tides. Coastlines that are protected from waves and winds will tend to allow finer sediments such as clay and mud to precipitate creating mud flats and mangrove forests. The shape of a beach depends on whether the waves are constructive or destructive, and whether the material is sand or shingle. Waves are constructive if the period between their wave crests is long enough for the breaking water to recede and the sediment to settle before the succeeding wave arrives and breaks.
+Fine sediment transported from lower down the beach profile will compact if the receding water percolates or soaks into the beach. Compacted sediment is more resistant to movement by turbulent water from succeeding waves. Conversely, waves are destructive if the period between the wave crests is short. Sediment that remains in suspension when the following wave crest arrives will not be able to settle and compact and will be more susceptible to erosion by longshore currents and receding tides. The nature of sediments found on a beach tends to indicate the energy of the waves and wind in the locality.
+Constructive waves move material up the beach while destructive waves move the material down the beach. During seasons when destructive waves are prevalent, the shallows will carry an increased load of sediment and organic matter in suspension. On sandy beaches, the turbulent backwash of destructive waves removes material forming a gently sloping beach. On pebble and shingle beaches the swash is dissipated more quickly because the large particle size allows greater percolation, thereby reducing the power of the backwash, and the beach remains steep. Compacted fine sediments will form a smooth beach surface that resists wind and water erosion.
+During hot calm seasons, a crust may form on the surface of ocean beaches as the heat of the sun evaporates the water leaving the salt which crystallises around the sand particles.  This crust forms an additional protective layer that resists wind erosion unless disturbed by animals or dissolved by the advancing tide. Cusps and horns form where incoming waves divide, depositing sand as horns and scouring out sand to form cusps. This forms the uneven face on some sand shorelines. White sand beaches look white because the quartz or eroded limestone in the sand reflects or scatters sunlight without significantly absorbing any colors.
+
+=== Sand colors ===
+
+The composition of the sand varies depending on the local minerals and geology. Some of the types of sand found in beaches around the world are:
+
+White sand: Mostly made of quartz and limestone, it can also contain other minerals like feldspar and gypsum .
+Light-colored sand: This sand gets its color from quartz and iron, and is the most common sand color in Southern Europe and other regions of the Mediterranean Basin, such as Tunisia.
+Tropical white sand: On tropical islands, the sand is composed of calcium carbonate from the shells and skeletons of marine organisms, like corals and mollusks, as found in Aruba.
+Pink coral sand: Like the above, is composed of calcium carbonate and gets its pink hue from fragments of coral, such as in Bermuda and the Bahama Islands.
+Black sand: Black sand is composed of volcanic rock, like basalt and obsidian, which give it its gray-black color. Hawaii's Punaluu Beach, Madeira's Praia Formosa and Fuerteventura's Ajuy beach are examples of this type of sand.
+Red sand: This kind of sand is created by the oxidation of iron from volcanic rocks. Santorini's Kokkini Beach or the beaches on Prince Edward Island in Canada are examples of this kind of sand.
+Orange sand: Orange sand is high on iron. It can also be a combination of orange limestone, crushed shells, and volcanic deposits. Ramla Bay in Gozo, Malta or Porto Ferro in Sardinia are examples of each, respectively.
+Green sand: In this kind of sand, the mineral olivine has been separated from other volcanic fragments by erosive forces. A famous example is Hawaii's Papakolea Beach, which has sand containing basalt and coral fragments. Olivine beaches have a high potential for carbon sequestration, and artificial greensand beaches are being explored for this process by Project Vesta.
+
+== Erosion and accretion ==
+
+=== Natural erosion and accretion ===

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+---
+title: "Beach"
+chunk: 3/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+==== Causes ====
+Beaches are changed in shape chiefly by the movement of water and wind. Any weather event that is associated with turbid or fast-flowing water or high winds will erode exposed beaches. Longshore currents will tend to replenish beach sediments and repair storm damage. Tidal waterways generally change the shape of their adjacent beaches by small degrees with every tidal cycle. Over time these changes can become substantial leading to significant changes in the size and location of the beach.
+
+==== Effects on flora ====
+Changes in the shape of the beach may undermine the roots of large trees and other flora. Many beach adapted species (such as coconut palms) have a fine root system and large root ball which tends to withstand wave and wind action and tends to stabilize beaches better than other trees with a lesser root ball.
+
+==== Effects on adjacent land ====
+Erosion of beaches can expose less resilient soils and rocks to wind and wave action leading to undermining of coastal headlands eventually resulting in catastrophic collapse of large quantities of overburden into the shallows.  This material may be distributed along the beach front leading to a change in the habitat as sea grasses and corals in the shallows may be buried or deprived of light and nutrients.
+
+=== Humanmade erosion and accretion ===
+Coastal areas settled by man inevitably become subject to the effects of human-made structures and processes. Over long periods of time, these influences may substantially alter the shape of the coastline, and the character of the beach.
+
+==== Destruction of flora ====
+Beachfront flora plays a major role in stabilizing the foredunes and preventing beach head erosion and inland movement of dunes.  If flora with network root systems (creepers, grasses, and palms) are able to become established, they provide an effective coastal defense as they trap sand particles and rainwater and enrich the surface layer of the dunes, allowing other plant species to become established.  They also protect the berm from erosion by high winds, freak waves and subsiding floodwaters.
+Over long periods of time, well-stabilized foreshore areas will tend to accrete, while unstabilized foreshores will tend to erode, leading to substantial changes in the shape of the coastline.  These changes usually occur over periods of many years. Freak wave events such as tsunami, tidal waves, and storm surges may substantially alter the shape, profile and location of a beach within hours.
+Destruction of flora on the berm by the use of herbicides, excessive pedestrian or vehicle traffic, or disruption to freshwater flows may lead to erosion of the berm and dunes.  While the destruction of flora may be a gradual process that is imperceptible to regular beach users, it often becomes immediately apparent after storms associated with high winds and freak wave events that can rapidly move large volumes of exposed and unstable sand, depositing them further inland, or carrying them out into the permanent water forming offshore bars, lagoons or increasing the area of the beach exposed at low tide.
+Large and rapid movements of exposed sand can bury and smother flora in adjacent areas, aggravating the loss of habitat for fauna, and enlarging the area of instability. If there is an adequate supply of sand, and weather conditions do not allow vegetation to recover and stabilize the sediment, wind-blown sand can continue to advance, engulfing and permanently altering downwind landscapes.
+Sediment moved by waves or receding floodwaters can be deposited in coastal shallows, engulfing reed beds and changing the character of underwater flora and fauna in the coastal shallows.
+Burning or clearance of vegetation on the land adjacent to the beach head, for farming and residential development, changes the surface wind patterns, and exposes the surface of the beach to wind erosion.
+Farming and residential development are also commonly associated with changes in local surface water flows. If these flows are concentrated in stormwater drains emptying onto the beach head, they may erode the beach creating a lagoon or delta.
+Dense vegetation tends to absorb rainfall reducing the speed of runoff and releasing it over longer periods of time.  Destruction by burning or clearance of the natural vegetation tends to increase the speed and erosive power of runoff from rainfall.  This runoff will tend to carry more silt and organic matter from the land onto the beach and into the sea. If the flow is constant, runoff from cleared land arriving at the beach head will tend to deposit this material into the sand changing its color, odor and fauna.
+
+==== Creation of beach access points ====
+The concentration of pedestrian and vehicular traffic accessing the beach for recreational purposes may cause increased erosion at the access points if measures are not taken to stabilize the beach surface above high-water mark. Recognition of the dangers of loss of beach front flora has caused many local authorities responsible for managing coastal areas to restrict beach access points by physical structures or legal sanctions, and fence off foredunes in an effort to protect the flora.  These measures are often associated with the construction of structures at these access points to allow traffic to pass over or through the dunes without causing further damage.

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+---
+title: "Beach"
+chunk: 4/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+==== Concentration of runoff ====
+Beaches provide a filter for runoff from the coastal plain.  If the runoff is naturally dispersed along the beach, water borne silt and organic matter will be retained on the land and will feed the flora in the coastal area.  Runoff that is dispersed along the beach will tend to percolate through the beach and may emerge from the beach at low tide.
+The retention of the freshwater may also help to maintain underground water reserves and will resist salt water incursion.  If the surface flow of the runoff is diverted and concentrated by drains that create constant flows over the beach above the sea or river level, the beach will be eroded and ultimately form an inlet unless longshore flows deposit sediments to repair the breach.
+Once eroded, an inlet may allow tidal inflows of salt water to pollute areas inland from the beach and may also affect the quality of underground water supplies and the height of the water table.
+
+==== Deprivation of runoff ====
+Some flora naturally occurring on the beach head requires freshwater runoff from the land.  Diversion of freshwater runoff into drains may deprive these plants of their water supplies and allow sea water incursion, increasing the saltiness of the groundwater.  Species that are not able to survive in salt water may die and be replaced by mangroves or other species adapted to salty environments.
+
+==== Inappropriate beach nourishment ====
+Beach nourishment is the importing and deposition of sand or other sediments in an effort to restore a beach that has been damaged by erosion.  Beach nourishment often involves excavation of sediments from riverbeds or sand quarries.  This excavated sediment may be substantially different in size and appearance to the naturally occurring beach sand.
+In extreme cases, beach nourishment may involve placement of large pebbles or rocks in an effort to permanently restore a shoreline subject to constant erosion and loss of foreshore.  This is often required where the flow of new sediment caused by the longshore current has been disrupted by construction of harbors, breakwaters, causeways or boat ramps, creating new current flows that scour the sand from behind these structures and deprive the beach of restorative sediments. If the causes of the erosion are not addressed, beach nourishment can become a necessary and permanent feature of beach maintenance.
+During beach nourishment activities, care must be taken to place new sediments so that the new sediments compact and stabilize before aggressive wave or wind action can erode them. Material that is concentrated too far down the beach may form a temporary groyne that will encourage scouring behind it. Sediments that are too fine or too light may be eroded before they have compacted or been integrated into the established vegetation. Foreign unwashed sediments may introduce flora or fauna that are not usually found in that locality.
+Brighton Beach, on the south coast of England, is a shingle beach that has been nourished with very large pebbles in an effort to withstand the erosion of the upper area of the beach.  These large pebbles made the beach unwelcoming for pedestrians for a period of time until natural processes integrated the naturally occurring shingle into the pebble base.
+
+== Use for recreation ==
+
+=== History ===
+
+Even in Roman times, wealthy people spent their free time on the coast. They also built large villa complexes with bathing facilities (so-called maritime villas) in particularly beautiful locations. Excavations of Roman architecture can still be found today, for example on the Amalfi Coast near Naples and in Barcola in Trieste.
+The development of the beach as a popular leisure resort from the mid-19th century was the first manifestation of what is now the global tourist industry. The first seaside resorts were opened in the 18th century for the aristocracy, who began to frequent the seaside as well as the then fashionable spa towns, for recreation and health. One of the earliest such seaside resorts, was Scarborough in Yorkshire during the 1720s; it had been a fashionable spa town since a stream of acidic water was discovered running from one of the cliffs to the south of the town in the 17th century. The first rolling bathing machines were introduced by 1735.
+
+The opening of the resort in Brighton and its reception of royal patronage from King George IV, extended the seaside as a resort for health and pleasure to the much larger London market, and the beach became a centre for upper-class pleasure and frivolity. This trend was praised and artistically elevated by the new romantic ideal of the picturesque landscape; Jane Austen's unfinished novel Sanditon is an example of that. Later, Queen Victoria's long-standing patronage of the Isle of Wight and Ramsgate in Kent ensured that a seaside residence was considered as a highly fashionable possession for those wealthy enough to afford more than one home.
+
+==== Seaside resorts for the working class ====

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+---
+title: "Beach"
+chunk: 5/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+The extension of this form of leisure to the middle and working classes began with the development of the railways in the 1840s, which offered cheap fares to fast-growing resort towns. In particular, the completion of a branch line to the small seaside town of Blackpool from Poulton led to a sustained economic and demographic boom. A sudden influx of visitors, arriving by rail, led entrepreneurs to build accommodation and create new attractions, leading to more visitors and a rapid cycle of growth throughout the 1850s and 1860s.
+The growth was intensified by the practice among the Lancashire cotton mill owners of closing the factories for a week every year to service and repair machinery. These became known as wakes weeks. Each town's mills would close for a different week, allowing Blackpool to manage a steady and reliable stream of visitors over a prolonged period in the summer. A prominent feature of the resort was the promenade and the pleasure piers, where an eclectic variety of performances vied for the people's attention. In 1863, the North Pier in Blackpool was completed, rapidly becoming a centre of attraction for upper class visitors. Central Pier was completed in 1868, with a theatre and a large open-air dance floor.
+Many of the popular beach resorts were equipped with bathing machines, because even the all-covering beachwear of the period was considered immodest. By the end of the century the English coastline had over 100 large resort towns, some with populations exceeding 50,000.
+
+==== Expansion around the world ====
+
+The development of the seaside resort abroad was stimulated by the well-developed English love of the beach. The French Riviera alongside the Mediterranean had already become a popular destination for the British upper class by the end of the 18th century. In 1864, the first railway to Nice was completed, making the Riviera accessible to visitors from all over Europe. By 1874, residents of foreign enclaves in Nice, most of whom were British, numbered 25,000. The coastline became renowned for attracting the royalty of Europe, including Queen Victoria and King Edward VII.
+Continental European attitudes towards gambling and nakedness tended to be more lax than in Britain, so British and French entrepreneurs were quick to exploit the possibilities. In 1863, Charles III, Prince of Monaco, and François Blanc, a French businessman, arranged for steamships and carriages to take visitors from Nice to Monaco, where large luxury hotels, gardens and casinos were built. This area of Monaco was then renamed Monte Carlo after prince Charles III.
+Commercial sea bathing spread to the United States and parts of the British Empire by the end of the 19th century. The first public beach in the United States was Revere Beach, which opened in 1896. During that same time, Henry Flagler developed the Florida East Coast Railway, which linked the coastal sea resorts developing at St. Augustine, FL and Miami Beach, FL, to winter travelers from the northern United States and Canada on the East Coast Railway. By the early 20th century surfing was developed in Hawaii and Australia; it spread to southern California by the early 1960s. By the 1970s cheap and affordable air travel led to the growth of a truly global tourism market which benefited areas such as the Mediterranean, Australia, South Africa, and the coastal Sun Belt regions of the United States.
+
+=== Today ===
+
+Beaches can be popular on warm sunny days. In the Victorian era, many popular beach resorts were equipped with bathing machines because even the all-covering beachwear of the period was considered immodest. This social standard still prevails in many Muslim countries. At the other end of the spectrum are topfree beaches and nude beaches where clothing is optional or not allowed. In most countries social norms are significantly different on a beach in hot weather, compared to adjacent areas where similar behavior might not be tolerated and might even be prosecuted.
+In more than thirty countries in Europe, South Africa, New Zealand, Canada, Costa Rica, South America and the Caribbean, the best recreational beaches are awarded Blue Flag status, based on such criteria as water quality and safety provision. Subsequent loss of this status can have a severe effect on tourism revenues.
+Beaches are often dumping grounds for waste and litter, necessitating the use of beach cleaners and other cleanup projects. More significantly, many beaches are a discharge zone for untreated sewage in most underdeveloped countries; even in developed countries beach closure is an occasional circumstance due to sanitary sewer overflow. In these cases of marine discharge, waterborne disease from fecal pathogens and contamination of certain marine species are a frequent outcome.

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+---
+title: "Beach"
+chunk: 6/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+=== Artificial beaches ===
+Some beaches are artificial; they are either permanent or temporary (For examples, see Copenhagen, Hong Kong, Manila, Monaco, Nottingham, Paris, Rotterdam, Singapore, Tianjin, and Toronto).
+The soothing qualities of a beach and the pleasant environment offered to the beachgoer are replicated in artificial beaches, such as "beach style" pools with zero-depth entry and wave pools that recreate the natural waves pounding upon a beach. In a zero-depth entry pool, the bottom surface slopes gradually from above water down to depth. Another approach involves so-called urban beaches, a form of public park becoming common in large cities. Urban beaches attempt to mimic natural beaches with fountains that imitate surf and mask city noises, and in some cases can be used as a play park.
+Beach nourishment involves pumping sand onto beaches to improve their health. Beach nourishment is common for major beach cities around the world; however the beaches that have been nourished can still appear quite natural and often many visitors are unaware of the works undertaken to support the health of the beach. Such beaches are often not recognized by consumers as artificial. A famous example of beach nourishment came with the replenishment of Waikīkī Beach in Honolulu, Hawaii, where sand from Manhattan Beach, California was transported via ship and barge throughout most of the 20th century in order to combat Waikiki's erosion problems. The Surfrider Foundation has debated the merits of artificial reefs with members torn between their desire to support natural coastal environments and opportunities to enhance the quality of surfing waves. Similar debates surround beach nourishment and snow cannon in sensitive environments.
+
+=== Restrictions on access ===
+
+Public access to beaches is restricted in some parts of the world. For example, most beaches on the Jersey Shore are restricted to people who can purchase beach tags. Many beaches in Indonesia, both private and public, require admission fees.
+Some beaches also restrict dogs for some periods of the year.
+
+==== Private beaches ====
+
+Some jurisdictions make all beaches public by law. Some allow private ownership (for example by owners of abutting land or neighborhood associations) to the mean high tide line or mean low tide line. In some jurisdictions, the public has a general easement to use privately owned beach land for certain purposes. Signs are sometimes posted where public access ends.
+In some places, such as Florida, it is not always clear which parts of a beach are public or private.
+
+==== Public beaches ====
+The first public beach in the United States opened on 12 July 1896, in the town of Revere, Massachusetts, with over 45,000 people attending on the opening day. The beach was run bay the Metropolitan Parks Commission and the new beach had a bandstand, public bathhouses, shade pavilions, and lined by a broad boulevard that ran along the beach.
+Public access to beaches is protected by law in the U.S. state of Oregon, thanks to a 1967 state law, the Oregon Beach Bill, which guaranteed public access from the Columbia River to the California state line, "so that the public may have the free and uninterrupted use". Public access to beaches in Hawaii (other than those owned by the U.S. federal government) is also protected by state law.
+
+== Access design ==
+
+Beach access is an important consideration where substantial numbers of pedestrians or vehicles require access to the beach.  Allowing random access across delicate foredunes is seldom considered good practice as it is likely to lead to destruction of flora and consequent erosion of the fore dunes.
+A well-designed beach access should:
+
+provide a durable surface able to withstand the traffic flow;
+aesthetically complement the surrounding structures and natural landforms;
+be located in an area that is convenient for users and consistent with safe traffic flows;
+be scaled to match the traffic flow (i.e. wide and strong enough to safely carry the size and quantity of pedestrians and vehicles intended to use it);
+be maintained appropriately; and
+be signed and lit to discourage beach users from creating their own alternative crossings that may be more destructive to the beachhead.
+
+=== Concrete ramp or steps ===
+A concrete ramp should follow the natural profile of the beach to prevent it from changing the normal flow of waves, longshore currents, water and wind.  A ramp that is below the beach profile will tend to become buried and cease to provide a good surface for vehicular traffic.  A ramp or stair that protrudes above the beach profile will tend to disrupt longshore currents creating deposits in front of the ramp, and scouring behind.  Concrete ramps are the most expensive vehicular beach accesses to construct requiring use of a quick-drying concrete or a cofferdam to protect them from tidal water during the concrete curing process.  Concrete is favored where traffic flows are heavy and access is required by vehicles that are not adapted to soft sand (e.g. road registered passenger vehicles and boat trailers).  Concrete stairs are commonly favored on beaches adjacent to population centers where beach users may arrive on the beach in street shoes, or where the foreshore roadway is substantially higher than the beach head and a ramp would be too steep for safe use by pedestrians.  A composite stair ramp may incorporate a central or side stair with one or more ramps allowing pedestrians to lead buggies or small boat dollies onto the beach without the aid of a powered vehicle or winch.  Concrete ramps and steps should be maintained to prevent a buildup of moss or algae that may make their wet surfaces slippery and dangerous to pedestrians and vehicles.

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+---
+title: "Beach"
+chunk: 7/7
+source: "https://en.wikipedia.org/wiki/Beach"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:24.791061+00:00"
+instance: "kb-cron"
+---
+
+=== Corduroy (beach ladder) ===
+A corduroy road or beach ladder (or board and chain) is an array of planks (usually hardwood or treated timber) laid close together and perpendicular to the direction of traffic flow, and secured at each end by a chain or cable to form a pathway or ramp over the sand dune.  Corduroys are cheap and easy to construct and quick to deploy or relocate.  They are commonly used for pedestrian access paths and light duty vehicular access ways.  They naturally conform to the shape of the underlying beach or dune profile, and adjust well to moderate erosion, especially longshore drift.  However, they can cease to be an effective access surface if they become buried or undermined by erosion by surface runoff coming from the beach head.  If the corduroy is not wide enough for vehicles using it, the sediment on either side may be displaced creating a spoon drain that accelerates surface runoff and can quickly lead to serious erosion.  Significant erosion of the sediment beside and under the corduroy can render it completely ineffective and make it dangerous to pedestrian users who may fall between the planks.
+
+=== Fabric ramp ===
+Fabric ramps are commonly employed by the military for temporary purposes where the underlying sediment is stable and hard enough to support the weight of the traffic. A sheet of porous fabric is laid over the sand to stabilize the surface and prevent vehicles from bogging. Fabric Ramps usually cease to be useful after one tidal cycle as they are easily washed away, or buried in sediment.
+
+=== Foliage ramp ===
+A foliage ramp is formed by planting resilient species of hardy plants such as grasses over a well-formed sediment ramp.  The plants may be supported while they become established by placement of layers of mesh, netting, or coarse organic material such as vines or branches.  This type of ramp is ideally suited for intermittent use by vehicles with a low wheel loading such as dune buggies or agricultural vehicles with large tyres.  A foliage ramp should require minimal maintenance if initially formed to follow the beach profile, and not overused.
+
+=== Gravel ramp ===
+A gravel ramp is formed by excavating the underlying loose sediment and filling the excavation with layers of gravel of graduated sizes as defined by John Loudon McAdam.  The gravel is compacted to form a solid surface according to the needs of the traffic.  Gravel ramps are less expensive to construct than concrete ramps and are able to carry heavy road traffic provided the excavation is deep enough to reach solid subsoil. Gravel ramps are subject to erosion by water.  If the edges are retained with boards or walls and the profile matches the surrounding beach profile, a gravel ramp may become more stable as finer sediments are deposited by percolating water.
+
+== Longest beaches ==
+
+Amongst the world's longest beaches are:
+
+Praia do Cassino (240 kilometres [150 mi]) in Brazil;
+Eighty Mile Beach (220 kilometres [140 mi]) in north-west Australia;
+Padre Island beach (217 kilometres [135 mi]) in the Gulf of Mexico, Texas, USA. After adding an artificial inlet, the length of the Padre Island National Seashore is now 105 kilometres [65.5 mi]);
+Ninety Mile Beach, Victoria (151 kilometres [94 mi]) in Victoria, Australia;
+Cox's Bazar, Bangladesh (120 kilometres [75 mi]) in Bangladesh;
+Naikoon Provincial Park (100 kilometres [62 mi]) in the north-east of Haida Gwaii, Canada;
+90 Mile Beach (88 kilometres [55 mi]) in New Zealand;
+Playa Novillera beach (about 82 kilometres [51 mi]) in Mexico;
+Fraser Island beach (75 kilometres [47 mi]) in Queensland, Australia, located on the world's largest sand island;
+Troia-Sines Beach (65 kilometres [40 mi]) in Portugal;
+Long Beach Peninsula (45 kilometres [28 mi]), the world's longest peninsula beach, in Washington, USA.
+
+== Wildlife ==
+
+The intertidal beach is an unstable environment that exposes plants and animals to changeable and potentially harsh conditions. The number of organisms living on these beaches is a function of sand size and wave action. Beaches with smaller waves and weak baskwash tend to have finer sand, which retains more water for use by intertidal animals. Some animals burrow into the sand and feed on material deposited by the waves. Crabs, insects and shorebirds feed on these beach dwellers. The endangered piping plover and some tern species rely on beaches for nesting. Sea turtles also bury their eggs in ocean beaches. Seagrasses and other beach plants grow on undisturbed areas of the beach and dunes.
+Ocean beaches are habitats with organisms adapted to salt spray, tidal overwash, and shifting sands. Some of these organisms are found only on beaches. Examples of these beach organisms in the southeast US include plants like sea oats, sea rocket, beach elder, beach morning glory (Ipomoea pes-caprae), and beach peanut (Okenia hypogaea), and animals such as mole crabs (Hippoidea), coquina clams (Donax), ghost crabs, and white beach tiger beetles.
+
+== See also ==
+
+== Gallery ==
+
+== References ==
+
+== Works cited ==
+Andrews, Robert (2002). The Rough Guide to Britain. Rough Guides. ISBN 978-1-85828-881-9.
+
+== Further reading ==
+Bascom, W. 1980. Waves and Beaches. Anchor Press/Doubleday, Garden City, New York. 366 p.
+Schwartz, Maurice L. (1982). The Encyclopedia of Beaches and Coastal Environments: Volume 15 of Encyclopedia of earth sciences. Virginia: Hutchinson Ross Pub. Co. pp. 940. ISBN 0879332131.
+
+== External links ==
+
+Coping with beach erosion – UNESCO

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+---
+title: "Beach evolution"
+chunk: 1/5
+source: "https://en.wikipedia.org/wiki/Beach_evolution"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:26.041541+00:00"
+instance: "kb-cron"
+---
+
+Beach evolution is a natural process occurring along shorelines where sea, lake, or river water erodes the land. Beaches form as sand accumulates over centuries through recurrent processes that erode rocky and sedimentary material into sand deposits. River deltas contribute by depositing silt carried from upriver, accreting at the river's outlet to extend lake or ocean shorelines. Catastrophic events such as tsunamis, hurricanes, and storm surges accelerate beach evolution.
+
+== Accretion and erosion ==
+
+=== Sudden and rapid processes ===
+
+==== Tsunamis and hurricane-driven storm surges ====
+
+Tsunamis can cause significant erosion and sediment displacement. They can strip away years of accumulated sand from beaches and devastate coastal vegetation. These powerful waves can flood inland areas far beyond the typical high-tide mark. Additionally, the swift currents associated with the inundating tsunami can demolish homes and other coastal structures.
+A storm surge is an onshore gush of water associated with a low pressure weather system. Storm surges can cause beach accretion and erosion. Historically notable storm surges occurred during the North Sea Flood of 1953, Hurricane Katrina, and the 1970 Bhola cyclone.
+
+==== Volcanism and earthquakes related sea-level changes ====
+Both geological events and the climate can change (progressively or suddenly) the relative height of the Earth's surface to the sea-level. These events or processes continuously change coastlines.
+
+Volcanic activity can create new islands. For example, Surtsey Island in Iceland which has a diameter of 800 meters (2,600 ft), was created between November 1963 and June 1967. The island emerged from undersea vents that are part of the Vestmannaeyjar submarine volcanic system. Although the island has since partially eroded, but it is expected to last another 100 years.
+Some earthquakes can create sudden variations of relative ground level and change the coastline dramatically. Structurally controlled coasts include the San Andreas Fault zone in California and the seismic Mediterranean belt (from Gibraltar to Greece).
+The Bay of Pozzuoli, in Pozzuoli, Italy experienced hundreds of tremors between August 1982 and December 1984. The tremors, which reached a peak on October 4, 1983, damaged 8,000 buildings in the city center and raised the sea bottom by almost 2 meters (6.6 ft). This rendered the Bay of Pozzuoli too shallow for large craft and required the reconstruction of the harbor with new quays. The photo at the upper right shows the harbor before the uplift while the one on the bottom right shows the new quay.
+
+=== Gradual processes ===
+The gradual evolution of beaches often comes from the interaction of longshore drift, a wave-driven process by which sediments move along a beach shore, and other sources of erosion or accretion, such as nearby rivers.
+
+==== Deltas ====
+Deltas are nourished by alluvial systems and accumulate sand and silt, growing where the sediment flux from land is large enough to avoid complete removal by coastal currents, tides, or waves.
+Most modern deltas are formed during the last five thousand years, after the present sea-level high stand was attained. However, not all sediment remains permanently in place: in the short term (decades to centuries), exceptional river floods, storms or other energetic events may remove significant portions of delta sediment or change its lobe distribution (pattern in which sediments are deposited across Delta, forming distinct, lobe shaped structures) and, on longer geological time scales, sea-level fluctuations lead to the destruction of deltaic features.
+
+==== Subsidence and uplift related sea-level changes ====
+Subsidence is the motion of the Earth's surface downward relative to the sea level due to internal geodynamic causes, It can occur naturally or due to human activities. The opposite of subsidence is uplift, which increases elevation.
+
+Venice is probably the best-known example of a subsiding location. Built suspended over a coastal lagoon, it experiences periodic flooding when extreme high tides or surges arrive; St Mark's Square is built only 55 centimeters above sea level. This phenomenon is caused by the compaction of young sediments in the Po River delta area, magnified by subsurface water and gas exploitation. Man-made works to solve this progressive sinking have been unsuccessful.
+Mälaren, the third-largest lake in Sweden, is an example of deglacial uplift. It was once a bay on which seagoing vessels were once able to sail far into the country's interior, but it ultimately became a lake. Its uplift was caused by deglaciation: the removal of the weight of ice-age glaciers caused rapid uplift of the depressed land. For 2,000 years as the ice was unloaded, uplift proceeded at about 7.5 centimeters (3.0 in)/year. Once deglaciation was complete, uplift slowed to about 2.5 centimeters (0.98 in) annually, and it decreased exponentially after that. Today, annual uplift rates are 1 centimeter (0.39 in) or less, and studies suggest that rebound will continue for about another 10,000 years. The total uplift from the end of deglaciation may be up to 400 meters (1,300 ft).
+
+== Beach management ==
+
+Integrated coastal zone management minimizes the negative human impacts on coasts, enhances coastal defense, mitigates the risk associated with the sea level rise and other natural hazards.
+The beach erosion is a type of bioerosion which alters the coastal geography through beach morphodynamics. There are numerous incidents of modern recession of beaches, mainly due to the longshore drift and coastal development hazards related to human activities.
+Solutions range from "do nothing" to "Move beach seaward" approach which uses the elements of hard and soft engineering. The interventionist methods, such as "Move beach seaward", combine the hard engineering methods such as constructing structures (accropodes) with the soft engineering methods such as sand dune stabilization. These intervention are aimed at prevention of beach erosion caused by longshore drift and coastal development hazards, as well as facilitation of beach evolution and expansion.
+
+=== Coastal planning approaches ===
+
+Five generic planning approaches involved in coastal defense are:

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+---
+title: "Beach evolution"
+chunk: 2/5
+source: "https://en.wikipedia.org/wiki/Beach_evolution"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:26.041541+00:00"
+instance: "kb-cron"
+---
+
+Abandonment of shore: do nothing, let the natural process takeover.
+Managed retreat, also called realignment.
+Hold the shoreline: by using shoreline hardening techniques to create permanent concrete and rock constructions such as groynes.
+Move beach seaward: by using hard and soft intervention techniques usually in areas of high economic significance.
+Limited intervention: usually in areas of low economic significance, often includes the succession of haloseres, including salt marshes and sand dunes.
+
+=== Coastal engineering ===
+
+Coastal engineering techniques can be classified into two categories: hard engineering methods and soft engineering methods
+
+==== Hard engineering methods ====
+Hard engineering methods are also called "Structural methods". "Move towards the sea" beach accretion can be facilitated by the four main type of hard engineering structures, namely seawall, revetment, groyne or breakwater. Most commonly used hard structures are seawall and series of "headland groyne" (breakwater connected to the shore with groyne).
+
+===== Main types of structures =====
+Four main types of structures or accropodes are seawalls, groynes, breakwater and revetments. Headland groynes are a combination of breakwater and groyne.
+
+====== Seawalls ======
+Seawalls re-direct most of the incident energy in the form of sloping revetments, resulting in low reflected waves and much reduced turbulence. Designs use porous designs of rock or concrete objects such as Tetrapods or Xblocs with flights of steps for beach access. Seawall at Cronulla beach, NSW, for example, uses concrete wall. Submerged seawalls or structures are constructed to create the underwater reefs to slow down wave energy and beach erosion.
+
+====== Groynes and Headland groyne ======
+Groynes are the walls perpendicular to the coastline. Groynes are generally placed in series and the areas between groups of groynes are called groyne fields. To directs the sand towards the shore targeted for sand accumulation, a shorter groyne turned slightly towards downdrift side of the beach is deployed at updrift end of the beach, a longer groyne at the downdrift end of the beach is deployed, a series of groyne are deployed between the two ends. Groynes are often made of gabion, greenharts, concrete, rock or wood. Material builds up on the downdrift side, where littoral drift is predominantly in one direction, creating a wider and a more plentiful beach. Groynes are cost-effective, require little maintenance and are one of the most common defences.
+
+Headland groyne or Bulkhead breakwater
+When groyne is built to attach a breakwater to shore, the resulting T-structure is called "headland breakwater", "headland groyne", "bulkhead groyne" or "bulkhead breakwater". Use of groynes and headland groyne, accumulates the sand across the beach but it tend to deplete the sand faster from the downdrift end of the beach. This can be mitigated and sand could be accumulated at the downdrift end of the beach also. This is achieved by having a longer "groyne" or "headland groyne" at the end of downdrift side of the beach. To enhance the sand accumulation, this "headland groyne" could have another series of smaller "headland groyne" jutting out of it pointing towards updrift end of the beach in a way that the smaller "headland groyne" are parallel to the shore and perpendicular to main "headland groyne". This will facilitate gradual natural creation of ayre (sand or gravel filled beach). If there is a near shore island near the downdrift end of the beach and "headland groyne", then this could be turned into a cuspate foreland headland with the use of the gradual natural creation of ayre (gravel filled beach). Main "headland groyne" at the end of downdrift could be further stabilized by a hard engineered detention basin and grassy mangrove salt marsh. Salt marsh could be created with the use of soft engineering approach, such as lose stone sills, while leaving a whole in the sill for a seawater channel. Seawater channel could be a cemented open channel or a pipe buried under the beach. This marsh could be designed to taper into a hard engineered sandy beach. Having inland saltwater marsh between the beach and mainland will lower the cost by eliminating the need for filling up the marshy area with the sand, and the mangroves and grasses in the marsh will facilitate gradual built up of sediments.
+
+====== Breakwater ======
+Breakwater, also called "offshore breakwater", are offshore structure constructed parallel to the shore to alter wave direction and tide energy. The waves break further offshore and therefore lose erosive power. This leads to formation of wider beaches, which further absorb wave energy. A series of breakwaters is often deployed across the beach shore.
+
+====== Revetment ======
+Revetments are slanted or upright blockades, built parallel to the coast, usually towards the back of the beach to protect the area beyond. The most basic revetments consist of timber slants with a possible rock infill. Waves break against the revetments, which dissipate and absorb the energy. The shoreline is protected by the beach material held behind the barriers, as the revetments trap some of the material. Unless other methods are used in combination, surf progressively erodes and destroys the revetment which requires ongoing maintenance.
+
+===== Other types of structures =====
+
+====== Riprap / Rock armour ======
+Rock armour, also called riprap, is basement placed at the sea edge using local material. This could be the protruding foot of a seawall or revetment to reduce maintenance of those. Longshore drift is not hindered.
+
+====== Cliff stabilization ======
+Cliff stabilization can be accomplished through drainage of excess rainwater of through terracing, planting and wiring to hold cliffs in place.
+
+====== Floodgates ======
+Floodgates prevent damage from storm surges or any other type of natural disaster that could harm the area they protect. They are habitually open and allow free passage, but close under threat of a storm surge. The Thames Barrier is an example of such a structure.
+
+===== Construction elements =====
+These construction elements can be incorporated in any of the above structures, either as core element or as a supplementary element to enhance to reduce the cost and maintenance of main structural elements.

data/en.wikipedia.org/wiki/Beach_evolution-2.md

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+---
+title: "Beach evolution"
+chunk: 3/5
+source: "https://en.wikipedia.org/wiki/Beach_evolution"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:26.041541+00:00"
+instance: "kb-cron"
+---
+
+====== Concrete objects ======
+These are complex reinforced concrete objects, such as A-jack, Akmon, Dolos, Honeycomb sea wall (Seabees), KOLOS, Tetrapod and Xbloc. Simple concrete blocks have been replaced by these complex concrete objects because these objects are more resistant to wave action and require less concrete to produce a superior result. These could be used to build seawalls, groynes, breakwaters, and other structures including residential buildings. Tetrapods used along Marine Drive, Mumbai are an example of complex concrete objects.
+
+====== Gabions ======
+Gabions are constructed by wiring boulders and rocks into mesh cages and placed in front of areas vulnerable to erosion, sometimes at cliffs edges or at right angles to the beach. When the ocean lands on the gabion, the water drains through leaving sediment, while the structure absorbs a moderate amount of wave energy. Gabions need to be securely tied to protect the structure. They can be used to build seawalls, groynes, breakwaters, revetments, buildings, underwater reefs, etc.,
+
+==== Soft engineering methods ====
+
+Soft engineering uses a "soft" (non-permanent) structure by creating a larger sand reservoir, pushing the shoreline seaward. It gained popularity because it preserved beach resources and avoided the negative effects of hard structures.
+
+===== Managed retreat =====
+Managed retreat means the shoreline is left to erode, while relocating buildings and infrastructure further inland.
+
+===== Beach evolution =====
+Beach evolution, also called "beach replenishment" or "beach nourishment", it involves importing sand from elsewhere and adding it to the existing beach. The imported sand should be of a similar quality to the existing beach material so it can meld with the natural local processes and without adverse effects. Without the groynes or scheme requires repeated applications on an annual or multi-year cycle. Beach nourishment can be used in combination with seaward curving half-moon shaped "headland breakwater" structure, this combining the benefits of breakwater and groyne structures.
+
+===== Sand dune stabilization =====
+Sand dune stabilization protects beaches by catching windblown sand, increasing natural beach formation. Fences can allow sand traps to create blowouts and increase windblown sand capture. Plants such as Ammophila (Marram grass) can bind the sediment.
+
+===== Beach drainage =====
+The beach face dewatering lowers the water table locally beneath the beach face. This causes accretion of sand above the drainage system.
+
+=== Cost considerations ===
+The costs of installation, operation and maintenance vary due to:
+
+system length (non-linear cost elements)
+flow rates (sand permeability, power costs)
+soil conditions (presence of rock or impermeable strata)
+discharge arrangement /filtered seawater utilization
+drainage design, materials selection & installation methods
+geographical considerations (location logistics)
+regional economic considerations (local capabilities /costs, availability of local material and native skilled workforce)
+study requirements /consent process.
+
+=== An illustrative example ===

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+---
+title: "Beach evolution"
+chunk: 4/5
+source: "https://en.wikipedia.org/wiki/Beach_evolution"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:26.041541+00:00"
+instance: "kb-cron"
+---
+
+This Integrated coastal zone management example is based on the "move beach seaward" general planning approach which involves both hard and soft engineering methods. This scenario minimizes the maintenance effort and cost by making optimal use of the coastal geography by incorporating natural coastal geographical features in the engineering design. The cost is kept low by the use of easily available free or cost-effective local material, use of which is already known to or easily acquired by the local workforce. This solution entails beach nourishment (creating recreational area by filling with sand), and further beach expansion and prevention of beach erosion caused by longshore drift and coastal development hazards. The design makes use of a shorter groyne slightly inclined toward the beach in the same direction as downdrift, with a series of "headland groyne" perpendicular to the shore, and a longer "headland groyne" at the end of downdrift side of the beach with smaller "headland groyne" perpendicular to it facing the updrift end of the beach.
+This example of tropical setting, part of the sea could be reclaimed by building a seawall with revetment (slope) fortified with armament of honeycomb seebee made of concrete with hexagonal holes, parts of seawall could be made of gabion. Seawall will sit over gravel or rock. Seawall could be a mix of vertical structures in the areas where more space is needed and tapering revetments (slope) as aesthetic landscaping feature. Revetments could be made of locally available material. Different parts of revetment could have different material and design, such as gabion (welded wire mesh filled with stone, gravel and wood) and honeycomb seebee (made of concrete with hexagonal holes). Honeycomb seebee or gabion could be used in the downdrift areas, though wood groyne would be the cheapest option such as used at Mundesley. Other areas of seawall and revetment could be a mix of cemented low walls, gabion, riprap made of gravel or sand bags. Parts of seawall and revetment could be left exposed especially those made of decorative gabion, and others parts could be covered with low or mid level native plants. Seawall will sit over gravel or rock base which could be wider than the seawall so that it also acts as the riprap armament.
+Reclaimed area could be filled with the sand and stabilized by aesthetic landscaping by growing native trees and plants. A dense layer of native tropical trees could be planted at the mainland side of the reclaimed land with due consideration to the height of the trees that they do not block the view of any construction such as resort or beach house. Reclaimed area would enhance the economical value by creating a sand filled safe recreation area which might house sunbathing areas and inland freshwater or seawater wading pool or lagoon surrounded by bars, restaurants, water sports, etc. Restaurants could have retractable-canopied areas set closer to the seawall greenified with tapering layers of evergreen native tropical plants. Bars could be open air, portable or canopied (thatched roof nipa hut and trellis of native material, pergola or beach parasol) bars with pool and beach seating. Seating could be relaxing-and-sprawling reclined futon type, sunken sand pits, sand filled bean bags on the beach, locally made designer stools/chairs and tables made of native eco-friendly natural material such as bamboo, aged rustic driftwood and abundant low weathering native wood.
+
+== Status of beaches ==
+
+=== Historical accretion of beaches ===
+
+In the Mediterranean Sea, deltas have been continuously growing for the last several thousand years. Six to seven thousand years ago, the sea level stabilized, and continuous river systems, ephemeral torrents, and other factors began this steady accretion. Since intense human use of coastal areas is a relatively recent phenomenon (except in the Nile delta), beach contours were primarily shaped by natural forces until the last centuries.
+In Barcelona, for example, the accretion of the coast was a natural process until the late Middle Ages, when harbor-building increased the rate of accretion.
+The port of Ephesus, one of the great cities of the Ionian Greeks in Asia Minor, was filled with sediment due to accretion from a nearby river; it is now 5 kilometers (3.1 mi) from the sea. Likewise, Ostia, the once-important port near ancient Rome, is now several kilometres inland, the coastline having moved slowly seaward.
+Bruges became a port during the early Middle Ages and was accessible by sea until around 1050. At that time, however, the natural link between Bruges and the sea silted up. In 1134, a storm flood opened a deep channel, the Zwin, linking the city to the sea until the fifteenth century via a canal from the Zwin to Bruges. Bruges had to use a number of outports, such as Damme and Sluis, for this purpose. In 1907, a new seaport was inaugurated in Zeebrugge.
+
+=== Modern beach recession ===
+
+At the present time, important segments of low coasts are in recession, losing sand and reducing beach dimensions. This loss can occur very rapidly. There are various reasons for beach recession, some more natural than others (degree of anthropization). Examples of this are occurring at Sète, in California, in Poland, in Aveiro (Portugal), and in the Netherlands and elsewhere along the North Sea. In Europe, coastal erosion is widespread (at least 70%) and distributed very irregularly.

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+---
+title: "Beach evolution"
+chunk: 5/5
+source: "https://en.wikipedia.org/wiki/Beach_evolution"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:26.041541+00:00"
+instance: "kb-cron"
+---
+
+==== California beaches ====
+California's beaches and other shoreline features change according to the availability of beach sand, the wave and current energy impinging on the coast, and other physical processes that affect the movement of sand. A constant supply of sand is necessary for beaches to form and be maintained along this shoreline. Many human activities, including dam construction and river channelization, have reduced the supply of sand that reaches the ocean. This, in turn, has prevented beaches from being replenished and has thus created greater vulnerability for shorelines that have always been subject to varying levels of erosion. There are few practical solutions to improving sand supply from inland sources, so management of shoreline erosion will likely continue to focus at the land/sea interface along the California coastline.
+Construction of breakwaters, jetties, or groyne fields to protect harbor entrances, maintain beaches, or protect coastal structures have both helped and harmed the movement of sand along the shoreline. Protective armoring formations trap sand and allow beaches to expand up-coast from the device, but can interrupt the flow of sand to beaches located down-coast.
+
+==== France ====
+
+===== Atlantic coast =====
+
+Some of the coastal defence bunkers of the Atlantic Wall, built by the German soldiers during the Second World War at the top of the dunes were underwater 2/3 of the time 65 years after the war. It shows 200 meters of recession of the beach in 65 years.
+
+===== Sète =====
+The coast recession near Sète is related with coastal drift sand supply interruption due to growth of the Rhone delta, which (like most deltas) is becoming independent of the rest of the coast. The present lido shoreline is 210 meters away from the Roman lido.
+
+==== Netherlands ====
+
+The Dutch coast consists of sandy, multi-barred beaches and can be characterised as a wave-dominated coast. Approximately 290 km of the coast consists of dunes and 60 km is protected by structures such as dikes and dams. With the melting of the ice at the end of the last ice age, the coastline shifted eastward until about 5000 years ago the present position of the Dutch coastline was reached. As the sea level rise stagnated, the sand supply decreased and the formation of the beach ridges stopped, after which when the sea broke through the lines of dunes during storms, men started to defend the land by building primitive dikes and walls. The dunes, together with the beach and the shoreline, offer a natural, sandy defence to the sea. About 30% of the Netherlands lies below sea level.
+
+Over the last 30 years, approximately 1 million m3 sand per year has been lost from the Dutch coast to deep water. In most northern coastal sections, erosion occurs in deep water and also in the nearshore zone. In most southern sections, sedimentation occurs in the nearshore zone and erosion in deep water. Structural erosion is due to sea-level rise relative to the land and, in some spots, it is caused by harbour dams. The Dutch coast looked at as a single unit shows erosive behaviour. Approximately 12 million m3 of sand is transferred annually from the North Sea to the Wadden Sea as a result of relative rising sea level and coastal erosion.
+
+==== Poland ====
+During the last glaciation, the Baltic Polish area was covered in ice and associated morainal sediments. Deglaciation left a substantial amount of unconsolidated sediment. Currently, these unconsolidated sediments are strongly eroded and reworked by the sea.
+
+==== Portugal ====
+The North Portuguese coast and its beaches were fed by large Iberian rivers. The massive building of dams in the Douro River basin has cut the sediment supply to the Aveiro coast, resulting in its recession. Hard protective works have been done all along.
+
+== See also ==
+
+== References ==
+
+== External links ==
+The Deltas-Global Change Program (DCP) 
+Mediterranean Prodelta Systems
+EUROSION project web site

data/en.wikipedia.org/wiki/Beachrock-0.md

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+---
+title: "Beachrock"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Beachrock"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:27.242877+00:00"
+instance: "kb-cron"
+---
+
+Beachrock is a friable to well-cemented sedimentary rock that consists of a variable mixture of  gravel-, sand-, and silt-sized sediment that is cemented with carbonate minerals and has formed along a shoreline. Depending on location, the sediment that is cemented to form beachrock can consist of a variable mixture of shells, coral fragments, rock fragments of different types, and other materials. It can also contain scattered artifacts, pieces of wood, and coconuts. Beachrock typically forms within the intertidal zone within tropical or semitropical regions. However, Quaternary beachrock is also found as far north and south as 60° latitude.
+
+
+== Overview ==
+Beachrock units form under a thin cover of sediment and generally overlie unconsolidated sand. They typically consist of multiple units, representing multiple episodes of cementation and exposure. The mineralogy of beachrocks is mainly high-magnesium calcite or aragonite. The main processes involved in the cementation are : supersaturation with CaCO3 through direct evaporation of seawater, groundwater CO2 degassing in the vadose zone, mixing of marine and meteoric water fluxes and precipitation of micritic calcium carbonate as a byproduct of microbiological activity.
+On retreating coasts, outcrops of beachrock may be evident offshore where they may act as a barrier against coastal erosion. Beachrock presence can also induce sediment deficiency in a beach and out-synch its wave regime. Because beachrock is lithified within the intertidal zone and because it commonly forms in a few years, its potential as an indicator of past sea level is important.
+
+
+== Cementation and position of beachrock ==
+Beachrocks are located along the coastline in a parallel term and they are usually a few meters offshore. They are generally separated in several levels which may correspond to different generations of beachrock cementation. Thus, the older zones are located in the outer part of the formation when the younger ones are on the side of the beach, possibly under the unconsolidated sand. They also seem to have a general inclination to the sea (50–150). There are several appearances of beachrock formations which are characterized by multiple cracks and gaps. The result from this fact is an interruptible formation of separated blocks of beachrock, which may be of the same formation.
+The length of beachrocks varies from meters to kilometers, its width can reach up to 300 meters and its height starts from 30 cm and reaches 3 meters.
+Following the process of coastal erosion, beachrock formation may be uncovered. Coastal erosion may be the result of sea level rise or deficit in sedimentary equilibrium. One way or another, unconsolidated sand that covers the beachrock draws away and the formation is revealed. If the process of cementation continues, new beachrock would be formed in a new position in the intertidal zone. Successive phases of sea level change may result in sequential zones of beachrock.
+
+
+== See also ==
+Bimini Road
+Coquina
+
+
+== References ==

data/en.wikipedia.org/wiki/Benthic_zone-0.md

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+---
+title: "Benthic zone"
+chunk: 1/5
+source: "https://en.wikipedia.org/wiki/Benthic_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:28.462475+00:00"
+instance: "kb-cron"
+---
+
+The benthic zone, from Ancient Greek  βένθος (bénthos) 'the depths of the ocean', is the ecological region at the lowest level of a body of water, such as a stream, river, lake, or ocean, including the sediment surface and some sub-surface layers.
+Organisms living in this zone are called benthos, or more informally bottom dwellers. They include microorganisms such as bacteria and fungi, as well as larger invertebrates such as crustaceans and polychaetes. Benthos generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud.
+
+== Physical description ==
+
+=== Oceans ===
+The benthic region of the ocean begins at the shore line (intertidal or littoral zone) and extends downward along the surface of the continental shelf out to sea. Thus, the region incorporates a great variety of physical conditions differing in depth, light penetration and pressure. The benthic zone includes all areas of bottom that are below the water.
+The continental shelf is a benthic region of a tectonic plate that extends away from the shoreline of a land mass.  At the continental shelf edge, usually about 200 metres (660 ft) deep, the gradient greatly increases and is known as the continental slope. The continental slope drops down to the deep sea floor. The generally flat part of the deep-sea floor is called the abyssal plain and is usually about 4,000 metres (13,000 ft) deep. The ocean floor is not all flat but has submarine ridges, seamounts and deep ocean trenches known as the hadal zone. For comparison, the pelagic zone is the ecological region above the benthos, comprising the water column up to the surface. The  benthos of the deep ocean includes the bottom levels of the oceanic abyssal zone.
+The deeper areas of the oceans beyond the penetration of daylight are the aphotic zone. Generally, this region is inhabited by life forms that tolerate cool temperatures and low oxygen levels, depending on the depth of the water.
+
+=== Lakes ===
+As with oceans, the benthic zone is the floor of the lake, which may be covered by accumulated sunken organic matter and mineral sediments, and the organisms that live in and on it. The littoral zone is the zone bordering the shore; light penetrates easily and aquatic plants thrive.  The pelagic zone is the water between the surface and the bottom. the photic zone is the water column down to the depth to which no light penetrates. This depth varies depending on clarity of the water.
+
+== Benthos ==

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+---
+title: "Benthic zone"
+chunk: 2/5
+source: "https://en.wikipedia.org/wiki/Benthic_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:28.462475+00:00"
+instance: "kb-cron"
+---
+
+Benthos is the community of organisms that live in the benthic zone, that is, on, in, or near the bottom of a stream, river, lake, or ocean. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. 
+The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος 'depth of the ocean'. Additionally to oceans, benthos is also used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as streams, rivers, and lakes. There is also a redundant, occasionally used synonym, benthon. Benthos is also referred to more loosely and informally as bottom dwellers or bottom feeders. 
+Light is an important energy source for shallow benthic systems. However, because light is absorbed before it can reach deep ocean water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores.
+Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column. The pressure difference can be significant (approximately one atmosphere for every 10 metres of water depth).
+Compared to the relatively featureless pelagic zone, the benthic zone offers physically diverse habitats. There is a huge range in how much light and warmth is available, and in the depth of water or extent of intertidal immersion. The seafloor varies widely in the types of sediment it offers. Burrowing animals can find protection and food in soft, loose sediments such as mud, clay and sand. Sessile species such as oysters and barnacles can attach themselves securely to hard, rocky substrates. As adults they can remain at the same site, shaping depressions and crevices where mobile animals find refuge. This greater diversity in benthic habitats has resulted in a higher diversity of benthic species. The number of benthic animal species exceeds one million. This far exceeds the number of pelagic animal species (about 5000 larger zooplankton species, 22,000 pelagic fish species and 110 marine mammal species).
+Benthos are the organisms that live in the benthic zone, and are different from those elsewhere in the water column; even within the benthic zone variations in such factors as substrate, light penetration, temperature and salinity give rise to distinct differences, delineated vertically, in the groups of organisms supported. Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column: the pressure difference can be very significant (approximately one atmosphere for each 10 meters of water depth).  Many have adapted to live on the substrate (bottom) or within the upper layers of the bottom. In their habitats they can be considered as dominant creatures, but they are often a source of prey for Carcharhinidae such as the lemon shark.
+Because light does not penetrate very deep into ocean-water, the energy source for the benthic ecosystem is often marine snow. Marine snow is organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores. Some microorganisms use chemosynthesis to produce biomass.
+Benthic organisms can be divided into two categories based on whether they make their home on the ocean floor or a few centimeters into the ocean floor. Those living on the surface of the ocean floor are known as epifauna. Those who live burrowed into the ocean floor are known as infauna. Extremophiles, including piezophiles, which thrive in high pressures, may also live there.
+
+=== By taxon ===
+
+=== By size ===
+
+==== Macrobenthos ====
+
+Macrobenthos, prefix from Ancient Greek  makrós 'long', comprises the larger, visible to the naked eye, benthic organisms greater than about 1 mm in size. In shallow waters, seagrass meadows, coral reefs and kelp forests provide particularly rich habitats for macrobenthos. Some examples are polychaete worms, bivalves, echinoderms, sea anemones, corals, sponges, sea squirts, turbellarians and larger crustaceans such as crabs, lobsters and cumaceans.
+
+==== Meiobenthos ====
+
+Meiobenthos, prefix from Ancient Greek  meîon 'less', comprises tiny benthic organisms that are less than about 1 mm but greater than about 0.1 mm in size. Some examples are nematodes, foraminiferans, tardigrades, gastrotriches and smaller crustaceans such as copepods and ostracodes.
+
+==== Microbenthos ====
+
+Microbenthos, prefix from the Greek mikrós 'small', comprises microscopic benthic organisms that are less than about 0.1 mm in size. Some examples are bacteria, diatoms, ciliates, amoeba, flagellates.
+
+Marine microbenthos are microorganisms that live in the benthic zone of the ocean – that is, near or on the seafloor, or within or on surface seafloor sediments.  Microbenthos are found everywhere on or about the seafloor of continental shelves, as well as in deeper waters, with greater diversity in or on seafloor sediments. In photic zones benthic diatoms dominate as photosynthetic organisms. In intertidal zones changing tides strongly control opportunities for microbenthos.

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+---
+title: "Benthic zone"
+chunk: 3/5
+source: "https://en.wikipedia.org/wiki/Benthic_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:28.462475+00:00"
+instance: "kb-cron"
+---
+
+Both foraminifera and diatoms have planktonic and benthic forms, that is, they can drift in the water column or live on sediment at the bottom of the ocean. Regardless of form, their shells sink to the seafloor after they die. These shells are widely used as climate proxies. The chemical composition of the shells are a consequence of the chemical composition of the ocean at the time the shells were formed. Past water temperatures can be also be inferred from the ratios of stable oxygen isotopes in the shells, since lighter isotopes evaporate more readily in warmer water leaving the heavier isotopes in the shells. Information about past climates can be inferred further from the abundance of forams and diatoms, since they tend to be more abundant in warm water.The sudden extinction event which killed the dinosaurs 66 million years ago also rendered extinct three-quarters of all other animal and plant species. However, deep-sea benthic forams flourished in the aftermath. In 2020 it was reported that researchers have examined the chemical composition of thousands of samples of these benthic forams and used their findings to build the most detailed climate record of Earth ever.
+Some endoliths have extremely long lives. In 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old, with a generation time of 10,000 years. These are slowly metabolizing and not in a dormant state. Some Actinomycetota found in Siberia are estimated to be half a million years old.
+
+=== By trophic level ===
+
+==== Zoobenthos ====
+Zoobenthos, prefix from Ancient Greek  zôion 'animal', animals belonging to the benthos. Examples include polychaete worms, starfish and anemones.
+
+==== Phytobenthos ====
+Phytobenthos, prefix from Ancient Greek  phutón 'plant', plants belonging to the benthos, mainly benthic diatoms and macroalgae (seaweed).
+
+=== By location ===
+
+==== Endobenthos ====
+Endobenthos (or endobenthic), prefix from Ancient Greek  éndon 'inner, internal', lives buried, or burrowing in the sediment, often in the oxygenated top layer, e.g., a sea pen or a sand dollar.
+
+==== Epibenthos ====
+Epibenthos (or epibenthic), prefix from Ancient Greek  epí 'on top of', lives on top of the sediments, e.g., sea cucumber or a sea snail.
+
+==== Hyperbenthos ====
+Hyperbenthos (or hyperbenthic), prefix from Ancient Greek  hupér 'over', lives just above the sediment, e.g., a rock cod.
+
+=== By habitat ===
+
+Modern seafloor mapping technologies have revealed linkages between seafloor geomorphology and benthic habitats, in which suites of benthic communities are associated with specific geomorphic settings. Examples include cold-water coral communities associated with seamounts and submarine canyons, kelp forests associated with inner shelf rocky reefs and rockfish associated with rocky escarpments on continental slopes. In oceanic environments,  habitats can also be zoned by depth. From the shallowest to the deepest are: the epipelagic (less than 200 meters), the mesopelagic (200–1,000 meters), the bathyal (1,000–4,000 meters), the abyssal (4,000–6,000 meters) and the deepest, the hadal (below 6,000 meters).
+
+Human impacts have occurred at all ocean depths, but are most significant on shallow continental shelf and slope habitats.  Many benthic organisms have retained their historic evolutionary characteristics. Some organisms are significantly larger than their relatives living in shallower zones, largely because of higher oxygen concentration in deep water.
+It is not easy to map or observe these organisms and their habitats, and most modern observations are made using remotely operated underwater vehicles (ROVs), and rarely crewed submersibles.
+Tide pools provide somewhat demanding benthic homes for organisms such as sea stars, mussels and clams. Inhabitants deal with a frequently changing environment: fluctuations in water temperature, salinity, and oxygen content. Hazards include waves, strong currents, exposure to midday sun and predators. Waves can dislodge mussels and draw them out to sea. Gulls pick up and drop sea urchins to break them open. Sea stars prey on mussels and are eaten by gulls themselves. Black bears are known to sometimes feast on intertidal creatures at low tide. Although tide pool organisms must avoid getting washed away into the ocean, drying up in the sun, or being eaten, they depend on the tide pool's constant changes for food. Tide pools contain complex food webs that can vary based on the climate.
+
+== Ecological roles ==

data/en.wikipedia.org/wiki/Benthic_zone-3.md

@@ -0,0 +1,26 @@
+---
+title: "Benthic zone"
+chunk: 4/5
+source: "https://en.wikipedia.org/wiki/Benthic_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:28.462475+00:00"
+instance: "kb-cron"
+---
+
+=== Nutrient flux ===
+Sources of food for benthic communities can derive from the water column above these habitats in the form of aggregations of detritus, inorganic matter, and living organisms. These aggregations are commonly referred to as marine snow, and are important for the deposition of organic matter, and bacterial communities.  The amount of material sinking to the ocean floor can average 307,000 aggregates per m2 per day. This amount will vary on the depth of the benthos, and the degree of benthic-pelagic coupling. The benthos in a shallow region will have more available food than the benthos in the deep sea. Because of their reliance on it, microbes may become spatially dependent on detritus in the benthic zone. The microbes found in the benthic zone, specifically dinoflagellates and foraminifera, colonize quite rapidly on detritus matter while forming a symbiotic relationship with each other. In the deep sea, which covers 90–95% of the ocean floor, 90% of the total biomass is made up of prokaryotes. To release all the nutrients locked inside these microbes to the environment, viruses are important in making it available to other organisms.
+The main food sources for the benthos are phytoplankton and organic detrital matter. In coastal locations, organic run off from land provides an additional food source. Meiofauna and bacteria consume and recycle organic matter in the sediments, playing an important role in returning nitrate and phosphate to the pelagic.
+The depth of water, temperature and salinity, and type of local substrate all affect what benthos is present. In coastal waters and other places where light reaches the bottom, benthic photosynthesizing diatoms can proliferate. Filter feeders, such as sponges and bivalves, dominate hard, sandy bottoms. Deposit feeders, such as polychaetes, populate softer bottoms. Fish, such as dragonets, as well as sea stars, snails, cephalopods, and crustaceans are important predators and scavengers.
+Benthic organisms, such as sea stars, oysters, clams, sea cucumbers, brittle stars and sea anemones, play an important role as a food source for fish, such as the California sheephead, and humans.
+
+=== Carbon processing ===
+
+Organic matter produced in the sunlit layer of the ocean and delivered to the sediments is either consumed by organisms or buried. The organic matter consumed by organisms is used to synthesize biomass (i.e. growth) converted to carbon dioxide through respiration, or returned to the sediment as faeces. This cycle can occur many times before either all organic matter is used up or eventually buried. This process is known as the biological pump.
+In the long-term or at steady-state, i.e., the biomass of benthic organisms does not change, the benthic community can be considered a black box diverting organic matter into either metabolites or the geosphere (burial). The macrobenthos also indirectly impacts carbon cycling on the seafloor through bioturbation.
+
+=== As bioindicators ===
+Benthic macro-invertebrates play a critical role in aquatic ecosystems. These organisms can be used to indicate the presence, concentration, and effect of water pollutants in the aquatic environment. Some water contaminants—such as nutrients, chemicals from surface runoff, and metals—settle in the sediment of river beds, where many benthos reside. Benthos are highly sensitive to contamination, so their close proximity to high pollutant concentrations make these organisms ideal for studying water contamination.
+Benthos can be used as bioindicators of water pollution through ecological population assessments or through analyzing biomarkers. In ecological population assessments, a relative value of water pollution can be detected. Observing the number and diversity of macro-invertebrates in a waterbody can indicate the pollution level. In highly contaminated waters, a reduced number of organisms and only pollution-tolerant species will be found. In biomarker assessments, quantitative data can be collected on the amount of and direct effect of specific pollutants in a waterbody. The biochemical response of macro-invertebrates' internal tissues can be studied extensively in the laboratory. The concentration of a chemical can cause many changes, including changing feeding behaviors, inflammation, and genetic damage, effects that can be detected outside of the stream environment. Biomarker analysis is important for mitigating the negative impacts of water pollution because it can detect water pollution before it has a noticeable ecological effect on benthos populations.
+
+=== Other research ===

data/en.wikipedia.org/wiki/Benthic_zone-4.md

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+---
+title: "Benthic zone"
+chunk: 5/5
+source: "https://en.wikipedia.org/wiki/Benthic_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:28.462475+00:00"
+instance: "kb-cron"
+---
+
+Benthic macroinvertebrates have many important ecological functions, such as regulating the flow of materials and energy in river ecosystems through their food web linkages. Because of this correlation between flow of energy and nutrients, benthic macroinvertebrates have the ability to influence food resources on fish and other organisms in aquatic ecosystems. For example, the addition of a moderate amount of nutrients to a river over the course of several years resulted in increases in invertebrate richness, abundance, and biomass. These in turn resulted in increased food resources for native species of fish with insignificant alteration of the macroinvertebrate community structure and trophic pathways. The presence of macroinvertebrates such as Amphipoda also affect the dominance of certain types of algae in Benthic ecosystems as well. In addition, because benthic zones are influenced by the flow of dead organic material, there have been studies conducted on the relationship between stream and river water flows and the resulting effects on the benthic zone. Low flow events show a restriction in nutrient transport from benthic substrates to food webs, and caused a decrease in benthic macroinvertebrate biomass, which lead to the disappearance of food sources into the substrate.
+Because the benthic system regulates energy in aquatic ecosystems, studies have been made of the mechanisms of the benthic zone in order to better understand the ecosystem. Benthic diatoms have been used by the European Union's Water Framework Directive (WFD) to establish ecological quality ratios that determined the ecological status of lakes in the UK. Beginning research is being made on benthic assemblages to see if they can be used as indicators of healthy aquatic ecosystems. Benthic assemblages in urbanized coastal regions are not functionally equivalent to benthic assemblages in untouched regions.
+Ecologists are attempting to understand the relationship between heterogeneity and maintaining biodiversity in aquatic ecosystems. Benthic algae has been used as an inherently good subject for studying short term changes and community responses to heterogeneous conditions in streams. Understanding the potential mechanisms involving benthic periphyton and the effects on heterogeneity within a stream may provide a better understanding of the structure and function of stream ecosystems. Periphyton populations suffer from high natural spatial variability while difficult accessibility simultaneously limits the practicable number of samples that can be taken. Targeting periphyton locations which are known to provide reliable samples – especially hard surfaces – is recommended in the European Union benthic monitoring program (by Kelly 1998 for the United Kingdom then in the EU and for the EU as a whole by CEN 2003 and CEN 2004) and in some United States programs (by Moulton et al. 2002). Benthic gross primary production (GPP) may be important in maintaining biodiversity hotspots in littoral zones in large lake ecosystems. However, the relative contributions of benthic habitats within specific ecosystems are poorly explored and more research is planned.
+
+== Threats and mitigation ==
+
+Benthos are negatively impacted by fishing, pollution and litter, deep-sea mining, oil and gas activities, tourism, shipping, invasive species, climate change (and its impacts such as ocean acidification, ocean warming and changes to ocean circulation) and construction such as coastal development, undersea cables, and wind farm construction.
+
+Bottom trawling accounts for roughly 25% of global capture fisheries. It has increasingly been recognized as a non-sustainable fishing practice. It impacts benthic ecosystems in two ways. First, fishing gear disrupts epibenthic sediments, resulting in the loss of habitat complexity and resuspension of sediments into the water column, reducing the sedimentary organic-matter content, and increasing turbidity and biochemical oxygen demand in the water column. Second, trawling disrupts benthic community structure, selectively removing large-bodied target and non-target species, which are usually K-selected, resulting in a community dominated by relatively small r-selected species. Given the significance of these impacts, a number of countries have implemented total or partial bans on bottom trawling within their territorial waters  or in the international waters they manage.
+
+== See also ==
+
+== References ==
+
+== External links ==
+
+Data Archive for Seabed Species and Habitats from the UK Marine Data Archive Centre
+"Benthos"
+"Benthos". (2008) Encyclopædia Britannica. (Retrieved May 15, 2008, from Encyclopædia Britannica Online.)
+Ryan, Paddy (2007) "Benthic communities" Archived 2008-12-16 at the Wayback Machine Te Ara - the Encyclopædia of New Zealand, updated 21 September 2007.
+Yip, Maricela and Madl, Pierre (1999) "Benthos" Archived 2019-07-20 at the Wayback Machine University of Salzburg.

data/en.wikipedia.org/wiki/Cape_(geography)-0.md

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+---
+title: "Cape (geography)"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Cape_(geography)"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:31.991235+00:00"
+instance: "kb-cron"
+---
+
+In geography, a cape is a headland, peninsula or promontory extending into a body of water, usually a sea. A cape usually represents a marked change in trend of the coastline, often making them important landmarks in sea navigation. This also makes them prone to natural forms of erosion, mainly tidal actions, resulting in a relatively short geological lifespan.
+
+
+== Formation ==
+Capes can be formed by glaciers, volcanoes, and changes in sea level. Erosion plays a large role in each of these methods of formation. Coastal erosion by waves and currents can create capes by wearing away softer rock and leaving behind harder rock formations. Movements of the Earth's crust can uplift land, forming capes. For example, the Cape of Good Hope was formed by tectonic forces. Volcanic eruptions can create capes by depositing lava that solidifies into new landforms. Cape Verde, (also known as Cabo Verde) is an example of a volcanic cape. Glaciers can carve out capes by eroding the landscape as they advance and retreat. Cape Cod in the United States was formed by glacial activity during the last Ice Age.
+
+
+== Importance in navigation ==
+Capes (and other headlands) are conspicuous visual landmarks along a coast, and sailors have relied on them for navigation since antiquity. The Greeks and Romans considered some to be sacred capes and erected temples to the sea god nearby.
+Greek peripli describe capes and other headlands a sailor will encounter along a route. The Periplus of Pseudo-Scylax, for instance, illustrates a clockwise journey around Sicily using three capes that define its triangular shape: Cape Peloro in the northeast, Cape Pachynus in the southeast, and Cape Lilybaeum in the west. Sicily itself was referred to as Trinacria (or Three Capes) in antiquity.
+Homer's works reference a number of capes to describe journeys around the Mediterranean Sea. Menelaus, Agamemnon, and Odysseus each faced peril at the notoriously dangerous Cape Malea at the southeastern tip of the Peloponnese. Menelaus navigated via Cape Sounion on his way home from Troy, and Nestor stopped at Cape Geraestus (now Cape Mandelo) on Euboea to give offerings at the altar to Poseidon there.
+Cape Gelidonya (then known as Chelidonia) on the coast of Turkey served as a bearing aid for ships heading to the Egyptian port of Canopus, directly to the south. Cape Sidero on the eastern tip of Crete was a waypoint for Jason and the Argonauts returning from Libya as well as for Paul the Apostle as he traveled from Caesarea to Rome.
+The three great capes (Africa's Cape of Good Hope, Australia's Cape Leeuwin, and South America's Cape Horn) defined the traditional clipper route between Europe and the Far East, Australia and New Zealand. They continue to be important landmarks in ocean yacht racing.
+
+
+== List of capes ==
+
+
+=== Antarctica ===
+Cape Ann
+Cape May (Antarctica), McMurdo Sound
+
+
+=== Australia ===
+Cape Flattery (Queensland)
+Cape Howe
+Cape Leeuwin
+Cape York (Queensland)
+Cape Byron 
+
+
+=== Canada ===
+Anse du Cap des Rosiers
+Cape Blomidon
+Cape Kildare
+Cape North
+Cape Race
+Cape Sable
+Cape Spear
+Cape St Mary
+Cape St Mary's
+Cape Traverse
+Crown Point
+North Cape
+Cape Breton
+
+
+=== Chile ===
+Cape Horn
+
+
+=== France ===
+Cap Blanc Nez
+Cap Gris Nez
+Cap d'Antifer, Seine-Maritime
+Cap d'Antifer Lighthouse
+fr:Cap de la Hève
+fr:Cap Lévy
+Cap de la Hague
+fr:Cap de Carteret
+Cap Fréhel
+Cap de la Chèvre
+Cap Ferret
+Cap Cerbère
+fr:Cap Leucate
+Cap Couronne
+fr:Phare de Cap Couronne, Lighthouse of Cape Couronne
+fr:Cap Croisette
+Cap Sicié
+fr:Cap Bénat
+fr:Cap Cartaya
+Cap Carmat
+Cap de St-Tropez
+fr:Cap d'Antibes
+fr: Cap Ferrat
+Cap-d'Ail
+Roquebrune-Cap-Martin
+
+
+=== India ===
+Cape Comorin
+
+
+=== Indonesia ===
+Tanjung Selatan
+Tanjung Benoa
+
+
+=== Italy ===
+it:Capo Mele
+Capo di Noli, Noli
+Capo di Vado, Bergeggi
+Capo d'Anzio
+Capo d'Anzio Lighthouse
+Capo Circeo
+Capo Miseno
+Capo Sottile
+Capo d'Orso
+Capo d'Orso Lighthouse
+Capo Palinuro
+Capo Scalea
+Cittadella del Capo
+Capo Vaticano
+Capo Suvero
+Capo Peloro
+Capo di Milazzo
+it:Capo Calavà
+Capo d'Orlando
+Capo Plaia
+Capo Zafferano
+Capo Gallo
+it:Capo San Vito
+it:Capo Feto
+Capo Granitola
+Capo San Marco
+it:Capo Bianco
+it:Capo Santa Panagia
+Capo Santa Croce
+Capo Canpolato
+Capo Schisò
+Capo dell'Armi
+it:Capo Spartivento
+Capo Bruzzano
+Capo Rizzuto
+Capo Colonna, home to the remaining column of the Temple of Hera Lacinia
+Capo Trionto
+it:Capo Spulico
+Capo San Vito
+Torre del Pizzo
+Capo Santa Maria di Leuca
+Capo San Gennaro
+Capo di Torre Cavallo
+Punta Cavalluccio
+it:Punta Ferruccio
+
+
+=== Malaysia ===
+Tanjung Datu
+Tanjung Piai
+Tanjung Tuan
+
+
+=== Portugal ===
+Cabo da Roca
+
+
+=== United States ===
+Cape Ann, Massachusetts
+Cape Cod, Massachusetts
+Cape May, New Jersey
+Cape Charles, Virginia
+Cape Henry, Virginia
+Cape Hatteras, North Carolina
+Cape Lookout, North Carolina
+Cape Fear, North Carolina
+Cape Canaveral, Florida
+Cape Canaveral Space Force Station, a launch station of the US Space Force
+Cape Coral, Florida
+Cape Rosier, Maine
+
+
+=== Spain ===
+Cabo Higer, Akartegi
+Cabo Ogoño, Bizkaia
+Cabo Matxitxako, Bermeo
+Cabo de Billao, Bizkaia
+es:Cabo de Ajo, Cantabria
+es:Cape Mayor, Santander, Cantabria
+Cabo de Oyambre, Cantabria
+Cabo Prieto, Llanes Asturias
+Cabo Lastres, Colunga Asturias
+es:Cabo Torres, Gijón
+Cabo de Peñas, Peñes
+es:Cabo Vidio, Cudillero
+Cabo Busto, Asturias
+Cabo Cebes, Tapia de Casariego
+Cabo Burela, Burela
+Cabo de Morás, Lugo
+Cabo Ortegal, La Coruña
+es:Cabo Prior, Ferrol
+Cabo Prioriño Grande, Ferrol
+Cabo Santo Adrián, La Coruña
+Cabo de Laxe, La Coruña
+Cabo do Trece, La Coruña
+Cape Vilan, La Coruña
+Cabo Touriñán, Muxía
+Cabo da Nave, La Coruña
+Cape Finisterre, La Coruña, Galicia
+Cabo Corrubedo, Ribeira
+Cabo Urda, Bueu
+es:Cabo Home, Cangas
+es:Cabo Silleiro, Pontevedra
+
+
+=== South Africa ===
+Cape of Good Hope, a headland on the southwest coast of South Africa, when referred to as the Cape, a metonym for:
+Dutch Cape Colony, a colony of the Dutch East India company
+Cape Colony, a British colony in South Africa that replaced the Dutch Cape Colony
+Cape Province, a former province of South Africa formed from the Cape Colony
+Cape Town, a city in South Africa, and surrounding areas
+
+
+== Gallery ==
+
+
+== See also ==
+Extreme points of Africa
+Extreme points of Antarctica
+Extreme points of Asia
+Extreme points of Australia
+Extreme points of Europe
+Extreme points of North America
+Extreme points of South America
+
+
+== Notes ==
+
+
+== References ==
+
+
+== External links ==
+ Media related to Capes (geography) at Wikimedia Commons

data/en.wikipedia.org/wiki/Capillary_wave-0.md

@@ -0,0 +1,493 @@
+---
+title: "Capillary wave"
+chunk: 1/2
+source: "https://en.wikipedia.org/wiki/Capillary_wave"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:33.305688+00:00"
+instance: "kb-cron"
+---
+
+A capillary wave is a wave traveling along the phase boundary of a fluid, whose dynamics and phase velocity are dominated by the effects of surface tension.
+Capillary waves are common in nature, and are often referred to as ripples.  The wavelength of capillary waves on water is typically less than a few centimeters, with a phase speed in excess of 0.2–0.3 meter/second.
+A longer wavelength on a fluid interface will result in gravity–capillary waves which are influenced by both the effects of surface tension and gravity, as well as by fluid inertia. Ordinary gravity waves have a still longer wavelength.
+Light breezes upon the surface of water which stir up such small ripples are also sometimes referred to as 'cat's paws'. On the open ocean, much larger ocean surface waves (seas and swells) may result from coalescence of smaller wind-caused ripple-waves.
+
+== Dispersion relation ==
+The dispersion relation describes the relationship between wavelength and frequency in waves. Distinction can be made between pure capillary waves – fully dominated by the effects of surface tension – and gravity–capillary waves which are also affected by gravity.
+
+=== Capillary waves, proper ===
+The dispersion relation for capillary waves is
+
+  
+    
+      
+        
+          ω
+          
+            2
+          
+        
+        =
+        
+          
+            σ
+            
+              ρ
+              +
+              
+                ρ
+                ′
+              
+            
+          
+        
+        
+        
+          |
+        
+        k
+        
+          
+            |
+          
+          
+            3
+          
+        
+        ,
+      
+    
+    {\displaystyle \omega ^{2}={\frac {\sigma }{\rho +\rho '}}\,|k|^{3},}
+  
+
+where 
+  
+    
+      
+        ω
+      
+    
+    {\displaystyle \omega }
+  
+ is the angular frequency, 
+  
+    
+      
+        σ
+      
+    
+    {\displaystyle \sigma }
+  
+ the surface tension, 
+  
+    
+      
+        ρ
+      
+    
+    {\displaystyle \rho }
+  
+ the density of the 
+heavier fluid, 
+  
+    
+      
+        
+          ρ
+          ′
+        
+      
+    
+    {\displaystyle \rho '}
+  
+ the density of the lighter fluid and 
+  
+    
+      
+        k
+      
+    
+    {\displaystyle k}
+  
+ the wavenumber. The wavelength is 
+
+  
+    
+      
+        λ
+        =
+        
+          
+            
+              2
+              π
+            
+            k
+          
+        
+        .
+      
+    
+    {\displaystyle \lambda ={\frac {2\pi }{k}}.}
+  
+
+For the boundary between fluid and vacuum (free surface), the dispersion relation reduces to
+
+  
+    
+      
+        
+          ω
+          
+            2
+          
+        
+        =
+        
+          
+            σ
+            ρ
+          
+        
+        
+        
+          |
+        
+        k
+        
+          
+            |
+          
+          
+            3
+          
+        
+        .
+      
+    
+    {\displaystyle \omega ^{2}={\frac {\sigma }{\rho }}\,|k|^{3}.}
+  
+
+=== Gravity–capillary waves ===
+
+When capillary waves are also affected substantially by gravity, they are called gravity–capillary waves. Their dispersion relation reads, for waves on the interface between two fluids of infinite depth:
+
+  
+    
+      
+        
+          ω
+          
+            2
+          
+        
+        =
+        
+          |
+        
+        k
+        
+          |
+        
+        
+          (
+          
+            
+              
+                
+                  ρ
+                  −
+                  
+                    ρ
+                    ′
+                  
+                
+                
+                  ρ
+                  +
+                  
+                    ρ
+                    ′
+                  
+                
+              
+            
+            g
+            +
+            
+              
+                σ
+                
+                  ρ
+                  +
+                  
+                    ρ
+                    ′
+                  
+                
+              
+            
+            
+              k
+              
+                2
+              
+            
+          
+          )
+        
+        ,
+      
+    
+    {\displaystyle \omega ^{2}=|k|\left({\frac {\rho -\rho '}{\rho +\rho '}}g+{\frac {\sigma }{\rho +\rho '}}k^{2}\right),}
+  
+
+where 
+  
+    
+      
+        g
+      
+    
+    {\displaystyle g}
+  
+ is the acceleration due to gravity, 
+  
+    
+      
+        ρ
+      
+    
+    {\displaystyle \rho }
+  
+ and 
+  
+    
+      
+        
+          ρ
+          ′
+        
+      
+    
+    {\displaystyle \rho '}
+  
+ are the densities of the two fluids 
+  
+    
+      
+        (
+        ρ
+        >
+        
+          ρ
+          ′
+        
+        )
+      
+    
+    {\displaystyle (\rho >\rho ')}
+  
+. The factor 
+  
+    
+      
+        (
+        ρ
+        −
+        
+          ρ
+          ′
+        
+        )
+        
+          /
+        
+        (
+        ρ
+        +
+        
+          ρ
+          ′
+        
+        )
+      
+    
+    {\displaystyle (\rho -\rho ')/(\rho +\rho ')}
+  
+ in the first term is the Atwood number.
+
+==== Gravity wave regime ====
+
+For large wavelengths (small 
+  
+    
+      
+        k
+        =
+        2
+        π
+        
+          /
+        
+        λ
+      
+    
+    {\displaystyle k=2\pi /\lambda }
+  
+), only the first term is relevant and one has gravity waves.
+In this limit, the waves have a group velocity half the phase velocity: following a single wave's crest in a group one can see the wave appearing at the back of the group, growing and finally disappearing at the front of the group.
+
+==== Capillary wave regime ====
+Shorter (large 
+  
+    
+      
+        k
+      
+    
+    {\displaystyle k}
+  
+) waves (e.g. 2 mm for the water–air interface), which are proper capillary waves, do the opposite: an individual wave appears at the front of the group, grows when moving towards the group center and finally disappears at the back of the group. Phase velocity is two thirds of group velocity in this limit.
+
+==== Phase velocity minimum ====
+Between these two limits is a point at which the dispersion caused by gravity cancels out the dispersion due to the capillary effect.  At a certain wavelength, the group velocity equals the phase velocity, and there is no dispersion. At precisely this same wavelength, the phase velocity of gravity–capillary waves as a function of wavelength (or wave number) has a minimum. Waves with wavelengths much smaller than this critical wavelength 
+  
+    
+      
+        
+          λ
+          
+            m
+          
+        
+      
+    
+    {\displaystyle \lambda _{m}}
+  
+ are dominated by surface tension, and much above by gravity. The value of this wavelength and the associated minimum phase speed 
+  
+    
+      
+        
+          c
+          
+            m
+          
+        
+      
+    
+    {\displaystyle c_{m}}
+  
+ are:
+
+  
+    
+      
+        
+          λ
+          
+            m
+          
+        
+        =
+        2
+        π
+        
+          
+            
+              σ
+              
+                (
+                ρ
+                −
+                
+                  ρ
+                  ′
+                
+                )
+                g
+              
+            
+          
+        
+        
+        
+          and
+        
+        
+        
+          c
+          
+            m
+          
+        
+        =
+        
+          
+            
+              
+                2
+                
+                  
+                    (
+                    ρ
+                    −
+                    
+                      ρ
+                      ′
+                    
+                    )
+                    g
+                    σ
+                  
+                
+              
+              
+                ρ
+                +
+                
+                  ρ
+                  ′
+                
+              
+            
+          
+        
+        .
+      
+    
+    {\displaystyle \lambda _{m}=2\pi {\sqrt {\frac {\sigma }{(\rho -\rho ')g}}}\quad {\text{and}}\quad c_{m}={\sqrt {\frac {2{\sqrt {(\rho -\rho ')g\sigma }}}{\rho +\rho '}}}.}
+  
+
+For the air–water interface, 
+  
+    
+      
+        
+          λ
+          
+            m
+          
+        
+      
+    
+    {\displaystyle \lambda _{m}}
+  
+ is found to be 1.7 cm (0.67 in), and 
+  
+    
+      
+        
+          c
+          
+            m
+          
+        
+      
+    
+    {\displaystyle c_{m}}
+  
+ is 0.23 m/s (0.75 ft/s).
+If one drops a small stone or droplet into liquid, the waves then propagate outside an expanding circle of fluid at rest; this circle is a caustic which corresponds to the minimal group velocity.

data/en.wikipedia.org/wiki/Capillary_wave-1.md

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+---
+title: "Capillary wave"
+chunk: 2/2
+source: "https://en.wikipedia.org/wiki/Capillary_wave"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:33.305688+00:00"
+instance: "kb-cron"
+---
+
+==== Derivation ====
+As Richard Feynman put it, "[water waves] that are easily seen by everyone and which are usually used as an example of waves in elementary courses [...] are the worst possible example [...]; they have all the complications that waves can have." The derivation of the general dispersion relation is therefore quite involved.
+There are three contributions to the energy, due to gravity, to surface tension, and to hydrodynamics. The first two are potential energies, and responsible for the two terms inside the parenthesis, as is clear from the appearance of 
+  
+    
+      
+        g
+      
+    
+    {\displaystyle g}
+  
+ and 
+  
+    
+      
+        σ
+      
+    
+    {\displaystyle \sigma }
+  
+. For gravity, an assumption is made of the density of the fluids being constant (i.e., incompressibility), and likewise 
+  
+    
+      
+        g
+      
+    
+    {\displaystyle g}
+  
+ (waves are not high enough for gravitation to change appreciably). For surface tension, the deviations from planarity (as measured by derivatives of the surface) are supposed to be small. For common waves both approximations are good enough.
+The third contribution involves the kinetic energies of the fluids. It is the most complicated and calls for a hydrodynamic framework. Incompressibility is again involved (which is satisfied if the speed of the waves is much less than the speed of sound in the media), together with the flow being irrotational – the flow is then potential. These are typically also good approximations for common situations.
+The resulting equation for the potential (which is Laplace equation) can be solved with the proper boundary conditions. On one hand, the velocity must vanish well below the surface (in the "deep water" case, which is the one we consider, otherwise a more involved result is obtained, see Ocean surface waves.) On the other, its vertical component must match the motion of the surface. This contribution ends up being responsible for the extra  
+  
+    
+      
+        k
+      
+    
+    {\displaystyle k}
+  
+ outside the parenthesis, which causes all regimes to be dispersive, both at low values of 
+  
+    
+      
+        k
+      
+    
+    {\displaystyle k}
+  
+, and high ones (except around the one value at which the two dispersions cancel out.)
+
+== See also ==
+Capillary action
+Dispersion (water waves)
+Ocean surface wave
+Thermal capillary wave
+Two-phase flow
+Wave-formed ripple
+
+== Gallery ==
+
+== Notes ==
+
+== References ==
+Longuet-Higgins, M. S. (1963). "The generation of capillary waves by steep gravity waves". Journal of Fluid Mechanics. 16 (1): 138–159. Bibcode:1963JFM....16..138L. doi:10.1017/S0022112063000641. ISSN 1469-7645. S2CID 119740891.
+Lamb, H. (1994). Hydrodynamics (6th ed.). Cambridge University Press. ISBN 978-0-521-45868-9.
+Phillips, O. M. (1977). The dynamics of the upper ocean (2nd ed.). Cambridge University Press. ISBN 0-521-29801-6.
+Dingemans, M. W. (1997). Water wave propagation over uneven bottoms. Advanced Series on Ocean Engineering. Vol. 13. World Scientific, Singapore. pp. 2 Parts, 967 pages. ISBN 981-02-0427-2.
+Safran, Samuel (1994). Statistical thermodynamics of surfaces, interfaces, and membranes. Addison-Wesley.
+Tufillaro, N. B.; Ramshankar, R.; Gollub, J. P. (1989). "Order-disorder transition in capillary ripples". Physical Review Letters. 62 (4): 422–425. Bibcode:1989PhRvL..62..422T. doi:10.1103/PhysRevLett.62.422. PMID 10040229.
+
+== External links ==
+
+Capillary waves entry at sklogwiki

data/en.wikipedia.org/wiki/Coast-0.md

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+---
+title: "Coast"
+chunk: 1/4
+source: "https://en.wikipedia.org/wiki/Coast"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:34.633460+00:00"
+instance: "kb-cron"
+---
+
+A coast (also called the coastline, shoreline, or seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, such as that caused by waves. The geological composition of rock and soil dictates the type of shore that is created. Earth has about 620,000.0 km (385,250.1 mi) of coastline.
+Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity. On land, they harbor ecosystems, such as freshwater or estuarine wetlands, that are important for birds and other terrestrial animals. In wave-protected areas, coasts harbor salt marshes, mangroves, and seagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic animals. Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals (e.g. mussels, starfish, barnacles) and various kinds of seaweeds.
+In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past and present, and the beach is at the edge of the shore, including the intertidal zone where there is one. Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found at depths of 1–50 m (3.3–164.0 ft).
+According to an atlas prepared by the United Nations, about 44% of the human population lives within 150 km (93 mi) of the sea as of 2013. Due to its importance in society and its high population concentrations, the coast is important for major parts of the global food and economic system, and they provide many ecosystem services to humankind. For example, important human activities happen in port cities. Coastal fisheries (commercial, recreational, and subsistence) and aquaculture are major economic activities and create jobs, livelihoods, and protein for the majority of coastal human populations. Other coastal spaces like beaches and seaside resorts generate large revenues through tourism.
+Marine coastal ecosystems can also provide protection against sea level rise and tsunamis. In many countries, mangroves are the primary source of wood for fuel (e.g. charcoal) and building material. Coastal ecosystems like mangroves and seagrasses have a much higher capacity for carbon sequestration than many terrestrial ecosystems, and as such can play a critical role in the near-future to help mitigate climate change effects by uptake of atmospheric anthropogenic carbon dioxide. 
+However, the economic importance of coasts makes many of these communities vulnerable to climate change, which causes increases in extreme weather and sea level rise, as well as related issues like coastal erosion, saltwater intrusion, and coastal flooding. Other coastal issues, such as marine pollution, marine debris, coastal development, and marine ecosystem destruction, further complicate the human uses of the coast and threaten coastal ecosystems.
+The interactive effects of climate change, habitat destruction, overfishing, and water pollution (especially eutrophication) have led to the demise of coastal ecosystem around the globe. This has resulted in population collapse of fisheries stocks, loss of biodiversity, increased invasion of alien species, and loss of healthy habitats. International attention to these issues has been captured in Sustainable Development Goal 14 "Life Below Water", which sets goals for international policy focused on preserving marine coastal ecosystems and supporting more sustainable economic practices for coastal communities. Likewise, the United Nations has declared 2021–2030 the UN Decade on Ecosystem Restoration, but restoration of coastal ecosystems has received insufficient attention.
+Since coasts are constantly changing, a coastline's exact perimeter cannot be determined; this measurement challenge is called the coastline paradox. The term coastal zone is used to refer to a region where interactions of sea and land processes occur. Both the terms coast and coastal are often used to describe a geographic location or region located on a coastline (e.g., New Zealand's West Coast, or the East, West, and Gulf Coast of the United States.) Coasts with a narrow continental shelf that are close to the open ocean are called pelagic coast, while other coasts are more sheltered coast in a gulf or bay. A shore, on the other hand, may refer to parts of land adjoining any large body of water, including oceans (sea shore) and lakes (lake shore). 
+
+== Size ==
+
+The Earth has approximately 620,000 kilometres (390,000 mi) of coastline. Coastal habitats, which extend to the margins of the continental shelves, make up about 7 percent of the Earth's oceans, but at least 85% of commercially harvested fish depend on coastal environments during at least part of their life cycle. As of October 2010, about 2.86% of exclusive economic zones were part of marine protected areas.
+The definition of coasts varies. Marine scientists think of the "wet" (aquatic or intertidal) vegetated habitats as being coastal ecosystems (including seagrass, salt marsh etc.) whilst some terrestrial scientists might only think of coastal ecosystems as purely terrestrial plants that live close to the seashore (see also estuaries and coastal ecosystems).
+While there is general agreement in the scientific community regarding the definition of coast, in the political sphere, the delineation of the extents of a coast differ according to jurisdiction. Government authorities in various countries may define coast differently for economic and social policy reasons. 
+
+=== Challenges of precisely measuring the coastline ===
+
+== Formation ==

data/en.wikipedia.org/wiki/Coast-1.md

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+---
+title: "Coast"
+chunk: 2/4
+source: "https://en.wikipedia.org/wiki/Coast"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:34.633460+00:00"
+instance: "kb-cron"
+---
+
+Tides often determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up the river estuaries from the ocean.
+Geologists classify coasts on the basis of tidal range into macrotidal coasts with a tidal range greater than 4 m (13 ft); mesotidal coasts with a tidal range of 2 to 4 m (6.6 to 13 ft); and microtidal coasts with a tidal range of less than 2 m (7 ft). The distinction between macrotidal and mesotidal coasts is more important. Macrotidal coasts lack barrier islands and lagoons, and are characterized by funnel-shaped estuaries containing sand ridges aligned with tidal currents. Wave action is much more important for determining bedforms of sediments deposited along mesotidal and microtidal coasts than in macrotidal coasts.
+Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more sediment it moves. Coastlines with longer shores have more room for the waves to disperse their energy, while coasts with cliffs and short shore faces give little room for the wave energy to be dispersed. In these areas, the wave energy breaking against the cliffs is higher, and air and water are compressed into cracks in the rock, forcing the rock apart, breaking it down. Sediment deposited by waves comes from eroded cliff faces and is moved along the coastline by the waves. This forms an abrasion or cliffed coast.
+Sediment deposited by rivers is the dominant influence on the amount of sediment located in the case of coastlines that have estuaries. Today, riverine deposition at the coast is often blocked by dams and other human regulatory devices, which remove the sediment from the stream by causing it to be deposited inland. Coral reefs are a provider of sediment for coastlines of tropical islands.
+Like the ocean which shapes them, coasts are a dynamic environment with constant change. The Earth's natural processes, particularly sea level rises, waves and various weather phenomena, have resulted in the erosion, accretion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys (rias).
+
+== Importance for humans and ecosystems ==
+
+=== Human settlements ===
+
+More and more of the world's people live in coastal regions. According to a United Nations atlas, 44% of all people live within 150 km (93 mi) of the sea. Many major cities are on or near good harbors and have port facilities. Some landlocked places have achieved port status by building canals.
+
+Nations defend their coasts against military invaders, smugglers and illegal migrants. Fixed coastal defenses have long been erected in many nations, and coastal countries typically have a navy and some form of coast guard.
+
+==== Tourism ====
+Coasts, especially those with beaches and warm water, attract tourists often leading to the development of seaside resort communities. In many island nations such as those of the Mediterranean, South Pacific Ocean and Caribbean, tourism is central to the economy. Coasts offer recreational activities such as swimming, fishing, surfing, boating, and sunbathing. 
+
+Growth management and coastal management can be a challenge for coastal local authorities who often struggle to provide the infrastructure required by new residents, and poor management practices of construction often leave these communities and infrastructure vulnerable to processes like coastal erosion and sea level rise. In many of these communities, management practices such as beach nourishment or when the coastal infrastructure is no longer financially sustainable, managed retreat to remove communities from the coast.
+
+=== Ecosystem services ===
+
+== Types ==
+
+=== Emergent coastline ===
+
+According to one principle of classification, an emergent coastline is a coastline that has experienced a fall in sea level, because of either a global sea-level change, or local uplift. Emergent coastlines are identifiable by the coastal landforms, which are above the high tide mark, such as raised beaches. In contrast, a submergent coastline is one where the sea level has risen, due to a global sea-level change, local subsidence, or isostatic rebound. Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as rias (drowned valleys) and fjords
+
+=== Concordant coastline ===
+
+According to the second principle of classification, a concordant coastline is a coastline where bands of different rock types run parallel to the shore. These rock types are usually of varying resistance, so the coastline forms distinctive landforms, such as coves. Discordant coastlines feature distinctive landforms because the rocks are eroded by the ocean waves. The less resistant rocks erode faster, creating inlets or bay; the more resistant rocks erode more slowly, remaining as headlands or outcroppings.
+
+=== High and low energy coasts ===
+Parts of a coastline can be categorised as high energy coast or low energy coast. The distinguishing characteristics of a high energy coast are that the average wave energy is relatively high so that erosion of small grained material tends to exceed deposition, and consequently landforms like cliffs, headlands and wave-cut terraces develop. Low energy coasts are generally sheltered from waves, or in regions where the average wind wave and swell conditions are relatively mild. Low energy coasts typically change slowly, and tend to be depositional environments. 
+High energy coasts are exposed to the direct impact of waves and storms, and are generally erosional environments. High energy storm events can make large changes to a coastline, and can move significant amounts of sediment over a short period, sometimes changing a shoreline configuration.

data/en.wikipedia.org/wiki/Coast-2.md

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+---
+title: "Coast"
+chunk: 3/4
+source: "https://en.wikipedia.org/wiki/Coast"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:34.633460+00:00"
+instance: "kb-cron"
+---
+
+==== Destructive and constructive waves ====
+Swash is the shoreward flow after the break, backwash is the water flow back down the beach. The relative strength of flow in the swash and backwash determines what size grains are deposited or eroded. This is dependent on how the wave breaks and the slope of the shore.
+Depending on the form of the breaking wave, its energy can carry granular material up the beach and deposit it, or erode it by carrying more material down the slope than up it. Steep waves that are close together and break with the surf plunging down onto the shore slope expend much of their energy lifting the sediment. The weak swash does not carry it far up the slope, and the strong backwash carries it further down the slope, where it either settles in deeper water or is carried along the shore by a longshore current induced by an angled approach of the wave-front to the shore. These waves which erode the beach are called destructive waves.
+Low waves that are further apart and break by spilling, expend more of their energy in the swash which carries particles up the beach, leaving less energy for the backwash to transport them downslope, with a net constrictive influence on the beach.
+
+=== Rivieras ===
+
+Riviera is an Italian word for "shoreline", ultimately derived from Latin ripa ("riverbank"). It came to be applied as a proper name to the coast of the Ligurian Sea, in the form riviera ligure, then shortened to riviera.  Historically, the Ligurian Riviera extended from Capo Corvo (Punta Bianca) south of Genoa, north and west into what is now French territory past Monaco and sometimes as far as Marseille. Today, this coast is divided into the Italian Riviera and the French Riviera, although the French use the term "Riviera" to refer to the Italian Riviera and call the French portion the "Côte d'Azur".
+As a result of the fame of the Ligurian rivieras, the term came into English to refer to any shoreline, especially one that is sunny, topographically diverse and popular with tourists. Such places using the term include the Australian Riviera in Queensland and the Turkish Riviera along the Aegean Sea.
+
+=== Other coastal categories ===
+A cliffed coast or abrasion coast is one where marine action has produced steep declivities known as cliffs.
+A flat coast is one where the land gradually descends into the sea.
+A graded shoreline is one where wind and water action has produced a flat and straight coastline.
+A primary coast isone which is mainly undergoing early stage development by major long-term processes such as tectonism and climate change A secondary coast is one where the primary processes have mostly stabilised, and more localised processes have become prominent.
+An erosional coast is on average undergoing erosion, while a depositional coast is accumulating material.
+An active coast is on the edge of a tectonic plate, while a passive coast is usually on a substantial continental shelf or away from a plate edge.
+
+== Landforms ==
+The following articles describe some coastal landforms:
+
+=== Cliff erosion ===
+Much of the sediment deposited along a coast is the result of erosion of a surrounding cliff, or bluff. Sea cliffs retreat landward because of the constant undercutting of slopes by waves. If the slope/cliff being undercut is made of unconsolidated sediment it will erode at a much faster rate than a cliff made of bedrock.
+A natural arch is formed when a headland is eroded through by waves.
+Sea caves are made when certain rock beds are more susceptible to erosion than the surrounding rock beds because of different areas of weakness. These areas are eroded at a faster pace creating a hole or crevice that, through time, by means of wave action and erosion, becomes a cave.
+A stack is formed when a headland is eroded away by wave and wind action or an arch collapses leaving an offshore remnant.
+A stump is a shortened sea stack that has been eroded away or fallen because of instability.
+Wave-cut notches are caused by the undercutting of overhanging slopes which leads to increased stress on cliff material and a greater probability that the slope material will fall. The fallen debris accumulates at the bottom of the cliff and is eventually removed by waves.
+A wave-cut platform forms after erosion and retreat of a sea cliff has been occurring for a long time. Gently sloping wave-cut platforms develop early on in the first stages of cliff retreat. Later, the length of the platform decreases because the waves lose their energy as they break further offshore.
+
+=== Coastal features formed by sediment ===
+
+=== Coastal features formed by another feature ===
+Estuary
+Lagoon
+Salt marsh
+Mangrove forests
+Kelp forests
+Coral reefs
+Oyster reefs
+
+=== Other features on the coast ===
+
+== Coastal waters ==

data/en.wikipedia.org/wiki/Coast-3.md

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+---
+title: "Coast"
+chunk: 4/4
+source: "https://en.wikipedia.org/wiki/Coast"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:34.633460+00:00"
+instance: "kb-cron"
+---
+
+"Coastal waters" (or "coastal seas") is a term that carries different meanings depending upon the context, ranging from a geographic reference to the waters within a few kilometers of the coast, to describing the entire continental shelf that may stretch for more than a hundred kilometers from land. The term is used in a different manner when describing legal and economic boundaries, such as territorial waters and international waters, or when describing the geography of coastal landforms or the ecological systems operating through the continental shelf (marine coastal ecosystems).
+The dynamic fluid nature of the ocean means that all components of the whole ocean system are ultimately connected, although certain regional classifications are useful and relevant. The waters of the continental shelves represent such a region. The term "coastal waters" has been used in a wide variety of different ways in different contexts. In European Union environmental management it extends from the coast to just a few nautical miles while in the United States the US EPA considers this region to extend much further offshore. 
+"Coastal waters" has specific meanings in the context of commercial coastal shipping, and somewhat different meanings in the context of naval littoral warfare. Oceanographers and marine biologists have yet other takes. Coastal waters have a wide range of marine habitats from enclosed estuaries to the open waters of the continental shelf.   
+Similarly, the term littoral zone has no single definition. It is the part of a sea, lake, or river that is close to the shore. In coastal environments, the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged.
+Coastal waters can be threatened by coastal eutrophication and harmful algal blooms.
+
+== In geology ==
+The identification of bodies of rock formed from sediments deposited in shoreline and nearshore environments (shoreline and nearshore facies) is extremely important to geologists. These provide vital clues for reconstructing the geography of ancient continents (paleogeography). The locations of these beds show the extent of ancient seas at particular points in geological time, and provide clues to the magnitudes of tides in the distant past.
+Sediments deposited in the shoreface are preserved as lenses of sandstone in which the upper part of the sandstone is coarser than the lower part (a coarsening upwards sequence). Geologists refer to these are parasequences. Each records an episode of retreat of the ocean from the shoreline over a period of 10,000 to 1,000,000 years. These often show laminations reflecting various kinds of tidal cycles.
+Some of the best-studied shoreline deposits in the world are found along the former western shore of the Western Interior Seaway, a shallow sea that flooded central North America during the late Cretaceous Period (about 100 to 66 million years ago). These are beautifully exposed along the Book Cliffs of Utah and Colorado.
+
+=== Geologic processes ===
+The following articles describe the various geologic processes that affect a coastal zone:
+
+== Wildlife ==
+
+=== Animals ===
+
+Larger animals that live in coastal areas include puffins, sea turtles and rockhopper penguins, among many others. Sea snails and various kinds of barnacles live on rocky coasts and scavenge on food deposited by the sea. Some coastal animals are used to humans in developed areas, such as dolphins and seagulls who eat food thrown for them by tourists. Since the coastal areas are all part of the littoral zone, there is a profusion of marine life found just off-coast, including sessile animals such as corals, sponges, starfish, mussels, seaweeds, fishes, and sea anemones.
+There are many kinds of seabirds on various coasts. These include pelicans and cormorants, who join up with terns and oystercatchers to forage for fish and shellfish. There are sea lions on the coast of Wales and other countries.
+
+==== Coastal fish ====
+
+=== Plants ===
+Many coastal areas are famous for their kelp beds. Kelp is a fast-growing seaweed that can grow up to half a meter a day in ideal conditions. Mangroves, seagrasses, macroalgal beds, and salt marsh are important coastal vegetation types in tropical and temperate environments respectively. Restinga is another type of coastal vegetation.
+
+== Threats ==
+
+Coasts also face many human-induced environmental impacts and coastal development hazards. The most important ones are: 
+
+Pollution which can be in the form of water pollution, nutrient pollution (leading to coastal eutrophication and harmful algal blooms), oil spills or marine debris that is contaminating coasts with plastic and other trash.
+Sea level rise, and associated issues like coastal erosion and saltwater intrusion.
+
+=== Pollution ===
+
+The pollution of coastlines is connected to marine pollution which can occur from a number of sources: Marine debris (garbage and industrial debris); the transportation of petroleum in tankers, increasing the probability of large oil spills; small oil spills created by large and small vessels, which flush bilge water into the ocean.
+
+==== Marine pollution ====
+
+==== Marine debris ====
+
+==== Microplastics ====
+
+=== Sea level rise due to climate change ===
+
+== Global goals ==
+International attention to address the threats of coasts has been captured in Sustainable Development Goal 14 "Life Below Water" which sets goals for international policy focused on preserving marine coastal ecosystems and supporting more sustainable economic practices for coastal communities. Likewise, the United Nations has declared 2021–2030 the UN Decade on Ecosystem Restoration, but restoration of coastal ecosystems has received insufficient attention.
+
+== See also ==
+
+Bank (geography)
+Beach cleaning
+Coastal and Estuarine Research Federation
+European Atlas of the Seas
+Intertidal zone
+Land reclamation
+List of countries by length of coastline
+List of U.S. states by coastline
+Offshore or Intertidal zone
+Ballantine Scale
+Coastal path
+Shorezone
+
+== References ==
+
+== Further reading ==
+Scheffers, Anja M.; Scheffers, Sander R.; Kelletat, Dieter H. (2012). The Coastlines of the World with Google Earth: Understanding our Environment. New York: Springer. ISBN 978-94-007-0737-5.
+
+== External links ==
+Woods Hole Oceanographic Institution - organization dedicated to ocean research, exploration, and education

data/en.wikipedia.org/wiki/Cold_seep-0.md

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+---
+title: "Cold seep"
+chunk: 1/10
+source: "https://en.wikipedia.org/wiki/Cold_seep"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:36.156842+00:00"
+instance: "kb-cron"
+---
+
+A cold seep (sometimes called a cold vent) is an area of the ocean floor where seepage of fluids rich in hydrogen sulfide, methane, and other hydrocarbons occurs, often in the form of a brine pool. Cold does not mean that the temperature of the seepage is lower than that of the surrounding sea water; on the contrary, its temperature is often slightly higher. The "cold" is relative to the very warm (at least 60 °C or 140 °F) conditions of a hydrothermal vent. Cold seeps constitute a biome supporting several endemic species.
+Cold seeps develop unique topography over time, where reactions between methane and seawater create carbonate rock formations and reefs. These reactions may also be dependent on bacterial activity. Ikaite, a hydrous calcium carbonate, can be associated with oxidizing methane at cold seeps.
+
+== Types ==
+
+Types of cold seeps can be distinguished according to the depth, as shallow cold seeps and deep cold seeps. Cold seeps can also be distinguished in detail, as follows:
+
+oil/gas seeps
+gas seeps: methane seeps
+gas hydrate seeps
+brine seeps are formed in brine pools
+pockmarks
+mud volcanoes
+
+== Formation and ecological succession ==
+Cold seeps occur over fissures on the seafloor caused by tectonic activity. Oil and methane "seep" out of those fissures, get diffused by sediment, and emerge over an area several hundred meters wide.
+Methane (CH4) is the main component of natural gas. But in addition to being an important energy source for humans, methane also forms the basis of a cold seep ecosystem. Cold seep biota below 200 m (660 ft) typically exhibit much greater systematic specialization and reliance on chemoautotrophy than those from shelf depths. Deep-sea seeps sediments are highly heterogeneous. They sustain different geochemical and microbial processes that are reflected in a complex mosaic of habitats inhabited by a mixture of specialist (heterotrophic and symbiont-associated) and background fauna.
+
+=== Chemosynthetic communities ===
+
+Biological research in cold seeps and hydrothermal vents has been mostly focused on the microbiology and the prominent macro-invertebrates thriving on chemosynthetic microorganisms. Much less research has been done on the smaller benthic fraction at the size of the meiofauna (<1 mm).
+A community composition's orderly shift from one set of species to another is called ecological succession.
+The first type of organism to take advantage of this deep-sea energy source is bacteria. Aggregating into bacterial mats at cold seeps, these bacteria metabolize methane and hydrogen sulfide (another gas that emerges from seeps) for energy. This process of obtaining energy from chemicals is known as chemosynthesis.
+
+During this initial stage, when methane is relatively abundant, dense mussel beds also form near the cold seep. Mostly composed of species in the genus Bathymodiolus, these mussels are primarily nourished by symbiotic bacteria that also produce energy from methane, similar to their relatives that form mats. Bathymodiolin mussels often supplement this nutrition source by filter feeding on particulate organic matter known as marine snow. Chemosynthetic bivalves are prominent constituents of the fauna of cold seeps and are represented in that setting by five families: Solemyidae, Lucinidae, Vesicomyidae, Thyasiridae, and Mytilidae.
+This microbial activity produces calcium carbonate, which is deposited on the seafloor and forms a layer of rock. During a period lasting up to several decades, these rock formations attract siboglinid tubeworms, which settle and grow along with the mussels. Like the mussels, tubeworms rely on chemosynthetic bacteria (in this case, a type that needs hydrogen sulfide instead of methane) for survival. True to any symbiotic relationship, a tubeworm also provides for its bacteria by appropriating hydrogen sulfide from the environment. The sulfide not only comes from the water, but is also mined from the sediment through an extensive "root" system that a tubeworm "bush" establishes in the hard, carbonate substrate. A tubeworm bush can contain hundreds of individual worms, which can grow a meter or more above the sediment.
+Cold seeps do not last indefinitely. As the rate of gas seepage slowly decreases, the shorter-lived, methane-hungry mussels (or more precisely, their methane-hungry bacterial symbionts) start to die off. At this stage, tubeworms become the dominant organism in a seep community. As long as there is some sulfide in the sediment, the sulfide-mining tubeworms can persist. Individuals of one tubeworm species Lamellibrachia luymesi have been estimated to live for over 250 years in such conditions.

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+---
+title: "Cold seep"
+chunk: 2/10
+source: "https://en.wikipedia.org/wiki/Cold_seep"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:36.156842+00:00"
+instance: "kb-cron"
+---
+
+=== The Benthic Filter ===
+The organisms living at cold seeps have a large impact on the carbon cycle and on climate. Chemosynthetic organisms, specifically methanogenic (methane-consuming) organisms, prohibit the methane seeping up from beneath the seafloor from being released into the water above. Since methane is such a potent greenhouse gas, methane release could cause global warming when gas hydrate reservoirs destabilized. The consumption of methane by aerobic and anaerobic seafloor life is called "the benthic filter". The first part of this filter is the anaerobic bacteria and archaea underneath the seafloor that consume methane through the anaerobic oxidation of methane (AOM). If the flux of methane flowing through the sediment is too large, and the anaerobic bacteria and archaea are consuming the maximum amount of methane, then the excess methane is consumed by free-floating or symbiotic aerobic bacteria above the sediment at the seafloor. The symbiotic bacteria have been found in organisms such as tube worms and clams living at cold seeps; these organisms provide oxygen to the aerobic bacteria as the bacteria provide energy they obtain from the consumption of methane. Understanding how efficient the benthic filter is can help predict how much methane escapes the seafloor at cold seeps and enters the water column and eventually the atmosphere. Studies have shown that 50–90% of methane is consumed at cold seeps with bacterial mats. Areas with clam beds have less than 15% of methane escaping. Efficiency is determined by a number of factors. The benthic layer is more efficient with low flow of methane, and efficiency decreases as methane flow or the speed of flow increases. Oxygen demand for cold seep ecosystems is much higher than other benthic ecosystems, so if the bottom water does not have enough oxygen, then the efficiency of aerobic microbes in removing methane is reduced. The benthic filter cannot affect methane that is not traveling through the sediment. Methane can bypass the benthic filter if it bubbles to the surface or travels through cracks and fissures in the sediment. These organisms are the only biological sink of methane in the ocean.
+
+=== Comparison with other communities ===
+
+Cold seeps and hydrothermal vents of deep oceans are communities that do not rely on photosynthesis for food and energy production. These systems are largely driven by chemosynthetic derived energy. Both systems share common characteristics such as the presence of reduced chemical compounds (H2S and hydrocarbonates), local hypoxia or even anoxia, a high abundance and metabolic activity of bacterial populations, and the production of autochthonous, organic material by chemoautotrophic bacteria. Both hydrothermal vents and cold seeps show highly increased levels of metazoan biomass in association with a low local diversity. This is explained through the presence of dense aggregations of foundation species and epizoic animals living within these aggregations. Community-level comparisons reveal that vent, seep, and organic-fall macrofauna are very distinct in terms of composition at the family level, although they share many dominant taxa among highly sulphidic habitats.
+However, hydrothermal vents and cold seeps also differ in many ways. Compared to the more stable cold seeps, vents are characterized by locally-high temperatures, strongly fluctuating temperatures, pH, sulfide and oxygen concentrations, often the absence of sediments, a relatively young age, and often-unpredictable conditions, such as waxing and waning of vent fluids or volcanic eruptions. Unlike hydrothermal vents, which are volatile and ephemeral environments, cold seeps emit at a slow and dependable rate. Likely owing to the cooler temperatures and stability, many cold seep organisms are much longer-lived than those inhabiting hydrothermal vents.
+
+=== End of cold seep community ===
+
+Finally, as cold seeps become inactive, tubeworms also start to disappear, clearing the way for corals to settle on the now-exposed carbonate substrate. The corals do not rely on hydrocarbons seeping out of the seafloor. Studies on Lophelia pertusa suggest they derive their nutrition primarily from the ocean surface. Chemosynthesis plays only a very small role, if any, in their settlement and growth. While deepwater corals do not seem to be chemosynthesis-based organisms, the chemosynthetic organisms that come before them enable the corals' existence. This hypothesis about establishment of deep water coral reefs is called hydraulic theory.
+
+== Distribution ==
+Cold seeps were discovered in 1983 by Charles Paull and colleagues on the Florida Escarpment in the Gulf of Mexico at a depth of 3,200 meters (10,500 ft). Since then, seeps have been discovered in many other parts of the world's oceans. Most have been grouped into five biogeographic provinces: Gulf of Mexico, Atlantic, Mediterranean, East Pacific, and West Pacific, but cold seeps are also known from under the ice shelf in Antarctica, the Arctic Ocean, the North Sea, Skagerrak, Kattegat, the Gulf of California, the Red Sea, the Indian Ocean, off southern Australia, and in the inland Caspian Sea. In the Pacific Northwest, a cold seep called Pythia's Oasis was discovered in 2015. With the recent discovery of a methane seep in the Southern Ocean, cold seeps are now known in all major oceans.  Cold seeps are common along continental margins in areas of high primary productivity and tectonic activity, where crustal deformation and compaction drive emissions of methane-rich fluid. Cold seeps are patchily distributed, and they occur most frequently near ocean margins from intertidal to hadal depths. In Chile, cold seeps are known from the intertidal zone, in Kattegat, the methane seeps are known as "bubbling reefs" and are typically at depths of 0–30 m (0–100 ft), and off northern California, they can be found as shallow as 35–55 m (115–180 ft). Most cold seeps are located considerably deeper, well beyond the reach of ordinary scuba diving, and the deepest seep community known is found in the Japan Trench at a depth of 7,326 m (24,035 ft).
+In addition to cold seeps existing today, the fossil remains of ancient seep systems have been found in several parts of the world. Some of these are located far inland in places formerly covered by prehistoric oceans.
+
+=== In the Gulf of Mexico ===

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+title: "Cold seep"
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+source: "https://en.wikipedia.org/wiki/Cold_seep"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:36.156842+00:00"
+instance: "kb-cron"
+---
+
+==== Discoveries ====
+The chemosynthetic communities of the Gulf of Mexico have been studied extensively since the 1990s, and communities first discovered on the upper slope are likely the best understood seep communities in the world. The history of the discovery of these remarkable animals has all occurred since the 1980s. Each major discovery was unexpected―from the first hydrothermal vent communities anywhere in the world to the first cold seep communities in the Gulf of Mexico.
+Communities were discovered in the eastern Gulf of Mexico in 1983 using the crewed submersible DSV Alvin, during a cruise investigating the bottom of the Florida Escarpment in areas of "cold" brine seepage, where they unexpectedly discovered tubeworms and mussels. Two groups fortuitously discovered chemosynthetic communities in the central Gulf of Mexico nearly concurrently in November and December 1984. During investigations in late December on the research vessel R/V Gyre cruise 84-G-12, by Texas A&M University, two bottom trawls were conducted to determine the effects of oil seepage on benthic ecology (until this investigation, all effects of oil seepage were assumed to be detrimental). Trawls unexpectedly recovered extensive collections of chemosynthetic organisms, including tubeworms and clams. a month earlier, LGL Ecological Research Associates was conducting a research cruise as part of the multiyear MMS Northern Gulf of Mexico Continental Slope Study  (Gallaway et al., 1988). Bottom photography as part of this project obtained images from the end of a film roll of a deep-sea camera sled (processed on board the vessel November 14, 1984) that resulted in clear images of vesicomyid clam chemosynthetic communities (Rossman et al., 1987) coincidentally in the same manner as the first documentation of chemosynthetic communities at the Galapagos Rift investigating hot water plumes by camera sled in the Pacific in 1976 (Lonsdale 1977). Photography during the same LGL/MMS cruise also documented tube-worm communities in situ in the Central Gulf of Mexico for the first time (not processed until after the cruise; Boland, 1986) prior to the initial submersible investigations and firsthand descriptions of Bush Hill (27°47′02″N 91°30′31″W) in 1986. The Bush Hill site was targeted by acoustic "wipeout" zones or lack of substrate structure caused by seeping hydrocarbons. This was determined using an acoustic pinger system during the same cruise on the R/V Edwin Link (renamed from Sea Diver and only 113 ft (34 m)), which used one of the Johnson Sea Link submersibles. This site represents the first eyes-on human observations of chemosynthetic communities in the northern Gulf of Mexico and is characterized by dense tubeworm and mussel accumulations, as well as exposed carbonate outcrops with numerous gorgonian and Lophelia coral colonies. Bush Hill has become one of the most thoroughly-studied chemosynthetic sites in the world.
+
+==== Distribution ====
+
+There is a clear relationship between known hydrocarbon discoveries at great depth in the Gulf slope and chemosynthetic communities, hydrocarbon seepage, and authigenic minerals including carbonates at the seafloor. While the hydrocarbon reservoirs are broad areas several kilometers beneath the Gulf, chemosynthetic communities occur in isolated areas with thin veneers of sediment only a few meters thick.
+The northern Gulf of Mexico slope includes a stratigraphic section more than 10 km (6.2 mi) thick and has been profoundly influenced by salt movement. Mesozoic source rocks from Upper Jurassic to Upper Cretaceous generate oil in most of the Gulf slope fields. Migration conduits supply fresh hydrocarbon materials through a vertical scale of 6–8 km (3.7–5.0 mi) toward the surface. The surface expressions of hydrocarbon migration are called seeps. Geological evidence demonstrates that hydrocarbon and brine seepage persists in spatially discrete areas for thousands of years.
+The time scale for oil and gas migration from source systems is on the scale of millions of years (Sassen, 1997). Seepage from hydrocarbon sources through faults towards the surface tends to be diffused through the overlying sediment, carbonate outcroppings, and hydrate deposits, so the corresponding hydrocarbon seep communities tend to be larger (a few hundred meters wide) than chemosynthetic communities found around the hydrothermal vents of the Eastern Pacific (MacDonald, 1992). There are large differences in the concentrations of hydrocarbons at seep sites. Roberts (2001) presented a spectrum of responses to be expected under a variety of flux rate conditions varying from very slow seepage to rapid venting. Very-slow-seepage sites do not support complex chemosynthetic communities; rather, they usually only support simple microbial mats (Beggiatoa sp.).
+In the upper slope environment, the hard substrates resulting from carbonate precipitation can have associated communities of non-chemosynthetic animals, including a variety of sessile cnidarians such as corals and sea anemones. At the rapid flux end of the spectrum, fluidized sediment generally accompanies hydrocarbons and formation fluids arriving at the seafloor. Mud volcanoes and mud flows result. Somewhere between these two end members exists the conditions that support densely populated and diverse communities of chemosynthetic organisms (microbial mats, siboglinid tube worms, bathymodioline mussels, lucinid and vesicomyid clams, and associated organisms). These areas are frequently associated with surface or near-surface gas hydrate deposits. They also have localized areas of lithified seafloor, generally authigenic carbonates but sometimes more exotic minerals such as barite are present.

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+title: "Cold seep"
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+---
+
+The widespread nature of Gulf of Mexico chemosynthetic communities was first documented during contracted investigations by the Geological and Environmental Research Group (GERG) of Texas A&M University for the Offshore Operators Committee. This survey remains the most widespread and comprehensive, although numerous additional communities have been documented since that time. Industry exploration for energy reserves in the Gulf of Mexico has also documented numerous new communities through a wide range of depths, including the deepest-known occurrence in the Central Gulf of Mexico in Alaminos Canyon Block 818 at a depth of 2,750 metres (9,020 feet). The occurrence of chemosynthetic organisms dependent on hydrocarbon seepage has been documented in water depths as shallow as 290 metres (950 feet) and as deep as 2,744 metres (9,003 feet). This depth range specifically places chemosynthetic communities in the deepwater region of the Gulf of Mexico, which is defined as water depths greater than 305 metres (1,001 feet).
+Chemosynthetic communities are not found on the continental shelf, although they do appear in the fossil record in water shallower than 200 metres (660 feet). One theory explaining this is that predation pressure has varied substantially over the time period involved (Callender and Powell 1999). More than 50 communities are now known to exist in 43 Outer Continental Shelf (OCS) blocks. Although a systematic survey has not been done to identify all chemosynthetic communities in the Gulf of Mexico, there is evidence indicating that many more such communities may exist. The depth limits of discoveries probably reflect the limits of exploration (lack of submersibles capable of depths over 1,000 metres (3,300 feet)).
+MacDonald et al. (1993 and 1996) have analyzed remote-sensing images from space that reveal the presence of oil slicks across the north-central Gulf of Mexico. Results confirmed extensive natural oil seepage in the Gulf of Mexico, especially in water depths greater than 1,000 metres (3,300 feet). A total of 58 additional potential locations were documented where seafloor sources were capable of producing perennial oil slicks. Estimated seepage rates ranged from 4 bbl/d (0.64 m3/d) to 70 bbl/d (11 m3/d) compared to less than 0.1 bbl/d (0.016 m3/d) for ship discharges (both normalized for 1,000 mi2 (640,000 ac)). This evidence considerably increases the area where chemosynthetic communities dependent on hydrocarbon seepage may be expected.
+The densest aggregations of chemosynthetic organisms have been found at water depths of around 500 metres (1,600 feet) and deeper. The best known of these communities was named Bush Hill by the investigators who first described it. It is a surprisingly large and dense community of chemosynthetic tube worms and mussels at a site of natural petroleum and gas seepage over a salt diapir in Green Canyon Block 185. The seep site is a small knoll that rises about 40 metres (130 feet) above the surrounding seafloor in about 580-metre (1,900-foot) water depth.

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+title: "Cold seep"
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+---
+
+==== Stability ====
+According to Sassen (1997) the role of hydrates at chemosynthetic communities has been greatly underestimated. The biological alteration of frozen gas hydrates was first discovered during the MMS study entitled "Stability and Change in Gulf of Mexico Chemosynthetic Communities". It is hypothesized that the dynamics of hydrate alteration could play a major role as a mechanism for regulation of the release of hydrocarbon gases to fuel biogeochemical processes and could also play a substantial role in community stability. Recorded bottom-water temperature excursions of several degrees in some areas such as the Bush Hill site (4–5 °C at 500-metre (1,600-foot) depth) are believed to result in dissociation of hydrates, resulting in an increase in gas fluxes (MacDonald et al., 1994). Although not as destructive as the volcanism at vent sites of the mid-ocean ridges, the dynamics of shallow hydrate formation and movement will clearly affect sessile animals that form part of the seepage barrier. There is potential of a catastrophic event where an entire layer of shallow hydrate could break free of the bottom and considerably affect local communities of chemosynthetic fauna. At deeper depths (>1,000 metres (3,300 feet)), the bottom-water temperature is colder (by approximately 3 °C) and undergoes less fluctuation. The formation of more stable and probably-deeper hydrates influences the flux of light hydrocarbon gases to the sediment surface, thus influencing the surface morphology and characteristics of chemosynthetic communities. Within complex communities such as Bush Hill, petroleum seems less important than previously thought (MacDonald, 1998b).
+Through taphonomic studies (death assemblages of shells) and interpretation of seep assemblage composition from cores, Powell et al. (1998) reported that, overall, seep communities were persistent over periods of 500–1,000 years and probably throughout the entire Pleistocene. Some sites retained optimal habitat over geological time scales. Powell reported evidence of mussel and clam communities persisting in the same sites for 500–4,000 years. Powell also found that both the composition of species and trophic tiering of hydrocarbon seep communities tend to be fairly constant across time, with temporal variations only in numerical abundance. He found few cases in which the community type changed (from mussel to clam communities, for example) or had disappeared completely. Faunal succession was not observed. Surprisingly, when recovery occurred after a past destructive event, the same chemosynthetic species reoccupied a site. There was little evidence of catastrophic burial events, but two instances were found in mussel communities in Green Canyon Block 234. The most notable observation reported by Powell (1995) was the uniqueness of each chemosynthetic community site.
+Precipitation of authigenic carbonates and other geologic events will undoubtedly alter surface seepage patterns over periods of many years, although through direct observation, no changes in chemosynthetic fauna distribution or composition were observed at seven separate study sites (MacDonald et al., 1995). A slightly longer period (19 years) can be referenced in the case of Bush Hill, the first Central Gulf of Mexico community described in situ in 1986. No mass die-offs or large-scale shifts in faunal composition have been observed (with the exception of collections for scientific purposes) over the 19-year history of research at this site.
+All chemosynthetic communities are located in water depths beyond the effect of severe storms, including hurricanes, and there would have been no alteration of these communities caused from surface storms, including hurricanes.
+
+==== Biology ====

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+title: "Cold seep"
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+
+MacDonald et al. (1990) has described four general community types. These are communities dominated by Vestimentiferan tube worms (Lamellibrachia c.f. barhami and Escarpia spp.), mytilid mussels (Seep Mytilid Ia, Ib, and III, and others), vesicomyid clams (Vesicomya cordata and Calyptogena ponderosa), and infaunal lucinid or thyasirid clams (Lucinoma sp. or Thyasira sp.). Bacterial mats are present at all sites visited to date. These faunal groups tend to display distinctive characteristics in terms of how they aggregate, the size of aggregations, the geological and chemical properties of the habitats in which they occur, and, to some degree, the heterotrophic fauna that occur with them. Many of the species found at these cold seep communities in the Gulf of Mexico are new to science and remain undescribed.
+Individual lamellibrachid tube worms, the longer of two taxa found at seeps, can reach lengths of 3 metres (9.8 feet) and live hundreds of years (Fisher et al., 1997; Bergquist et al., 2000). Growth rates determined from recovered marked tube worms have been variable, ranging from no growth of 13 individuals measured one year to a maximum growth of 9.6 cm/yr (3.8 in/yr) in a Lamellibrachia individual (MacDonald, 2002). Average growth rate was 2.19 cm/yr (0.86 in/yr) for the Escarpia-like species and 2.92 cm/yr (1.15 in/yr) for lamellibrachids. These are slower growth rates than those of their hydrothermal vent relatives, but Lamellibrachia individuals can reach lengths 2–3 times that of the largest known hydrothermal vent species. Individuals of Lamellibrachia sp. in excess of 3 metres (9.8 feet) have been collected on several occasions, representing probable ages in excess of 400 years (Fisher, 1995). Vestimentiferan tube worm spawning is not seasonal, and recruitment is episodic.
+Tubeworms are either male or female. One recent discovery indicates that the spawning of female Lamellibrachia appears to have produced a unique association with the large bivalve Acesta bullisi, which lives permanently attached to the anterior tube opening of the tubeworm, and feeds on the periodic egg release (Järnegren et al., 2005). This close association between the bivalves and tubeworms was discovered in 1984 (Boland, 1986) but not fully explained. Virtually all mature Acesta individuals are found on female rather than male tubeworms. This evidence and other experiments by Järnegren et al. (2005) seem to have solved this mystery.
+Growth rates for methanotrophic mussels at cold seep sites have been reported (Fisher, 1995). General growth rates were found to be relatively high. Adult mussel growth rates were similar to mussels from a littoral environment at similar temperatures. Fisher also found that juvenile mussels at hydrocarbon seeps initially grow rapidly, but the growth rate drops markedly in adults; they grow to reproductive size very quickly. Both individuals and communities appear to be very long-lived. These methane-dependent mussels have strict chemical requirements that tie them to areas of the most active seepage in the Gulf of Mexico. As a result of their rapid growth rates, mussel recolonization of a disturbed seep site could occur relatively rapidly. There is some evidence that mussels also have some requirement of a hard substrate and could increase in numbers if suitable substrate is increased on the seafloor (Fisher, 1995). Two associated species are always found associated with mussel beds—the gastropod Bathynerita naticoidea and a small Alvinocarid shrimp—suggesting these endemic species have excellent dispersal abilities and can tolerate a wide range of conditions (MacDonald, 2002).
+Unlike mussel beds, chemosynthetic clam beds may persist as a visual surface phenomenon for an extended period without input of new living individuals because of low dissolution rates and low sedimentation rates. Most clam beds investigated by Powell (1995) were inactive. Living individuals were rarely encountered. Powell reported that over a 50-year timespan, local extinctions and recolonization should be gradual and exceedingly rare. Contrasting these inactive beds, the first community discovered in the Central Gulf of Mexico consisted of numerous actively-plowing clams. The images obtained of this community were used to develop length/frequency and live/dead ratios as well as spatial patterns (Rosman et al., 1987a).
+Extensive bacterial mats of free-living bacteria are also evident at all hydrocarbon seep sites. These bacteria may compete with the major fauna for sulfide and methane energy sources and may also contribute substantially to overall production (MacDonald, 1998b). The white, nonpigmented mats were found to be an autotrophic sulfur bacteria Beggiatoa species, and the orange mats possessed an unidentified non-chemosynthetic metabolism (MacDonald, 1998b).
+Heterotrophic species at seep sites are a mixture of species unique to seeps (particularly molluscs and crustacean invertebrates) and those that are a normal component from the surrounding environment. Carney (1993) first reported a potential imbalance that could occur as a result of chronic disruption. Because of sporadic recruitment patterns, predators could gain an advantage, resulting in exterminations in local populations of mussel beds. It is clear that seep systems do interact with the background fauna, but conflicting evidence remains as to what degree outright predation on some specific community components such as tubeworms occurs (MacDonald, 2002). The more surprising results from this recent work is why background species do not utilize seep production more than seems to be evident. In fact, seep-associated consumers such as galatheid crabs and nerite gastropods had isotopic signatures, indicating that their diets were a mixture of seep and background production. At some sites, endemic seep invertebrates that would have been expected to obtain much if not all their diet from seep production actually consumed as much as 50 percent of their diets from the background.
+
+=== In the Atlantic Ocean ===

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+title: "Cold seep"
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+
+Cold-seep communities in the western Atlantic Ocean have also been described from a few dives on mud volcanoes and diapirs between 1,000 and 5,000 m (3,300–16,400 ft) depth in the Barbados accretionary prism area and from the Blake Ridge diapir off North Carolina. More recently, seep communities have been discovered in the eastern Atlantic, on a giant pockmark cluster in the Gulf of Guinea near the Congo deep channel, and also on other pockmarks of the Congo margin, Gabon margin and Nigeria margin and in the Gulf of Cádiz.
+The occurrence of chemosymbiotic biota in the extensive mud volcano fields of the Gulf of Cádiz was first reported in 2003. The chemosymbiotic bivalves collected from the mud volcanoes of the Gulf of Cadiz were reviewed in 2011.
+Cold seeps are also known from the Northern Atlantic Ocean, even ranging into the Arctic Ocean, off Canada and Norway.
+Extensive faunal sampling has been conducted from 400 and 3,300 m (1,300–10,800 ft) in the Atlantic Equatorial Belt from the Gulf of Mexico to the Gulf of Guinea including the Barbados accretionary prism, the Blake Ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria margin during Census of Marine Life ChEss project. Of the 72 taxa identified at the species level, a total of 9 species or species complexes are identified as amphi-Atlantic.
+The Atlantic Equatorial Belt seep megafauna community structure is influenced primarily by depth rather than by geographic distance. The bivalves Bathymodiolinae (within Mytilidae) species or complexes of species are the most widespread in the Atlantic. The Bathymodiolus boomerang complex is found at the Florida escarpment site, the Blake Ridge diapir, the Barbados prism, and the Regab site of Congo. The Bathymodiolus childressi complex is also widely distributed along the Atlantic Equatorial Belt from the Gulf of Mexico across to the Nigerian Margin, although not on the Regab or Blake Ridge sites. The commensal polynoid Branchipolynoe seepensis is known from the Gulf of Mexico, Gulf of Guinea, and Barbados. Other species with distributions extending from the eastern to western Atlantic are: gastropod  Cordesia provannoides, the shrimp Alvinocaris muricola, the galatheids Munidopsis geyeri and Munidopsis livida, and probably the holothurid Chiridota hydrothermica.
+There have been found cold seeps also in the Amazon deepsea fan. High-resolution seismic profiles near the shelf edge show evidence of near-surface slumps and faulting 20–50 m (66–164 ft) in the subsurface and concentrations (about 500 m2 or 5,400 ft2) of methane gas. Several studies (e.g., Amazon Shelf Study—AMASEDS, LEPLAC, REMAC, GLORIA, Ocean Drilling Program) indicate that there is evidence for gas seepage on the slope off the Amazon fan based on the incidence of bottom-simulating reflections (BSRs), mud volcanoes, pockmarks, gas in sediments, and deeper hydrocarbon occurrences. The existence of methane at relatively shallow depths and extensive areas of gas hydrates have been mapped in this region. Also, gas chimneys have been reported, and exploratory wells have discovered sub-commercial gas accumulations and pockmarks along fault planes. A sound geological and geophysical understanding of the Foz do Amazonas Basin is already available and used by the energy companies.
+Exploration of new areas, such as potential seep sites off of the east coast of the U.S. and the Laurentian fan where chemosynthetic communities are known deeper than 3,500 m (11,500 ft), and shallower sites in the Gulf of Guinea are need to study in the future.

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+title: "Cold seep"
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+
+=== In the Mediterranean ===
+The first biological evidence for reduced environments in the Mediterranean Sea was the presence of Lucinidae and Vesicomyidae bivalve shells cored on the top of the Napoli mud volcano (33°43′52″N 24°40′52″E; "Napoli" is only a name of a seamount. It is located south of Crete), located at 1,900 m deep on the Mediterranean Ridge in the subduction zone of the African Plate. This was followed by the description of a new Lucinidae bivalve species, Lucinoma kazani, associated with bacterial endosymbionts. In the southeastern Mediterranean, communities of polychaetes and bivalves were also found associated with cold seeps and carbonates near Egypt and the Gaza Strip at depths of 500–800 m, but no living fauna was collected. The first in situ observations of extensive living chemosynthetic communities in the eastern Mediterranean Sea prompted cooperation between biologists, geochemists, and geologists. During submersible dives, communities comprising large fields of small bivalves (dead and alive), large siboglinid tube worms, isolated or forming dense aggregations, large sponges, and associated endemic fauna were observed in various cold seep habitats associated with carbonate crusts at 1,700–2,000 m depth. Two mud volcano fields were first explored, one along the Mediterranean Ridge, where most of them were partially (Napoli, Milano mud volcanoes) or totally (Urania, Maidstone mud volcanoes) affected by brines, and the other on the Anaximander mounds south of Turkey. The latter area includes the large Amsterdam mud volcano, which is affected by recent mudflows, and the smaller Kazan or Kula mud volcanoes. Gas hydrates have been sampled at the Amsterdam and Kazan mud volcanoes, and high methane levels have been recorded above the seafloor. Several provinces of the Nile deep-sea fan have been explored recently. These include the very active brine seepage named the Menes Caldera in the eastern province between 2,500 m and 3,000 m, the pockmarks in the central area along middle and lower slopes, and the mud volcanoes of the eastern province, as well as one in the central upper slope (North Alex area) at 500 m depth.
+During these first exploratory dives, symbiont-bearing taxa that are similar to those observed on the Olimpi and Anaximander mud fields were sampled and identified. This similarity is not surprising, as most of these taxa were originally described from dredging in the Nile fan. Up to five species of bivalves harboring bacterial symbionts colonized these methane- and sulfide-rich environments. A new species of Siboglinidae polychaete, Lamellibrachia anaximandri, the tubeworm colonizing cold seeps from the Mediterranean ridge to the Nile deep-sea fan, has just been described in 2010. Moreover, the study of symbioses revealed associations with chemoautotrophic bacteria, sulfur oxidizers in Vesicomyidae and Lucinidae bivalves and Siboglinidae tubeworms, and highlighted the exceptional diversity of bacteria living in symbiosis with small Mytilidae. The Mediterranean seeps appear to represent a rich habitat characterized by megafauna species richness (e.g., gastropods) or the exceptional size of some species such as sponges (Rhizaxinella pyrifera) and crabs (Chaceon mediterraneus), compared with their background counterparts. This contrasts with the low macro- and mega-faunal abundance and diversity of the deep eastern Mediterranean. Seep communities in the Mediterranean that include endemic chemosynthetic species and associated fauna differ from the other known seep communities in the world at the species level but also by the absence of the large-size bivalve genera Calyptogena or Bathymodiolus. The isolation of the Mediterranean seeps from the Atlantic Ocean after the Messinian crisis led to the development of unique communities, which are likely to differ in composition and structure from those in the Atlantic Ocean. Further expeditions involved quantitative sampling of habitats in different areas, from the Mediterranean Ridge to the eastern Nile deep-sea fan. Cold seeps discovered in the Sea of Marmara in 2008 have also revealed chemosynthesis-based communities that showed a considerable similarity to the symbiont-bearing fauna of eastern Mediterranean cold seeps.
+
+=== In the Indian Ocean ===
+In the Makran Trench, a subduction zone along the northeastern margin of the Gulf of Oman adjacent to the southwestern coast of Pakistan and the southeastern coast of Iran, compression of an accretionary wedge has resulted in the formation of cold seeps and mud volcanoes.
+
+=== In the West Pacific ===
+Native aluminium has been reported also in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. (2011) have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)4− to metallic aluminium by bacteria.
+
+==== Japan ====
+
+Deep sea communities around Japan are mainly researched by Japan Agency for Marine-Earth Science and Technology (JAMSTEC). DSV Shinkai 6500, Kaikō, and other groups have discovered many sites.
+Methane seep communities in Japan are distributed along plate convergence areas because of the accompanying tectonic activity. Many seeps have been found in the Japan Trench, Nankai Trough, Ryukyu Trench, Sagami Bay, Suruga Bay, and the Sea of Japan.
+Members of cold seep communities are similar to other regions in terms of family or genus, such as Polycheata, Lamellibrachia, Bivalavia, Solemyidae, Bathymodiolus in Mytilidae, Thyasiridae, Calyptogena in Vesicomyidae, and so forth. Many of the species in Japan's cold seeps are endemic.
+In Kagoshima Bay, there are methane gas seepages called "tagiri" (boiling). Lamellibrachia satsuma live around there. The depth of this site is only 80 m, which is the shallowest point where Siboglinidae are known to live. L. satsuma may be kept in an aquarium for a long period at 1 atm. Two aquariums in Japan are keeping and displaying L. satsuma. An observation method to introduce it into a transparent vinyl tube is being developed.
+
+DSV Shinkai 6500 discovered vesicomyid clam communities in the Southern Mariana Forearc. They depend on methane, which originates in serpentinite. Other chemosynthetic communities would depend on hydrocarbon origins organic substance in crust, but these communities depend on methane originating from inorganic substances from the mantle.
+In 2011, the area around the Japan Trench suffered from the Tōhoku earthquake. There are cracks, methane seepages, and bacterial mats which were probably created by the earthquake.

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+---
+title: "Cold seep"
+chunk: 9/10
+source: "https://en.wikipedia.org/wiki/Cold_seep"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:36.156842+00:00"
+instance: "kb-cron"
+---
+
+==== New Zealand ====
+Off the mainland coast of New Zealand, shelf-edge instability is enhanced in some locations by cold seeps of methane-rich fluids that likewise support chemosynthetic faunas and carbonate concretions. Dominant animals are tubeworms of the family Siboglinidae and bivalves of families Vesicomyidae and Mytilidae (Bathymodiolus). Many of its species appear to be endemic. Deep bottom trawling has severely damaged cold seep communities, and those ecosystems are threatened. Cold seeps are found at depths down to 2,000 m, and the topographic and chemical complexity of the habitats are not yet mapped. The scale of new-species discovery in these poorly-studied or unexplored ecosystems is likely to be high.
+
+=== In the East Pacific ===
+
+In the deep sea, the COMARGE project has studied the biodiversity patterns along and across the Chilean margin through a complexity of ecosystems such as methane seeps and oxygen minimum zones, reporting that such habitat heterogeneity may influence the biodiversity patterns of the local fauna. Seep fauna include bivalves of families Lucinidae, Thyasiridae, Solemyidae (Acharax sp.), and Vesicomyidae (Calyptogena gallardoi) and polychaetes (Lamellibrachia sp. and two other polychaete species). Furthermore, in these soft reduced sediments below the oxygen minimum zone off the Chilean margin, a diverse microbial community composed by a variety of large prokaryotes (mainly large multi-cellular filamentous "mega bacteria" of the genera Thioploca and Beggiatoa, and of "macrobacteria" including a diversity of phenotypes), protists (ciliates, flagellates, and foraminifers), as well as small metazoans (mostly nematodes and polychaetes) has been found. Gallardo et al. (2007) argue that the likely chemolithotrophic metabolism of most of these mega- and macrobacteria offer an alternative explanation to fossil findings, in particular to those from obvious non-littoral origins, suggesting that traditional hypotheses on the cyanobacterial origin of some fossils may have to be revised.
+Cold seeps (pockmarks) are also known from depths of 130 m in the Hecate Strait, British Columbia, Canada. Unobvious fauna (also unobvious for cold seeps) have been found there with these dominating species: sea snail Fusitriton oregonensis, anemone Metridium giganteum, encrusting sponges, and bivalve Solemya reidi.
+Cold seeps with chemosynthetic communities along the USA Pacific coast occur in Monterey Canyon, just off Monterey Bay, California on a mud volcano. There have been found, for example, Calyptogena clams Calyptogena kilmeri and Calyptogena pacifica and foraminiferan Spiroplectammina biformis.
+
+map of cold seeps in the Monterey Bay
+Additionally, seeps have been discovered offshore southern California in the inner California Borderlands along several fault systems including the San Clemente fault, San Pedro fault, and San Diego Trough fault. Fluid flow at the seeps along the San Pedro and San Diego Trough faults appears controlled by localized restraining bends in the faults.
+
+=== In the Antarctic ===
+The first cold seep from the Southern Ocean was reported in 2005. The relatively few investigations to the Antarctic deep sea have shown the presence of deep-water habitats, including hydrothermal vents, cold seeps, and mud volcanoes. Other than the Antarctic Benthic Deep-Sea Biodiversity Project (ANDEEP) cruises, little work has been done in the deep sea. There are more species waiting to be described.
+
+== Detection ==
+With continuing experience, particularly on the upper continental slope in the Gulf of Mexico, the successful prediction of the presence of tubeworm communities continues to improve; however, chemosynthetic communities cannot be reliably detected directly using geophysical techniques. Hydrocarbon seeps that allow chemosynthetic communities (Guaymas Basin) to exist do modify the geological characteristics in ways that can be remotely detected, but the time scales of co-occurring active seepage and the presence of living communities is always uncertain. These known sediment modifications include (1) precipitation of authigenic carbonate in the form of micronodules, nodules, or rock masses; (2) formation of gas hydrates; (3) modification of sediment composition through concentration of hard chemosynthetic organism remains (such as shell fragments and layers); (4) formation of interstitial gas bubbles or hydrocarbons; and (5) formation of depressions or pockmarks by gas expulsion. These features give rise to acoustic effects such as wipeout zones (no echoes), hard bottoms (strongly reflective echoes), bright spots (reflection enhanced layers), or reverberant layers (Behrens, 1988; Roberts and Neurauter, 1990). Potential locations for most types of communities can be determined by careful interpretation of these various geophysical modifications, but to date, the process remains imperfect and confirmation of living communities requires direct visual techniques.
+
+== Fossilized records ==
+
+Cold seep deposits are found throughout the Phanerozoic geologic record, especially in the Late Mesozoic and Cenozoic. Notable examples can be found in the Permian of Tibet, the Cretaceous of Colorado and Hokkaido, the Palaeogene of Honshu, the Neogene of Northern Italy, and the Pleistocene of California. These fossil cold seeps are characterized by mound-like topography (where preserved), coarsely crystalline carbonates, and abundant mollusks and brachiopods.

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+---
+title: "Cold seep"
+chunk: 10/10
+source: "https://en.wikipedia.org/wiki/Cold_seep"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:36.156842+00:00"
+instance: "kb-cron"
+---
+
+== Environmental impacts ==
+Major threats that cold seep ecosystems and their communities face today are seafloor litter, chemical contaminants, and climate change. Seafloor litter alters the habitat by providing hard substrate where none was available before or by overlying the sediment, thereby inhibiting gas exchange and interfering with organisms on the bottom of the sea. Studies of marine litter in the Mediterranean include surveys of seabed debris on the continental shelf, slope, and bathyal plain. In most studies, plastic items accounted for much of the debris, sometimes as much as 90% or more of the total, owing to their ubiquitous use and poor degradability.
+Weapons and bombs have also been discarded at sea, and their dumping in open waters contributes to seafloor contamination. Another major threat to the benthic fauna is the presence of lost fishing gear, such as nets and longlines, which contribute to ghost fishing and can damage fragile ecosystems such as cold-water corals.
+Chemical contaminants such as persistent organic pollutants, toxic metals (e.g., Hg, Cd, Pb, Ni), radioactive compounds, pesticides, herbicides, and pharmaceuticals are also accumulating in deep-sea sediments. Topography (such as canyons) and hydrography (such as cascading events) play a major role in the transportation and accumulation of these chemicals from the coast and shelf to the deep basins, affecting the local fauna. Recent studies have detected the presence of significant levels of dioxins in the commercial shrimp Aristeus antennatus  and significant levels of persistent organic pollutants in mesopelagic and bathypelagic cephalopods.
+Climate-driven processes and climate change will affect the frequency and intensity of cascading, with unknown effects on the benthic fauna. Another potential effect of climate change is related to energy transport from surface waters to the seafloor. Primary production will change in the surface layers according to sun exposure, water temperature, major stratification of water masses, and other effects, and this will affect the food chain down to the deep seafloor, which will be subject to differences in quantity, quality, and timing of organic matter input. As commercial fisheries move into deeper waters, all of these effects will affect the communities and populations of organisms in cold seeps and the deep sea in general.
+
+== See also ==
+
+Chemotroph
+Gas emission crater
+Gas hydrate pingo
+Guaymas Basin
+
+== References ==
+This article incorporates a public domain work of the United States Government from references and CC-BY-2.5 from references and CC-BY-3.0 text from the reference
+
+== Further reading ==
+Bright, M.; Plum, C.; Riavitz, L. A.; Nikolov, N.; Martínez Arbizu, P.; Cordes, E. E.; Gollner, S. (2010). "Epizooic metazoan meiobenthos associated with tubeworm and mussel aggregations from cold seeps of the Northern Gulf of Mexico". Deep-Sea Research Part II: Topical Studies in Oceanography. 57 (21–23): 1982–1989. Bibcode:2010DSRII..57.1982B. doi:10.1016/j.dsr2.2010.05.003. PMC 2995211. PMID 21264038.
+German, C. R.; Ramirez-Llodra, E.; Baker, M. C.; Tyler, P. A.; the ChEss Scientific Steering Committee (2011). "Deep-Water Chemosynthetic Ecosystem Research during the Census of Marine Life Decade and Beyond: A Proposed Deep-Ocean Road Map". PLoS ONE. 6 (8) e23259. Bibcode:2011PLoSO...623259G. doi:10.1371/journal.pone.0023259. PMC 3150416. PMID 21829722.
+Lloyd, K. G.; Albert, D. B.; Biddle, J. F.; Chanton, J. P.; Pizarro, O.; Teske, A. (2010). "Spatial Structure and Activity of Sedimentary Microbial Communities Underlying a Beggiatoa spp. Mat in a Gulf of Mexico Hydrocarbon Seep". PLoS ONE. 5 (1) e8738. Bibcode:2010PLoSO...5.8738L. doi:10.1371/journal.pone.0008738. PMC 2806916. PMID 20090951.
+Metaxas, A.; Kelly, N. E. (2010). "Do Larval Supply and Recruitment Vary among Chemosynthetic Environments of the Deep Sea?". PLoS ONE. 5 (7) e11646. Bibcode:2010PLoSO...511646M. doi:10.1371/journal.pone.0011646. PMC 2906503. PMID 20657831.
+Rodríguez, E.; Daly, M. (2010). "Phylogenetic Relationships among Deep-Sea and Chemosynthetic Sea Anemones: Actinoscyphiidae and Actinostolidae (Actiniaria: Mesomyaria)". PLoS ONE. 5 (6) e10958. Bibcode:2010PLoSO...510958R. doi:10.1371/journal.pone.0010958. PMC 2881040. PMID 20532040.
+Sibuet, M.; Olu, K. (1998). "Biogeography, biodiversity and fluid dependence of deep-sea cold-seep communities at active and passive margins". Deep-Sea Research Part II: Topical Studies in Oceanography. 45 (1–3): 517–567. Bibcode:1998DSRII..45..517S. doi:10.1016/S0967-0645(97)00074-X.
+Vinn, O.; Hryniewicz, K; Little, C.T.S.; Nakrem, H.A. (2014). "A Boreal serpulid fauna from Volgian-Ryazanian (latest Jurassic-earliest Cretaceous) shelf sediments and hydrocarbon seeps from Svalbard". Geodiversitas. 36 (4): 527–540. doi:10.5252/g2014n4a2. S2CID 129587761. Retrieved 9 January 2014.
+Vinn, O.; Kupriyanova, E.K.; Kiel, S. (2013). "Serpulids (Annelida, Polychaeta) at Cretaceous to modern hydrocarbon seeps: Ecological and evolutionary patterns". Palaeogeography, Palaeoclimatology, Palaeoecology. 390: 35–41. Bibcode:2013PPP...390...35V. doi:10.1016/j.palaeo.2012.08.003. Retrieved 9 January 2014.
+
+== External links ==
+
+Paul Yancy's vents and seeps page
+Monterey Bay Aquarium Research Institute's seeps page
+ScienceDaily News: Tubeworms in deep sea discovered to have record long life spans

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+---
+title: "Continental margin"
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:37.444285+00:00"
+instance: "kb-cron"
+---
+
+A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. The continental margin consists of three different features: the continental rise, the continental slope, and the continental shelf. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. Continental margins constitute about 28% of the oceanic area.
+
+
+== Subzones ==
+ 
+The continental shelf is the relatively shallow water area found in proximity to continents; it is the portion of the continental margin that transitions from the shore out towards the ocean. Continental shelves are believed to make up 7% of the sea floor. The width of continental shelves worldwide varies in the range of 0.03–1500 km. The continental shelf is generally flat, and ends at the shelf break, where there is a drastic increase in slope angle: The mean angle of continental shelves worldwide is 0° 07′, and typically steeper closer to the coastline than it is near the shelf break. 
+At the shelf break begins the continental slope, which can be 1–5 km above the deep-ocean floor. The continental slope often exhibits features called submarine canyons. Submarine canyons often cut into the continental shelves deeply, with near-vertical sides, and continue to cut the morphology to the abyssal plain. 
+These canyons are often V-shaped and can sometimes enlarge onto the continental shelf. At the base of the continental slope, there is a sudden decrease in slope angle, and the sea floor begins to level out towards the abyssal plain. This portion of the seafloor is called the continental rise, and marks the outermost zone of the continental margin.
+
+
+== Types ==
+There are two types of continental margins: active and passive margins.
+Active margins are typically associated with lithospheric plate boundaries. These active margins can be convergent or transform margins, and are also places of high tectonic activity, including volcanoes and earthquakes. The West Coast of North America and South America are active margins. Active continental margins are typically narrow from coast to shelf break, with steep descents into trenches. Convergent active margins occur where oceanic plates meet continental plates. The denser oceanic crust of one plate subducts below the less dense continental crust of another plate. Convergent active margins are the most common type of active margin. Transform active margins are rarer and occur when an oceanic plate and a continental plate are moving parallel to each other in opposite directions. These transform margins are often characterized by many offshore faults, which causes a high degree of relief offshore, marked by islands, shallow banks, and deep basins. This is known as the continental borderland.
+Passive margins are often located in the interior of lithospheric plates, away from the plate boundaries, and lack major tectonic activity. They often face mid-ocean ridges. From this comes a wide variety of features, such as low-relief land extending miles away from the beach, long river systems, and piles of sediment accumulating on the continental shelf. The East Coast of the United States is an example of a passive margin. These margins are much wider and less steep than active margins.
+
+
+== Sediment accumulation ==
+
+As continental crust weathers and erodes, it degrades into mainly sands and clays. Many of these particles end up in streams and rivers that then dump into the ocean. Of all the sediment in the stream load, 80% is then trapped and dispersed on continental margins. While modern river sediment is often still preserved closer to shore, continental shelves show high levels of glacial and relict sediments, deposited when sea level was lower. Often found on passive margins are several kilometres of sediment, consisting of terrigenous and carbonate (biogenous) deposits. These sediment reservoirs are often useful in the study of paleoceanography and the original formation of ocean basins. These deposits are often not well preserved on active margin shelves due to tectonic activity.
+
+
+== Economic significance ==
+The continental shelf is the most economically valuable part of the ocean. It often is the most productive portion of the continental margin, as well as the most studied portion, due to its relatively shallow, accessible depths.
+Due to the rise of offshore drilling, mining, and the limitations of fisheries off the continental shelf, the United Nations Convention on the Law of the Sea (UNCLOS) was established. The edge of the continental margin is one criterion for the boundary of the internationally recognized claims to underwater resources by countries in the definition of the "continental shelf" by the UNCLOS (although in the UN definition the "legal continental shelf" may extend beyond the geomorphological continental shelf and vice versa). Such resources include fishing grounds, oil and gas accumulations, sand, gravel, and some heavy minerals in the shallower areas of the margin. Metallic mineral resources are thought to also be associated with certain active margins, and of great value.
+
+
+== See also ==
+Continent-ocean boundary
+Convergent boundary
+Passive margin
+
+
+== References ==
+
+
+== External links ==
+Map showing the locations of active and passive continental margins and the eight ocean regions

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+---
+title: "Continental shelf"
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+category: "reference"
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+date_saved: "2026-05-05T07:34:38.658115+00:00"
+instance: "kb-cron"
+---
+
+A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an "insular shelf."
+The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope, surrounded by the flatter continental rise, in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise's gradient is intermediate between the gradients of the slope and the shelf.
+Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores of a particular country to which it belongs.
+
+== Topography ==
+The shelf usually ends at a point of increasing slope (called the shelf break). The sea floor below the break is the continental slope. Below the slope is the continental rise, which finally merges into the deep ocean floor, the abyssal plain. The continental shelf and the slope are part of the continental margin.
+
+ 	
+The shelf area is commonly subdivided into the inner continental shelf, mid continental shelf, and outer continental shelf, each with their specific geomorphology and marine biology.
+The character of the shelf changes dramatically at the shelf break, where the continental slope begins. With a few exceptions, the shelf break is located at a remarkably uniform depth of roughly 140 m (460 ft); this is likely a hallmark of past ice ages, when sea level was lower than it is now.
+The continental slope is much steeper than the shelf; the average angle is 3°, but it can be as low as 1° or as high as 10°. The slope is often cut with submarine canyons. The physical mechanisms involved in forming these canyons were not well understood until the 1960s.
+
+== Geographical distribution ==
+
+ 
+Continental shelves cover an area of about 27 million km2 (10 million sq mi), equal to about 7% of the surface area of the oceans. The width of the continental shelf varies considerably—it is not uncommon for an area to have virtually no shelf at all, particularly where the forward edge of an advancing oceanic plate dives beneath continental crust in an offshore subduction zone such as off the coast of Chile or the west coast of Sumatra. 
+The largest shelf—the Siberian Shelf in the Arctic Ocean—stretches to 1,500 kilometers (930 mi) in width. The South China Sea lies over another extensive area of continental shelf, the Sunda Shelf, which joins Borneo, Sumatra, and Java to the Asian mainland. Other familiar bodies of water that overlie continental shelves are the North Sea and the Persian Gulf. The average width of continental shelves is about 80 km (50 mi). The depth of the shelf also varies, but is generally limited to water shallower than 100 m (330 ft).  The slope of the shelf is usually quite low, on the order of 0.5°; vertical relief is also minimal, at less than 20 m (66 ft).
+Though the continental shelf is treated as a physiographic province of the ocean, it is not part of the deep ocean basin proper, but the flooded margins of the continent. Passive continental margins such as most of the Atlantic coasts have wide and shallow shelves, made of thick sedimentary wedges derived from long erosion of a neighboring continent. Active continental margins have narrow, relatively steep shelves, due to frequent earthquakes that move sediment to the deep sea.
+
+== Sediments ==
+The continental shelves are covered by terrigenous sediments; that is, those derived from erosion of the continents. However, little of the sediment is from current rivers; some 60–70% of the sediment on the world's shelves is relict sediment, deposited during the last ice age, when sea level was 100–120 m lower than it is now.
+Sediments usually become increasingly fine with distance from the coast; sand is limited to shallow, wave-agitated waters, while silt and clays are deposited in quieter, deep water far offshore.  These accumulate 15–40 centimetres (5.9–15.7 in) every millennium, much faster than deep-sea pelagic sediments.
+
+== Shelf seas ==
+"Shelf seas" are the ocean waters on the continental shelf. Their motion is controlled by the combined influences of the tides, wind-forcing and brackish water formed from river inflows (Regions of Freshwater Influence). These regions can often be biologically highly productive due to mixing caused by the shallower waters and the enhanced current speeds. Despite covering only about 8% of Earth's ocean surface area, shelf seas support 15–20% of global primary productivity.
+In temperate continental shelf seas, three distinctive oceanographic regimes are found, as a consequence of the interplay between surface heating, lateral buoyancy gradients (due to river inflow), and turbulent mixing by the tides and to a lesser extent the wind.

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+title: "Continental shelf"
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+category: "reference"
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+date_saved: "2026-05-05T07:34:38.658115+00:00"
+instance: "kb-cron"
+---
+
+In shallower water with stronger tides and away from river mouths, tidal turbulence overcomes the stratifying influence of surface heating, and the water column remains well mixed for the entire seasonal cycle.
+In contrast, in deeper water, the surface heating wins out in summer, to produce seasonal stratification with a warm surface layer overlying the isolated deep water.
+(The well mixed and seasonally stratifying regimes are separated by persistent features called tidal mixing fronts.)
+A third regime which links estuaries to shelf seas, Regions of Freshwater Influence (ROFIs), is found where estuaries enter shelf seas, for example in the Liverpool Bay area of the Irish Sea and Rhine Outflow region of the North Sea. Here, stratification can vary on timescales from the semidiurnal tidal cycle through to the springs-neap tidal cycle due to a process known as "tidal straining". While the North Sea and Irish Sea are two of the better studied shelf seas, they are not necessarily representative of all shelf seas as there is a wide variety of behaviours to be found:
+Indian Ocean shelf seas are dominated by major river systems, including the Ganges and Indus rivers. The shelf seas around New Zealand are complicated because the submerged continent of Zealandia creates wide plateaus. Shelf seas around Antarctica and the shores of the Arctic Ocean are influenced by sea ice production and polynya.
+There is evidence that changing wind, rainfall, and regional ocean currents in a warming ocean are having an effect on some shelf seas. Improved data collection via Integrated Ocean Observing Systems in shelf sea regions is making identification of these changes possible.
+
+== Biota ==
+
+Continental shelves teem with life because of the sunlight available in shallow waters, in contrast to the biotic desert of the oceans' abyssal plain. The pelagic (water column) environment of the continental shelf constitutes the neritic zone, and the benthic (sea floor) province of the shelf is the sublittoral zone. The shelves make up less than 10% of the ocean, and a rough estimate suggests that only about 30% of the continental shelf sea floor receives enough sunlight to allow benthic photosynthesis.
+Though the shelves are usually fertile, if anoxic conditions prevail during sedimentation, the deposits may over geologic time become sources for fossil fuels.
+
+== Economic significance ==
+
+The continental shelf is the best understood part of the ocean floor, as it is relatively accessible. Most commercial exploitation of the sea, such as offshore drilling, extraction of metallic ore, non-metallic ore, and hydrocarbons, takes place on the continental shelf.
+Sovereign rights over their continental shelves down to a depth of 100 m (330 ft) or to a distance where the depth of waters admitted of resource exploitation were claimed by the marine nations that signed the Convention on the Continental Shelf drawn up by the UN's International Law Commission in 1958. This was partly superseded by the 1982 United Nations Convention on the Law of the Sea (UNCLOS). The 1982 convention created the 200 nautical miles (370 km; 230 mi) exclusive economic zone, plus continental shelf rights for states with physical continental shelves that extend beyond that distance.
+The legal definition of a continental shelf differs significantly from the geological definition. UNCLOS states that the shelf extends to the limit of the continental margin, but no less than 200 nmi (370 km; 230 mi) and no more than 350 nmi (650 km; 400 mi) from the baseline. Thus inhabited volcanic islands such as the Canaries, which have no actual continental shelf, nonetheless have a legal continental shelf, whereas uninhabitable islands have no shelf.
+
+== See also ==
+
+Baseline
+Continental island
+Continental shelf of Brazil
+Continental shelf pump
+Exclusive economic zone
+International waters
+Land bridge
+Outer Continental Shelf
+Passive margin
+Region of freshwater influence
+Territorial waters
+
+== Notes ==

data/en.wikipedia.org/wiki/Continental_shelf-2.md

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+---
+title: "Continental shelf"
+chunk: 3/3
+source: "https://en.wikipedia.org/wiki/Continental_shelf"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:38.658115+00:00"
+instance: "kb-cron"
+---
+
+== References ==
+Atkinson, Larry P.; Lee, Thomas N.; Blanton, Jackson O.; Chandler, William S. (30 May 1983). "Climatology of the southeastern United States continental shelf waters". Journal of Geophysical Research: Oceans. 88 (C8): 4705–4718. Bibcode:1983JGR....88.4705A. doi:10.1029/JC088iC08p04705.
+de Haas, Henk; van Weering, Tjeerd C.E; de Stigter, Henko (March 2002). "Organic carbon in shelf seas: sinks or sources, processes and products". Continental Shelf Research. 22 (5): 691–717. Bibcode:2002CSR....22..691D. doi:10.1016/S0278-4343(01)00093-0.
+"shelf break – geology". Encyclopædia Britannica.
+Figueiredo, Alberto Garcia; Pacheco, Carlos Eduardo Pereira; de Vasconcelos, Sérgio Cadena; da Silva, Fabiano Tavares (2016). "Continental Shelf Geomorphology and Sedimentology". Geology and Geomorphology: 13–31. doi:10.1016/B978-85-352-8444-7.50009-3. ISBN 9788535284447.
+Gattuso, Jean-Pierre; Gentili, B.; Duarte, C. M.; Kleypas, J. A.; Middelburg, J. J.; Antoine, D. (2006). "Light availability in the coastal ocean: impact on the distribution of benthic photosynthetic organisms and their contribution to primary production". Biogeosciences. 3 (4). European Geosciences Union: 489–513. Bibcode:2006BGeo....3..489G. doi:10.5194/bg-3-489-2006. hdl:20.500.11937/23744. S2CID 13715554. hal-00330315. Retrieved 1 July 2021.
+Gross, M. Grant (1972). Oceanography: A View of the Earth. Englewood Cliffs: Prentice-Hall. ISBN 978-0-13-629659-1. Retrieved 12 January 2016.
+Guihou, K.; Polton, J.; Harle, J.; Wakelin, S.; O'Dea, E.; Holt, J. (January 2018). "Kilometric Scale Modeling of the North West European Shelf Seas: Exploring the Spatial and Temporal Variability of Internal Tides: Modeling of the Atlantic European Shelf". Journal of Geophysical Research: Oceans. 123 (1): 688–707. doi:10.1002/2017JC012960. hdl:11336/100068.
+Han, Weiqing; McCreary, Julian P. (15 January 2001). "Modeling salinity distributions in the Indian Ocean". Journal of Geophysical Research: Oceans. 106 (C1): 859–877. Bibcode:2001JGR...106..859H. doi:10.1029/2000JC000316.
+Harris, P.T.; Macmillan-Lawler, M.; Rupp, J.; Baker, E.K. (June 2014). "Geomorphology of the oceans". Marine Geology. 352: 4–24. Bibcode:2014MGeol.352....4H. doi:10.1016/j.margeo.2014.01.011.
+Jackson, Julia A., ed. (1997). Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN 0922152349.
+Montero-Serra, Ignasi; Edwards, Martin; Genner, Martin J. (January 2015). "Warming shelf seas drive the subtropicalization of European pelagic fish communities". Global Change Biology. 21 (1): 144–153. Bibcode:2015GCBio..21..144M. doi:10.1111/gcb.12747. PMID 25230844. S2CID 25834528.
+Morley, Simon A.; Barnes, David K. A.; Dunn, Michael J. (17 January 2019). "Predicting Which Species Succeed in Climate-Forced Polar Seas". Frontiers in Marine Science. 5: 507. Bibcode:2019FrMaS...5..507M. doi:10.3389/fmars.2018.00507.
+Muelbert, José H.; Acha, Marcelo; Mianzan, Hermes; Guerrero, Raúl; Reta, Raúl; Braga, Elisabete S.; Garcia, Virginia M.T.; Berasategui, Alejandro; Gomez-Erache, Mónica; Ramírez, Fernando (July 2008). "Biological, physical and chemical properties at the Subtropical Shelf Front Zone in the SW Atlantic Continental Shelf". Continental Shelf Research. 28 (13): 1662–1673. Bibcode:2008CSR....28.1662M. doi:10.1016/j.csr.2007.08.011.
+O’Callaghan, Joanne; Stevens, Craig; Roughan, Moninya; Cornelisen, Chris; Sutton, Philip; Garrett, Sally; Giorli, Giacomo; Smith, Robert O.; Currie, Kim I.; Suanda, Sutara H.; Williams, Michael; Bowen, Melissa; Fernandez, Denise; Vennell, Ross; Knight, Benjamin R.; Barter, Paul; McComb, Peter; Oliver, Megan; Livingston, Mary; Tellier, Pierre; Meissner, Anna; Brewer, Mike; Gall, Mark; Nodder, Scott D.; Decima, Moira; Souza, Joao; Forcén-Vazquez, Aitana; Gardiner, Sarah; Paul-Burke, Kura; Chiswell, Stephen; Roberts, Jim; Hayden, Barb; Biggs, Barry; Macdonald, Helen (26 March 2019). "Developing an Integrated Ocean Observing System for New Zealand". Frontiers in Marine Science. 6: 143. Bibcode:2019FrMaS...6..143O. doi:10.3389/fmars.2019.00143. hdl:10289/16618.
+Pinet, Paul R. (2003). Invitation to Oceanography. Boston: Jones & Bartlett Learning. ISBN 978-0-7637-2136-7. Retrieved 13 January 2016.
+Stevens, Craig L.; O’Callaghan, Joanne M.; Chiswell, Stephen M.; Hadfield, Mark G. (2 January 2021). "Physical oceanography of New Zealand/Aotearoa shelf seas – a review". New Zealand Journal of Marine and Freshwater Research. 55 (1): 6–45. Bibcode:2021NZJMF..55....6S. doi:10.1080/00288330.2019.1588746.
+Tyson, R. V.; Pearson, T. H. (1991). "Modern and ancient continental shelf anoxia: an overview". Geological Society, London, Special Publications. 58 (1): 1–24. Bibcode:1991GSLSP..58....1T. doi:10.1144/GSL.SP.1991.058.01.01. S2CID 140633845.
+"Treaty Series – Convention on the Continental Shelf, 1958" (PDF). United Nations. 29 April 1958. Retrieved 13 January 2016.
+Wellner, J.S.; Heroy, D.C.; Anderson, J.B. (April 2006). "The death mask of the antarctic ice sheet: Comparison of glacial geomorphic features across the continental shelf". Geomorphology. 75 (1–2): 157–171. Bibcode:2006Geomo..75..157W. doi:10.1016/j.geomorph.2005.05.015.
+
+== External links ==
+Office of Naval Research: Ocean Regions: Continental Margin & Rise
+UNEP Shelf Programme
+GEBCO world map 2014
+Anna Cavnar, Accountability and the Commission on the Limits of the Continental Shelf: Deciding Who Owns the Ocean Floor

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+---
+title: "Continental shelf pump"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Continental_shelf_pump"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:39.905353+00:00"
+instance: "kb-cron"
+---
+
+In oceanic biogeochemistry, the continental shelf pump is proposed to operate in the shallow waters of the continental shelves, acting as a mechanism to transport carbon (as either dissolved or particulate material) from surface waters to the interior of the adjacent deep ocean.
+
+
+== Overview ==
+Originally formulated by Tsunogai et al. (1999), the pump is believed to occur where the solubility and biological pumps interact with a local hydrography that feeds dense water from the shelf floor into sub-surface (at least subthermocline) waters in the neighbouring deep ocean.  Tsunogai et al.'s (1999) original work focused on the East China Sea, and the observation that, averaged over the year, its surface waters represented a sink for carbon dioxide.  This observation was combined with others of the distribution of dissolved carbonate and alkalinity and explained as follows :
+
+the shallowness of the continental shelf restricts convection of cooling water
+as a consequence, cooling is greater for continental shelf waters than for neighbouring open ocean waters
+this leads to the production of relatively cool and dense water on the shelf
+the cooler waters promote the solubility pump and lead to an increased storage of dissolved inorganic carbon
+this extra carbon storage is augmented by the increased biological production characteristic of shelves
+the dense, carbon-rich shelf waters sink to the shelf floor and enter the sub-surface layer of the open ocean via isopycnal mixing
+
+
+== Modern Continental Shelf Pump Theory ==
+Continental shelves make up approximately 7% of the oceans area yet have significant roles in oceanic biogeochemical processes. Continental shelves have a large input of terrestrial nutrients and shallow waters that provide productive conditions for biological organisms, and they can be variable due to inputs of dissolved inorganic carbon (DIC) from estuaries, which can influence both the salinity and alkalinity. During the summer and spring, CO2 that is taken up by phytoplankton on the continental shelf sinks below the seasonal thermocline. The thermocline limits atmospheric exchange of carbon, resulting in a CO2 sink. The CO2 below the thermocline is then converted from particulate organic carbon (POC) to dissolved inorganic carbon (DIC) by heterotrophs. This was shown in a study of the East China Sea by Tsunogai et al. (1999) that the thermocline in these regions is highly stratified by density, which allows for the export of dissolved inorganic carbon (DIC) and particulate organic carbon (POC) to deeper regions of the ocean. In addition, the drawn down of CO2 along the continental shelves has been further demonstrated in the North Sea and Celtic Sea. The DIC is transported into the deep ocean by currents that occur along continental shelves.
+
+
+== Modeling ==
+Most of the current models of the global circulation in the ocean do not account for the processes that occur on continental shelves. The coastal processes were largely thought to have an insignificant impact on the ocean's carbon cycling processes compared to the vast open ocean. In the study by Yool and Fasham (2001), they modified the general circulation model (GCM) of the ocean using parametric equations to include them impacts of the continental shelf pump, and they estimated that the export of the world's continental shelves is approximately 0.589 Gt C yr−1.
+In 2009, researchers applied a large-scale hydrodynamic model simulation to assess carbon transport from shelf seas to the deep ocean and carbon sink sufficiency at the European Continental shelf. Combining an Atlantic Margin Model simulation and Proudman Oceanographic Laboratory Coastal-Ocean Modeling System allowed them to reproduce conditions from 1960-2004, with the main focus on hydrodynamics and calculating the correlating biogeochemical effects. They found that 40% of carbon sequestered was heterogeneously removed in a single growing season, with variable removal in some areas, and that only 52% of this carbon was redirected to the deep ocean. In this case, shelf and deep sea circulation must be coupled.
+
+
+== Significance ==
+Based on their measurements of the CO2 flux over the East China Sea (35 g C m−2 y−1), Tsunogai et al. (1999) estimated that the continental shelf pump could be responsible for an air-to-sea flux of approximately 1 Gt C y−1 over the world's shelf areas.  Given that observational and modelling of anthropogenic emissions of CO2 estimates suggest that the ocean is currently responsible for the uptake of approximately 2 Gt C y−1, and that these estimates are poor for the shelf regions, the continental shelf pump may play an important role in the ocean's carbon cycle.
+One caveat to this calculation is that the original work was concerned with the hydrography of the East China Sea, where cooling plays the dominant role in the formation of dense shelf water, and that this mechanism may not apply in other regions.  However, it has been suggested that other processes may drive the pump under different climatic conditions.  For instance, in polar regions, the formation of sea-ice results in the extrusion of salt that may increase seawater density.  Similarly, in tropical regions, evaporation may increase local salinity and seawater density.
+The strong sink of CO2 at temperate latitudes reported by Tsunogai et al. (1999) was later confirmed in the Gulf of Biscay, the Middle Atlantic Bight and the North Sea.  On the other hand, in the sub-tropical South Atlantic Bight reported a source of CO2 to the atmosphere.
+Recently, work has compiled and scaled available data on CO2 fluxes in coastal environments, and shown that globally marginal seas act as a significant CO2 sink (-1.6 mol C m−2 y−1; -0.45 Gt C y−1) in agreement with previous estimates. However, the global sink of CO2 in marginal seas could be almost fully compensated by the emission of CO2 (+11.1 mol C m−2 y−1; +0.40 Gt C y−1) from the ensemble of near-shore coastal ecosystems, mostly related to the emission of CO2 from estuaries (0.34 Gt C y−1).
+An interesting application of this work has been examining the impact of sea level rise over the last de-glacial transition on the global carbon cycle. During the last glacial maximum sea level was some 120 m (390 ft) lower than today. As sea level rose the surface area of the shelf seas grew and in consequence the strength of the shelf sea pump should increase.
+The effect of warming is of particular concern around the Antarctic ice shelves, as the ice sheets are the largest of the Earth’s ice reservoirs and changes in their mass has the greatest potential to have a significant impact on rising sea levels. An eddying global climate model revealed that the shelf is governed by different mechanisms: the Circumpolar Deep Water (CDW) initiates with deep shelf warming with vertical mixing and the Antarctic Slope Front (ASF) utilizes a lateral density gradient near the shelf break. The disconnect between the CDW and ASF can complicate heat transfer across the ASF and prevent heat from escaping deeper waters. But in areas where this transport is less inhibited, heat is able to move to shore and disperse. Gaining a more rounded understanding of this shelf pump could help researchers to better anticipate the effect of warming on ice sheets.
+
+
+== References ==
+
+
+== See also ==
+Biological pump
+Ocean acidification
+Solubility pump

data/en.wikipedia.org/wiki/Coral_reef-0.md

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+---
+title: "Coral reef"
+chunk: 1/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
+Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny, and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian.
+Sometimes called rainforests of the sea, shallow coral reefs form some of Earth's most diverse ecosystems. They occupy less than 0.1% of the world's ocean area, about half the area of France. Yet, they provide a home for at least 25% of all marine species, including fish, mollusks, worms, crustaceans, echinoderms, sponges, tunicates and other cnidarians. Coral reefs flourish in ocean waters that provide few nutrients. They are most commonly found at shallow depths in tropical waters, but deep water and cold water coral reefs exist on smaller scales in other areas.
+Shallow tropical coral reefs have declined by 50% since 1950, partly because they are sensitive to water conditions. They are under threat from excess nutrients (nitrogen and phosphorus), rising ocean heat content and acidification, overfishing (e.g., from blast fishing, cyanide fishing, spearfishing on scuba), sunscreen use, and harmful land-use practices, including runoff and seeps (e.g., from injection wells and cesspools).
+Coral reefs deliver ecosystem services for tourism, fisheries, and shoreline protection. The annual global economic value of coral reefs has been estimated at anywhere from US$30–375 billion (1997 and 2003 estimates) to US$2.7 trillion (a 2020 estimate) to US$9.9 trillion (a 2014 estimate).
+
+== Formation ==
+
+Most coral reefs were formed after the Last Glacial Period when melting ice caused sea level to rise and flood continental shelves. Most coral reefs are less than 10,000 years old. As communities established themselves, the reefs grew upward, keeping pace with rising sea levels. Reefs that rose too slowly could become drowned, without sufficient light. Coral reefs are also found in the deep sea away from continental shelves, around oceanic islands and atolls. The majority of these islands are volcanic in origin. Others have tectonic origins where plate movements lifted the deep ocean floor.
+In The Structure and Distribution of Coral Reefs, Charles Darwin set out his theory of the formation of atoll reefs, an idea he conceived during the voyage of the Beagle. He theorized that uplift and subsidence of Earth's oceanic crust beneath the oceans formed the atolls. Darwin set out a sequence of three stages in atoll formation. A fringing reef forms around an extinct volcanic island as the island and ocean floor subside. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef.
+
+Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the underlying earth allows, corals grow along the coast to form fringing reefs, which can eventually become barrier reefs.
+
+Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies. If the land subsides slowly, the fringing reefs keep pace by growing upward on a base of older, dead coral, forming a barrier reef that encloses a lagoon between the reef and the land. A barrier reef can encircle an island, and once the island sinks below sea level, a roughly circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs and atolls do not usually form complete circles but are broken in places by storms. Like sea level rise, a rapidly subsiding bottom can overwhelm coral growth, killing the coral and the reef, due to what is called coral drowning. Corals that rely on zooxanthellae can die when the water becomes too deep for their symbionts to adequately photosynthesize, due to decreased light exposure.
+The two main variables determining the geomorphology, or shape, of coral reefs are the nature of the substrate on which they rest, and the history of the change in sea level relative to that substrate.
+The approximately 20,000-year-old Great Barrier Reef offers an example of how coral reefs formed on continental shelves. Sea level was then 120 m (390 ft) lower than in the 21st century. As sea level rose, the water and the corals encroached on what had been hills of the Australian coastal plain. By 13,000 years ago, sea level had risen to 60 m (200 ft) lower than at present, and many hills of the coastal plains had become continental islands. As sea level rise continued, water topped most of the continental islands. The corals could then overgrow the hills, forming cays and reefs. Sea level on the Great Barrier Reef has not changed significantly in the last 6,000 years. The age of living reef structure is estimated to be between 6,000 and 8,000 years. Although the Great Barrier Reef formed along a continental shelf, and not around a volcanic island, Darwin's principles apply. Development stopped at the barrier reef stage, since Australia is not about to submerge. It formed the world's largest barrier reef, 300–1,000 m (980–3,280 ft) from shore, stretching for 2,000 km (1,200 mi).
+Healthy tropical coral reefs grow horizontally from 1 to 3 cm (0.39 to 1.18 in) per year, and grow vertically anywhere from 1 to 25 cm (0.39 to 9.84 in) per year; however, they grow only at depths shallower than 150 m (490 ft) because of their need for sunlight, and cannot grow above sea level.

data/en.wikipedia.org/wiki/Coral_reef-1.md

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+---
+title: "Coral reef"
+chunk: 2/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+=== Material ===
+As the name implies, coral reefs are made up of coral skeletons from mostly intact coral colonies. As other chemical elements present in corals become incorporated into the calcium carbonate deposits, aragonite is formed. However, shell fragments and the remains of coralline algae such as the green-segmented genus Halimeda can add to the reef's ability to withstand damage from storms and other threats. Such mixtures are visible in structures such as Eniwetok Atoll.
+
+=== In the geologic past ===
+
+The times of maximum reef development were in the Middle Cambrian (513–501 Ma), Devonian (416–359 Ma) and Carboniferous (359–299 Ma), owing to extinct order Rugosa corals, and Late Cretaceous (100–66 Ma) and Neogene (23 Ma–present), owing to order Scleractinia corals.
+Not all reefs in the past were formed by corals: those in the Early Cambrian (542–513 Ma) resulted from calcareous algae and archaeocyathids (small animals with conical shape, probably related to sponges) and in the Late Cretaceous (100–66 Ma), when reefs formed by a group of bivalves called rudists existed; one of the valves formed the main conical structure and the other, much smaller valve acted as a cap.
+Measurements of the oxygen isotopic composition of the aragonitic skeleton of coral reefs, such as Porites, can indicate changes in sea surface temperature and sea surface salinity conditions during the growth of the coral. Climate scientists often use this technique to infer a region's paleoclimate.
+
+== Types ==
+Since Darwin's identification of the three classical reef formations – the fringing reef around a volcanic island becoming a barrier reef and then an atoll – scientists have identified further reef types. While some sources find only three, Thomas lists "Four major forms of large-scale coral reefs" – the fringing reef, barrier reef, atoll and table reef based on Stoddart, D.R. (1969).  Spalding et al. list four main reef types that can be clearly illustrated  – the fringing reef, barrier reef, atoll, and "bank or platform reef"—and notes that many other structures exist which do not conform easily to strict definitions, including the "patch reef".
+
+=== Fringing reef ===
+
+A fringing reef, also called a shore reef, is directly attached to a shore, or borders it with an intervening narrow, shallow channel or lagoon. It is the most common reef type.  Fringing reefs follow coastlines and can extend for many kilometres. They are usually less than 100 metres wide, but some are hundreds of metres wide. Fringing reefs are initially formed on the shore at the low water level and expand seawards as they grow in size. The final width depends on where the seabed begins to drop steeply. The surface of the fringe reef generally remains at the same height: just below the waterline. In older fringing reefs, with outer regions pushed far out into the sea, the inner part is deepened by erosion and eventually forms a lagoon. Fringing reef lagoons can become over 100 metres wide and several metres deep. Like the fringing reef itself, they run parallel to the coast. The fringing reefs of the Red Sea are "some of the best developed in the world" and occur along all its shores except off sandy bays.
+
+=== Barrier reef ===
+
+Barrier reefs are separated from a mainland or island shore by a deep channel or lagoon. They resemble the later stages of a fringing reef with its lagoon, but differ from the latter mainly in size and origin. Their lagoons can be several kilometres wide and 30 to 70 metres deep. Above all, the offshore outer reef edge formed in open water rather than next to a shoreline. Like an atoll, it is thought that these reefs are formed either as the seabed lowered or the sea level rose. Formation takes considerably longer than for a fringing reef; thus, barrier reefs are much rarer.
+The best known and largest example of a barrier reef is the Australian Great Barrier Reef. Other major examples are the Mesoamerican Barrier Reef System and the New Caledonian Barrier Reef. Barrier reefs are also found on the coasts of Providencia, Mayotte, the Gambier Islands, on the southeast coast of Kalimantan, on parts of the coast of Sulawesi, southeastern New Guinea and the south coast of the Louisiade Archipelago.
+
+=== Platform reef ===
+
+Platform reefs, variously called bank or table reefs, can form on the continental shelf, as well as in the open ocean, in fact anywhere where the seabed rises close enough to the surface of the ocean to enable the growth of zooxanthemic, reef-forming corals. Platform reefs are found in the southern Great Barrier Reef, the Swain and Capricorn Group on the continental shelf, about 100–200 km from the coast. Some platform reefs of the northern Mascarenes are several thousand kilometres from the mainland. Unlike fringing and barrier reefs, which extend only seaward, platform reefs grow in all directions. They are variable in size, ranging from a few hundred metres to many kilometres across. Their usual shape is oval to elongated. Parts of these reefs can reach the surface, forming sandbanks and small islands around which fringing reefs may form. A lagoon may form in the middle of a platform reef.
+Platform reefs are typically situated within atolls, where they adopt the name "patch reefs" and often span a diameter of just a few dozen meters. When platform reefs develop along elongated structures, such as old, weathered barrier reefs, they tend to form a linear arrangement. This is the case, for example, on the east coast of the Red Sea near Jeddah. In old platform reefs, the inner part can be so heavily eroded that it forms a pseudo-atoll. These can be distinguished from real atolls only by detailed investigation, possibly including core drilling. Some platform reefs of the Laccadives are U-shaped, due to wind and water flow.
+
+=== Atoll ===

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+---
+title: "Coral reef"
+chunk: 11/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+Coral gardens take advantage of a coral's natural ability to fragment and continue to grow if the fragments can anchor themselves onto new substrates. This method was first tested by Baruch Rinkevich in 1995 which found success at the time. By today's standards, coral farming has evolved into various forms, but it still aims to cultivate corals. Consequently, coral farming quickly replaced previously used transplantation methods, which involved physically moving sections or entire coral colonies to a new area. Transplantation has seen success in the past, and decades of experiments have led to a high success and survival rate. However, this method still requires removing corals from existing reefs. Given the current state of reefs, this method should generally be avoided if possible. Saving healthy corals from eroding substrates or reefs doomed to collapse could be a significant advantage of using transplantation.
+Coral gardens generally take on safe forms, no matter where you go. It begins with the establishment of a nursery where operators can observe and care for coral fragments. It goes without saying that nurseries should be established in areas that are going to maximize growth and minimize mortality. Floating offshore coral trees or even aquariums are possible locations where corals can grow. After a location has been determined, collection and cultivation can occur.
+The primary benefit of using coral farms is that they reduce polyp and juvenile mortality. By removing predators and recruitment obstacles, corals can mature without much hindrance. However, nurseries cannot stop climate stressors. Warming temperatures or hurricanes can still disrupt or even kill nursery corals.
+Technology is becoming more popular in the coral farming process. Teams from the Reef Restoration and Adaptation Program (RRAP) have trialled coral-counting technology using a prototype robotic camera. The camera uses computer vision and machine learning algorithms to detect and count individual coral babies, and to track their growth and health in real time. This technology, led by QUT, is intended for use during annual coral spawning events and will provide researchers with control not currently possible when mass-producing corals.
+
+=== Creating substrates ===
+
+Efforts to expand the size and number of coral reefs generally involve supplying substrate to allow more corals to find a home. Substrate materials include discarded vehicle tires, scuttled ships, subway cars, and formed concrete, such as reef balls. Reefs grow unaided on marine structures such as oil rigs. In large restoration projects, propagated hermatypic coral on substrate can be secured with metal pins, superglue, or milliput. Needle and thread can also attach A-hermatype coral to the substrate.
+Biorock is a substrate produced by a patented process that runs low-voltage electrical currents through seawater to cause dissolved minerals to precipitate onto steel structures. The resultant white carbonate (aragonite) is the same mineral that makes up natural coral reefs. Corals rapidly colonize and grow on these coated structures. The electrical currents also accelerate the formation and growth of both chemical limestone rock and the skeletons of corals and other shell-bearing organisms, such as oysters. The vicinity of the anode and cathode provides a high pH environment, which inhibits the growth of competing filamentous and fleshy algae. The increased growth rates depend entirely on accretion activity. Under the influence of an electric field, corals exhibit increased growth rates, sizes, and densities.
+Simply having many structures on the ocean floor is not enough to form coral reefs. Restoration projects must consider the complexity of the substrates they are creating for future reefs. Researchers conducted an experiment near Ticao Island in the Philippines in 2013 where several substrates in varying complexities were laid in the nearby degraded reefs. Large complexity consisted of plots with both human-made substrates (smooth and rough rocks) and a surrounding fence; medium consisted of only the human-made substrates; and small had neither the fence nor substrates. After one month, researchers found a positive correlation between structural complexity and larval recruitment rates. The medium complexity performed the best, with larvae favoring rough rocks over smooth rocks. After one year of their study, researchers visited the sites and found that many supported local fisheries. They concluded that reef restoration could be done cost-effectively and would yield long-term benefits if protected and maintained.
+
+=== Relocation ===
+
+One case study with coral reef restoration was conducted on the island of Oahu in Hawaii. The University of Hawaii operates a Coral Reef Assessment and Monitoring Program to help relocate and restore coral reefs in Hawaii. A boat channel from the island of Oahu to the Hawaii Institute of Marine Biology on Coconut Island was overcrowded with coral reefs. Many coral reef patches in the channel had been damaged by past dredging.
+Dredging covers corals with sand. Coral larvae cannot settle on sand; they can only build on existing reefs or compatible hard surfaces, such as rock or concrete. Because of this, the university decided to relocate some of the coral. They transplanted them with the help of United States Army divers to a site relatively close to the channel. They observed little to no damage to any of the colonies during transport, and no coral reef mortality at the transplant site. While attaching the coral to the transplant site, they found that coral placed on hard rock grew well, including on the wires connecting it to the site.
+No environmental effects were seen from the transplantation process, recreational activities were not decreased, and no scenic areas were affected.
+As an alternative to transplanting coral themselves, juvenile fish can also be encouraged to relocate to existing coral reefs by auditory simulation. In damaged sections of the Great Barrier Reef, loudspeakers playing recordings of healthy reef environments were found to attract fish twice as often as equivalent patches where no sound was played, and also increased species biodiversity by 50%.

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+---
+title: "Coral reef"
+chunk: 12/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+=== Heat-tolerant symbionts ===
+Another possibility for coral restoration is gene therapy: inoculating coral with genetically modified bacteria, or naturally occurring heat-tolerant varieties of coral symbiotes, may make it possible to grow corals that are more resistant to climate change and other threats. Warming oceans are forcing corals to adapt to unprecedented temperatures. Those that do not have a tolerance for the elevated temperatures experience coral bleaching and eventually mortality. There is already research aimed at creating genetically modified corals that can withstand a warming ocean. Madeleine J. H. van Oppen, James K. Oliver, Hollie M. Putnam, and Ruth D. Gates described four levels of human intervention for genetically modifying corals, each increasing in intensity. These methods focus on altering the genetics of the zooxanthellae within coral rather than the alternative.
+The first method is to induce acclimatization of the first generation of corals. The idea is that when adult and offspring corals are exposed to stressors, the zooxanthellae will gain a mutation. This method is based primarily on the chance that the zooxanthellae will acquire the specific trait that will enable them to better survive in warmer waters. The second method focuses on identifying the different kinds of zooxanthellae within the coral and on determining how many of each live within the coral at a given age. Use of zooxanthellae from the previous method would only boost success rates for this method. However, this method would only apply to younger corals for now, because previous experiments manipulating zooxanthellae communities at later life stages have all failed. The third method focuses on selective breeding tactics. Once selected, corals would be reared and exposed to simulated stressors in a laboratory.  The last method is to genetically modify the zooxanthellae themselves. When preferred mutations are acquired, the genetically modified zooxanthellae will be introduced to an aposymbiotic polyp, and a new coral will be produced. This method is the most labor-intensive of the fourth, but researchers believe it should be used more and holds the most significant promise for genetic engineering in coral restoration.
+
+=== Invasive algae ===
+Hawaiian coral reefs smothered by the spread of invasive algae were managed with a two-pronged approach: divers manually removed invasive algae, with support from super-sucker barges. Grazing pressure on invasive algae needed to be increased to prevent regrowth. Researchers found that native collector urchins were a reasonable candidate for algae biocontrol to extirpate the remaining invasive algae from the reef.
+
+==== Invasive algae in Caribbean reefs ====
+
+Macroalgae, or seaweed, have the potential to cause reef collapse because they can outcompete many coral species. Macroalgae can overgrow corals, shade them, block recruitment, release biochemicals that can hinder spawning, and potentially form bacteria harmful to corals. Historically, algae growth was controlled by herbivorous fish and sea urchins. Parrotfish are a prime example of reef caretakers. Consequently, these two species can be considered keystone species in reef environments due to their role in protecting reefs.
+Before the 1980s, Jamaica's reefs were thriving and well cared for; however, this all changed after Hurricane Allen occurred in 1980 and an unknown disease spread across the Caribbean. In the wake of these events, massive damage was caused to both the reefs and the sea urchin population across Jamaican reefs and into the Caribbean Sea. As little as 2% of the original sea urchin population survived the disease. Primary macroalgae succeeded the destroyed reefs, and eventually larger, more resilient macroalgae soon took their place as the dominant organism. Parrotfish and other herbivorous fish were few in numbers because of decades of overfishing and bycatch at the time. Historically, the Jamaican coast had 90% coral cover and was reduced to 5% in the 1990s. Eventually, corals were able to recover in areas where sea urchin populations were increasing. Sea urchins fed, multiplied, and cleared substrates, leaving areas for coral polyps to anchor and mature. However, sea urchin populations are still not recovering as fast as researchers predicted, despite being highly fecund. It is unknown whether or not the mysterious disease is still present and preventing sea urchin populations from rebounding. Regardless, these areas are slowly recovering with the aid of sea urchin grazing. This event supports an early restoration idea of cultivating and releasing sea urchins into reefs to prevent algal overgrowth.
+
+=== Microfragmentation and fusion ===
+In 2014, Christopher Page, Erinn Muller, and David Vaughan from the International Center for Coral Reef Research & Restoration at Mote Marine Laboratory in Summerland Key, Florida developed a new technology called "microfragmentation", in which they use a specialized diamond band saw to cut corals into 1 cm2 fragments instead of 6 cm2 to advance the growth of brain, boulder, and star corals. Corals Orbicella faveolata and Montastraea cavernosa were outplanted off the Florida's shores in several microfragment arrays. After two years, O. faveolata had grown 6.5x its original size while M. cavernosa had grown nearly twice its size. Under conventional means, both corals would have required decades to reach the same size. It is suspected that if predation events had not occurred near the beginning of the experiment O. faveolata would have grown at least ten times its original size. By using this method, Mote Marine Laboratory successfully generated 25,000 corals within a single year, subsequently transplanting 10,000 of them into the Florida Keys. Shortly after, they discovered that these microfragments fused with other microfragments from the same parent coral. Typically, corals that are not from the same parent fight and kill nearby corals in an attempt to survive and expand. This new technology, known as "fusion," has been shown to grow coral heads in just 2 years, rather than the typical 25–75 years. After fusion occurs, the reef will act as a single organism rather than several independent reefs.  Currently, no published research has been conducted on this method.
+
+== See also ==

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+title: "Coral reef"
+chunk: 13/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+Deep-water coral — Corals living in the cold waters of deeper, darker parts of the oceans
+Mesophotic coral reef — Corals living in the mesopelagic or twilight zone
+Fossil Coral Reef – National Natural Landmark in Le Roy, New York
+Census of Coral Reefs – Field project of the Census of Marine Life
+Catlin Seaview Survey
+Coral reef organizations
+Sponge reef – Reefs produced by sea sponges
+Pseudo-atoll – Island that encircles a lagoon
+
+== References ==
+
+== Further references ==
+Coral Reef Protection: What Are Coral Reefs?. US EPA.
+UNEP. 2004. Coral Reefs in the South China Sea. UNEP/GEF/SCS Technical Publication No. 2.
+UNEP. 2007. Coral Reefs Demonstration Sites in the South China Sea. UNEP/GEF/SCS Technical Publication No. 5.
+UNEP, 2007. National Reports on Coral Reefs in the Coastal Waters of the South China Sea. UNEP/GEF/SCS Technical Publication No. 11.
+
+== External links ==
+
+"Coral Reef Factsheet". Waitt Institute. Archived from the original on 9 June 2015. Retrieved 8 June 2015.
+Corals and Coral Reefs overview at the Smithsonian Ocean Portal
+About Corals Archived 26 December 2013 at the Wayback Machine Australian Institute of Marine Science.
+International Coral Reef Initiative
+Moorea Coral Reef Long Term Ecological Research Site (US NSF)
+ARC Centre of Excellence for Coral Reef Studies
+NOAA's Coral-List Listserver for Coral Reef Information and News
+NOAA's Coral Reef Conservation Program
+NOAA's Coral Reef Information System
+ReefBase: A Global Information System on Coral Reefs Archived 31 August 2012 at the Wayback Machine
+National Coral Reef Institute Archived October 23, 2012, at the Wayback Machine Nova Southeastern University
+Marine Aquarium Council Archived 24 July 2013 at the Wayback Machine
+NCORE National Center for Coral Reef Research University of Miami
+Science and Management of Coral Reefs in the South China Sea and Gulf of Thailand
+Microdocs Archived 27 July 2011 at the Wayback Machine: 4 kinds of Reef Archived 24 October 2012 at the Wayback Machine & Reef structure Archived 24 October 2012 at the Wayback Machine
+Reef Relief Active Florida environmental non-profit focusing on coral reef education and protection
+Global Reef Record – Catlin Seaview Survey of the reef, a database of images and other information
+"Corals and Coral Reefs" (archived). Nancy Knowlton, iBioSeminars, 2011.
+Nancy Knowlton's Seminar: "Corals and Coral Reefs". Nancy Knowlton, iBioSeminars, 2011.
+About coral reefs Living Reefs Foundation, Bermuda
+"Caribbean Coral Reefs – Status Report 1970-2012" by the IUCN. – Video on YouTube, featuring the report.

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+title: "Coral reef"
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+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+Atolls or atoll reefs are a more or less circular or continuous barrier reef that extends all the way around a lagoon without a central island. They are usually formed from fringing reefs around volcanic islands. Over time, the island erodes away and sinks below sea level.  Atolls may also be formed by the sinking of the seabed or rising of the sea level. A ring of reefs results, which encloses a lagoon.  Atolls are numerous in the South Pacific, where they usually occur in mid-ocean, for example, in the Caroline Islands, the Cook Islands, French Polynesia, the Marshall Islands, and Micronesia.
+Atolls are found in the Indian Ocean, for example, in the Maldives, the Chagos Islands, the Seychelles, and around Cocos Island. The entire Maldives consists of 26 atolls.
+
+=== Other reef types or variants ===
+
+Apron reef – short reef resembling a fringing reef, but more sloped; extending out and downward from a point or peninsular shore. The initial stage of a fringing reef.
+Bank reef – isolated, flat-topped reef larger than a patch reef and usually on mid-shelf regions and linear or semi-circular in shape; a type of platform reef.
+Patch reef – common, isolated, comparatively small reef outcrop, usually within a lagoon or embayment, often circular and surrounded by sand or seagrass. It can be considered as a type of platform reef  or as features of fringing reefs, atolls, and barrier reefs. The patches may be surrounded by a ring of reduced seagrass cover referred to as a grazing halo.
+Ribbon reef – long, narrow, possibly winding reef, usually associated with an atoll lagoon and also called a shelf-edge reef or sill reef.
+Drying reef – a part of a reef which is above water at low tide but submerged at high tide
+Habili – reef specific to the Red Sea; does not reach near enough to the surface to cause visible surf; may be a hazard to ships (from the Arabic for "unborn")
+Microatoll – community of species of corals; vertical growth limited by average tidal height; growth morphologies offer a low-resolution record of patterns of sea level change; fossilized remains can be dated using radioactive carbon dating and have been used to reconstruct Holocene sea levels
+Cays – small, low-elevation, sandy islands formed on the surface of coral reefs from eroded material that piles up, creating an area above sea level; can be stabilized by plants to become habitable; occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans (including the Caribbean and on the Great Barrier Reef and Belize Barrier Reef), where they provide habitable and agricultural land
+Seamount or guyot – formed when a coral reef on a volcanic island subsides; tops of seamounts are rounded, and guyots are flat; flat tops of guyots, or tablemounts, are due to erosion by waves, winds, and atmospheric processes
+
+== Zones ==
+
+Coral reef ecosystems contain distinct zones that host different kinds of habitats. Usually, three major zones are recognized: the fore reef, the reef crest, and the back reef (also called the reef lagoon).
+The three zones are physically and ecologically interconnected. Reef life and oceanic processes create opportunities for the exchange of seawater, sediment, nutrients, and marine life.
+Most coral reefs exist in waters less than 50 m deep. Some inhabit tropical continental shelves where cool, nutrient-rich upwelling does not occur, such as the Great Barrier Reef. Others are found in the deep ocean surrounding islands or as atolls, such as in the Maldives. The reefs surrounding islands form when islands subside into the ocean, and atolls form when an island subsides below the surface of the sea.
+Alternatively, Moyle and Cech distinguish six zones, though most reefs possess only some of the zones.

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+title: "Coral reef"
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+category: "reference"
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+
+The reef surface is the shallowest part of the reef. It is subject to surge and tides. When waves pass over shallow areas, they shoal, as shown in the adjacent diagram. This means the water is often agitated. These are the precise conditions under which corals flourish. The light is sufficient for photosynthesis by the symbiotic zooxanthellae, and agitated water brings plankton to feed the coral.
+The off-reef floor is the shallow sea floor surrounding a reef. This zone occurs next to reefs on continental shelves. Reefs around tropical islands and atolls drop abruptly to great depths and do not have such a floor. Usually sandy, the floor often supports seagrass meadows, which are important foraging areas for reef fish.
+The reef drop-off is, for its first 50 m, habitat for reef fish who find shelter on the cliff face and plankton in the water nearby. The drop-off zone primarily occurs around oceanic islands and atolls.
+The reef face is the zone above the reef floor or the reef drop-off. This zone is often the reef's most diverse area. Coral and calcareous algae provide complex habitats and areas that offer protection, such as cracks and crevices. Invertebrates and epiphytic algae provide much of the food for other organisms. A common feature of this forereef zone is spur and groove formations that serve to transport sediment downslope.
+The reef flat is the sandy-bottomed flat, which can be behind the main reef, containing chunks of coral. This zone may border a lagoon and serve as a protective area, or it may lie between the reef and the shore, and in this case, it is a flat, rocky area. Fish tend to prefer it when it is present.
+The reef lagoon is an entirely enclosed region, which creates an area less affected by wave action and often contains small reef patches.
+However, the topography of coral reefs is constantly changing. Each reef is made up of irregular patches of algae, sessile invertebrates, and bare rock and sand. The size, shape, and relative abundance of these patches change from year to year in response to the various factors that favor one type of patch over another. Growing coral, for example, produces constant change in the fine structure of reefs. On a larger scale, tropical storms may knock out large sections of reef and cause boulders in sandy areas to move.
+
+== Locations ==
+
+Coral reefs are estimated to cover 284,300 km2 (109,800 sq mi), just under 0.1% of the oceans' surface area. The Indo-Pacific region (including the Red Sea, Indian Ocean, Southeast Asia and the Pacific) account for 91.9% of this total. Southeast Asia accounts for 32.3% of that figure, while the Pacific, including Australia, accounts for 40.8%. Atlantic and Caribbean coral reefs account for 7.6%.
+Although corals exist both in temperate and tropical waters, shallow-water reefs form only in a zone extending from approximately 30° N to 30° S of the equator. Tropical corals do not grow at depths of over 50 meters (160 ft). The optimum temperature for most coral reefs is 26–27 °C (79–81 °F), and few reefs exist in waters below 18 °C (64 °F). When the net production by reef-building corals no longer keeps pace with relative sea level, and the reef structure permanently drowns, a Darwin Point is reached. One such point exists at the northwestern end of the Hawaiian Archipelago; see Evolution of Hawaiian volcanoes#Coral atoll stage.
+However, reefs in the Persian Gulf have adapted to temperatures of 13 °C (55 °F) in winter and 38 °C (100 °F) in summer. 37 species of scleractinian corals inhabit such an environment around Larak Island.
+Deep-water coral inhabits greater depths and colder temperatures at much higher latitudes, as far north as Norway. Although deep water corals can form reefs, little is known about them.
+The northernmost coral reef on Earth is located near Eilat, Israel. Coral reefs are rare along the west coasts of the Americas and Africa, due primarily to upwelling and strong cold coastal currents that reduce water temperatures in these areas (the Humboldt, Benguela, and Canary Currents, respectively). Corals are seldom found along the coastline of South Asia—from the eastern tip of India (Chennai) to the Bangladesh and Myanmar borders—as well as along the coasts of northeastern South America and Bangladesh, due to the freshwater release from the Amazon and Ganges Rivers respectively.
+Significant coral reefs include:

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+title: "Coral reef"
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+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
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+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+The Great Barrier Reef—largest, comprising over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometers (1,600 mi) off Queensland, Australia
+The Mesoamerican Barrier Reef System—second largest, stretching 1,000 kilometers (620 mi) from Isla Contoy at the tip of the Yucatán Peninsula down to the Bay Islands of Honduras
+The New Caledonia Barrier Reef—second longest double barrier reef, covering 1,500 kilometers (930 mi)
+The Andros, Bahamas Barrier Reef—third largest, following the east coast of Andros Island, Bahamas, between Andros and Nassau
+The Red Sea—includes 6,000-year-old fringing reefs located along a 2,000 km (1,240 mi) coastline
+The Florida Reef Tract—largest continental US reef and the third-largest coral barrier reef, extends from Soldier Key, located in Biscayne Bay, to the Dry Tortugas in the Gulf of Mexico
+Blake Plateau has the world's largest known deep-water coral reef, comprising a 6.4 million-acre reef that stretches from Miami to Charleston, S. C. Its discovery was announced in January 2024.
+Pulley Ridge—deepest photosynthetic coral reef, Florida
+Numerous reefs around the Maldives
+The Philippines coral reef area, the second-largest in Southeast Asia, is estimated at 26,000 square kilometres. They are populated by over 900 reef fish species and 400 scleractinian coral species, 12 of which are endemic.
+The Raja Ampat Islands in Indonesia's Southwest Papua province offer the highest known marine diversity.
+Bermuda is known for its northernmost coral reef system, located at 32.4°N 64.8°W / 32.4; -64.8. The presence of coral reefs at this high latitude is due to the proximity of the Gulf Stream. Bermuda coral species represent a subset of those found in the greater Caribbean.
+The world's northernmost individual coral reef is located in the Finlayson Channel, in the inside passage of British Columbia, Canada.
+The world's southernmost coral reef is at Lord Howe Island, in the Pacific Ocean off the east coast of Australia.
+
+== Coral ==
+
+When alive, corals are colonies of small animals embedded in calcium carbonate shells. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes. Polyps are usually tiny, but they can range in size from a pinhead to 12 inches (30 cm) across.
+Reef-building or hermatypic corals live only in the photic zone (above 70 m), the depth to which sufficient sunlight penetrates the water.
+
+=== Zooxanthellae ===
+
+Coral polyps do not photosynthesize, but have a symbiotic relationship with microscopic algae (dinoflagellates) of the genus Symbiodinium, commonly referred to as zooxanthellae. These organisms live within the polyps' tissues and provide organic nutrients that nourish the polyp in the form of glucose, glycerol, and amino acids. Because of this relationship, coral reefs grow much faster in clear water, which admits more sunlight. Without their symbionts, coral growth would be too slow to form significant reef structures. Corals get up to 90% of their nutrients from their symbionts. In return, as an example of mutualism, the corals shelter the zooxanthellae, averaging one million for every cubic centimetre of coral, and provide a constant supply of the carbon dioxide they need for photosynthesis.
+
+The varying pigments in different species of zooxanthellae give them an overall brown or golden-brown appearance and give brown corals their colors. Other pigments, such as reds, blues, and greens, are produced by colored proteins in coral animals. Coral that loses a significant fraction of its zooxanthellae becomes white (or sometimes pastel shades in corals that are pigmented with their own proteins) and is said to be bleached, a condition which, unless corrected, can kill the coral.
+There are eight clades of Symbiodinium phylotypes. Most research has been conducted on clades A–D. Each clade contributes both benefits and less compatible attributes to the survival of its coral hosts. Each photosynthetic organism has a specific level of sensitivity to photodamage to compounds needed for survival, such as proteins. Rates of regeneration and replication determine the organism's ability to survive. Phylotype A is found more in the shallow waters. It can produce mycosporine-like amino acids that are UV-resistant, using a derivative of glycerin to absorb UV radiation, thereby allowing them to better adapt to warmer water temperatures. In the event of UV or thermal damage, if and when repair occurs, it will increase the likelihood of survival of the host and symbiont. This leads to the idea that, evolutionarily, clade A is more UV resistant and thermally resistant than the other clades.
+Clades B and C are found more frequently in deeper water, which may explain their higher vulnerability to increased temperatures. Terrestrial plants that receive less sunlight because they are found in the undergrowth are analogous to clades B, C, and D. Since clades B through D are found at deeper depths, they require an elevated light absorption rate to be able to synthesize as much energy. With elevated absorption rates at UV wavelengths, these phylotypes are more prone to coral bleaching than the shallow clade A.
+Clade D has been observed to be high temperature-tolerant, and has a higher rate of survival than clades B and C during modern bleaching events.
+
+=== Skeleton ===
+
+Reefs grow as polyps and other organisms deposit calcium carbonate, the basis of coral, as a skeletal structure beneath and around themselves, pushing the coral head's top upwards and outwards. Waves, grazing fish (such as parrotfish), sea urchins, sponges and other forces and organisms act as bioeroders, breaking down coral skeletons into fragments that settle into spaces in the reef structure or form sandy bottoms in associated reef lagoons.
+Typical shapes for coral species are named by their resemblance to terrestrial objects such as wrinkled brains, cabbages, table tops, antlers, wire strands, and pillars. These shapes can depend on the life history of the coral, like light exposure and wave action, and events such as breakages.
+
+=== Reproduction ===

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+---
+title: "Coral reef"
+chunk: 6/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+Corals reproduce both sexually and asexually. An individual polyp uses both reproductive modes within its lifetime. Corals reproduce sexually by either internal or external fertilization. The reproductive cells are found on the mesenteries, membranes that radiate inward from the layer of tissue that lines the stomach cavity. Some mature adult corals are hermaphroditic; others are exclusively male or female. A few species change sex as they grow.
+Internally fertilized eggs develop in the polyp for a period ranging from days to weeks. Subsequent development produces a tiny larva, known as a planula. Externally fertilized eggs develop during synchronized spawning. Polyps across a reef simultaneously release eggs and sperm into the water en masse. Spawn disperse over a large area. The timing of spawning depends on the time of year, water temperature, and tidal and lunar cycles. Spawning is most successful when there is little variation between high and low tide. The less water movement, the better the chance for fertilization. The release of eggs or planula usually occurs at night and is sometimes in phase with the lunar cycle (three to six days after a full moon).
+
+The period from release to settlement lasts only a few days, but some planulae can survive afloat for several weeks. During this process, the larvae may use several cues to find a suitable settlement site. At long distances sounds from existing reefs are likely important, while at short distances chemical compounds become important. The larvae are vulnerable to predation and environmental conditions. The lucky few planulae that successfully attach to the substrate then compete for food and space.
+
+== Gallery of reef-building corals ==
+
+== Other reef builders ==
+Corals are the most prodigious reef-builders. However, many other organisms living in the reef community contribute skeletal calcium carbonate in the same manner as corals. These include coralline algae, some sponges and bivalves. Reefs are always built by the combined efforts of these different phyla, with other organisms leading reef-building in other geological periods.
+
+=== Coralline algae ===
+
+Coralline algae are essential contributors to reef structure. Although their mineral deposition rates are much slower than corals, they are more tolerant of rough wave-action, and so help to create a protective crust over those parts of the reef subjected to the most significant forces by waves, such as the reef front facing the open ocean. They also strengthen the reef structure by depositing limestone in sheets over the reef surface. Furthermore, in locations unfavorable to the growth of corals, coralline algae can be the primary builders of an algal reef.
+
+=== Sponges ===
+
+Sponge reefs are reefs produced by sea sponges. Hexactinellid sponges are known to form reefs off the coast of British Columbia, southeast Alaska, and Washington state. Reefs discovered in Hecate Strait, British Columbia, have grown to up to 7 kilometres long and 20 metres high. Hexactinellid sponge reefs were first identified in the Middle Triassic (245–208 million years ago). The sponges reached their full extent in the late Jurassic (201–145 million years ago) when a discontinuous reef system 7,000 km long stretched across the northern Tethys and North Atlantic basins, but have since declined and were thought to be extinct until existing reefs were discovered in 1987–1988.
+Archaeocyatha, an extinct clade of sponges, were the planet's first reef-building animals and are an index fossil for the Lower Cambrian worldwide. Similarly, Stromatoporoidea was another extinct clade of reef-building sponges. Unlike corals, stromatoporoids usually settled on soft substrates, so their 'reefs' occupied only a single level rather than a multi-tiered vertical framework of built-up skeletons.
+
+=== Bivalves ===
+
+Oyster reefs are dense aggregations of oysters living in colonial communities. Other regionally specific names for these structures include oyster beds and oyster banks. Oyster larvae require a hard substrate or surface to attach to, which includes the shells of old or dead oysters. Thus, reefs can build up over time as new larvae settle on older individuals. Crassostrea virginica were once abundant in Chesapeake Bay and shorelines bordering the Atlantic coastal plain until the late nineteenth century. Ostrea angasi is a species of flat oyster that has also formed large reefs in South Australia.
+Hippuritida, an extinct order of bivalves known as rudists, were major reef-building organisms during the Cretaceous. By the mid-Cretaceous, rudists became the dominant tropical reef-builders, becoming more numerous than scleractinian corals. During this period, ocean temperatures and saline levels—which corals are sensitive to—were higher than they are today, which may have contributed to the success of rudist reefs.
+
+=== Gastropods ===
+Some gastropods, like family Vermetidae, are sessile and cement themselves to the substrate, contributing to the reef building.
+
+== Darwin's paradox ==

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+---
+title: "Coral reef"
+chunk: 7/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+In The Structure and Distribution of Coral Reefs, published in 1842, Darwin described how coral reefs were found in some tropical areas but not others, with no obvious cause. The largest and strongest corals grew in parts of the reef exposed to the most violent surf, and corals were weakened or absent where loose sediment accumulated.
+Tropical waters contain few nutrients yet a coral reef can flourish like an "oasis in the desert". This has given rise to the ecosystem conundrum, sometimes called "Darwin's paradox": "How can such high production flourish in such nutrient poor conditions?"
+Coral reefs support over one-quarter of all marine species. This diversity results in complex food webs, with large predator fish eating smaller forage fish, which eat yet smaller zooplankton, and so on. However, all food webs ultimately depend on plants, which serve as primary producers. Coral reefs typically produce 5–10 grams of carbon per square meter per day (gC·m−2·day−1) biomass.
+One reason for the unusual clarity of tropical waters is their nutrient deficiency and drifting plankton. Further, the sun shines year-round in the tropics, warming the surface layer, making it less dense than subsurface layers. The warmer water is separated from deeper, cooler water by a stable thermocline, where the temperature makes a rapid change. This keeps the warm surface waters floating above the cooler, deeper waters. In most parts of the ocean, there is little exchange between these layers. Organisms that die in aquatic environments generally sink to the bottom, where they decompose, which releases nutrients in the form of nitrogen (N), phosphorus (P), and potassium (K). These nutrients are necessary for plant growth, but in the tropics, they do not return directly to the surface.
+Plants form the base of the food chain and need sunlight and nutrients to grow. In the ocean, these plants are mainly microscopic phytoplankton which drift in the water column. They need sunlight for photosynthesis, which powers carbon fixation, so they are found only relatively near the surface, but they also need nutrients. Phytoplankton rapidly use nutrients in the surface waters, and in the tropics, these nutrients are not usually replaced because of the thermocline.
+
+=== Explanations ===
+Around coral reefs, lagoons fill in with material eroded from the reef and the island. They become havens for marine life, protecting them from waves and storms.
+Most importantly, reefs recycle nutrients, which happens much less in the open ocean. In coral reefs and lagoons, producers include phytoplankton, seaweed, and coralline algae, especially small types called turf algae, which transfer nutrients to corals. The phytoplankton form the base of the food chain and are eaten by fish and crustaceans. Recycling reduces the nutrient inputs needed overall to support the community.
+Corals also absorb nutrients, including inorganic nitrogen and phosphorus, directly from water. Many corals extend their tentacles at night to catch zooplankton that pass near. Zooplankton provide the polyp with nitrogen, and the polyp shares some of the nitrogen with the zooxanthellae, which also require this element.
+
+Sponges live in the crevices of reefs. They are efficient filter feeders, and in the Red Sea they consume about 60% of the phytoplankton that drifts by. Sponges eventually excrete nutrients in a form that corals can use.
+The roughness of coral surfaces is key to coral survival in agitated waters. Normally, a boundary layer of still water forms around a submerged object, acting as a barrier. Waves breaking on the extremely rough edges of corals disrupt the boundary layer, allowing the corals access to passing nutrients. Turbulent water thereby promotes reef growth. Without access to nutrients brought by rough coral surfaces, even the most effective recycling would not suffice.
+Deep nutrient-rich water entering coral reefs through isolated events may have significant effects on temperature and nutrient systems. This water movement disrupts the relatively stable thermocline that usually exists between warm shallow water and deeper colder water. Temperature regimes on coral reefs in the Bahamas and Florida are highly variable, spanning temporal scales from minutes to seasons and spatial scales across depths.
+
+Water can pass through coral reefs in various ways, including current rings, surface waves, internal waves, and tidal changes.  Movement is generally created by tides and wind. As tides interact with varying bathymetry and wind mixes with surface water, internal waves are created. An internal wave is a gravity wave that moves along density stratification within the ocean. When a water parcel encounters a different density, it oscillates and creates internal waves. While internal waves generally have a lower frequency than surface waves, they often form as a single wave that breaks into multiple waves as it hits a slope and moves upward. This vertical breakup of internal waves causes significant diapycnal mixing and turbulence. Internal waves can act as nutrient pumps, bringing plankton and cool nutrient-rich water to the surface.
+
+The irregular structure of coral reef bathymetry may enhance mixing, producing pockets of cooler water and variable nutrient levels. Arrival of cool, nutrient-rich water from depths due to internal waves and tidal bores has been linked to growth rates of suspension feeders and benthic algae  as well as plankton and larval organisms. The seaweed Codium isthmocladum reacts to deep water nutrient sources because their tissues have different concentrations of nutrients dependent upon depth. Aggregations of eggs, larval organisms, and plankton on reefs respond to deep water intrusions. Similarly, as internal waves and bores move vertically, surface-dwelling larval organisms are carried toward the shore. This has significant biological importance to cascading effects of food chains in coral reef ecosystems and may provide yet another key to unlocking the paradox.
+Cyanobacteria provide soluble nitrates via nitrogen fixation.
+Coral reefs often depend on surrounding habitats, such as seagrass meadows and mangrove forests, for nutrients. Seagrass and mangroves supply dead plants and animals that are rich in nitrogen and serve to feed fish and animals from the reef by supplying wood and vegetation. Reefs, in turn, protect mangroves and seagrass from waves and produce sediment in which the mangroves and seagrass can root.

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+---
+title: "Coral reef"
+chunk: 8/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+== Biodiversity ==
+
+Coral reefs form some of the world's most productive ecosystems, providing complex and varied marine habitats that support a wide range of organisms. Fringing reefs just below low tide level have a mutually beneficial relationship with mangrove forests at high tide level and sea grass meadows in between: the reefs protect the mangroves and seagrass from strong currents and waves that would damage them or erode the sediments in which they are rooted, while the mangroves and sea grass protect the coral from large influxes of silt, fresh water and pollutants. This level of environmental variety benefits many coral reef animals, which, for example, may feed on seagrass and use the reefs for protection or breeding.
+Reefs are home to a variety of animals, including fish, seabirds, sponges, cnidarians (which includes some types of corals and jellyfish), worms, crustaceans (including shrimp, cleaner shrimp, spiny lobsters and crabs), mollusks (including cephalopods), echinoderms (including starfish, sea urchins and sea cucumbers), sea squirts, sea turtles and sea snakes. Aside from humans, mammals are rare on coral reefs, with visiting cetaceans such as dolphins being the main exception. A few species feed directly on corals, while others graze on algae on the reef. Reef biomass is positively related to species diversity.
+Different species may regularly inhabit the same hideouts in a reef at different times of day. Nighttime predators such as cardinalfish and squirrelfish hide during the day, while damselfish, surgeonfish, triggerfish, wrasses and parrotfish hide from eels and sharks.
+The great number and diversity of hiding places in coral reefs, i.e., refuges, are the most important factors driving the high diversity and high biomass of organisms in coral reefs.
+Coral reefs also have a very high degree of microorganism diversity compared to other environments.
+
+=== Algae ===
+Reefs are chronically at risk of algal encroachment. Overfishing and excess nutrient supply from onshore can enable algae to outcompete and kill the coral. Increased nutrient levels can be a result of sewage or chemical fertilizer runoff. Runoff can carry nitrogen and phosphorus, which promote excess algae growth. Algae can sometimes out-compete the coral for space. The algae can then smother the coral by decreasing the oxygen supply available to the reef. Decreased oxygen levels can slow down calcification rates, weakening the coral and leaving it more susceptible to disease and degradation. Algae inhabit a large percentage of surveyed coral locations. The algal population consists of turf algae, coralline algae and macro algae. Some sea urchins (such as Diadema antillarum) eat these algae and could thus decrease the risk of algal encroachment.
+
+=== Sponges ===
+Sea sponges are an essential component of coral reef communities. There are 420 species of sponges in coral reefs from Indonesia, 486 species in coral reefs from Indian waters, and 1500 species in the Great Barrier Reef from Australia.
+Sponges occupy an important role as detritivores in coral reef food webs by recycling detritus to higher trophic levels through their sponge loop. For example, several sponge species can convert dissolved organic matter (DOM) derived from corals and algae into sponge detritus, which serves as food for species incapable of directly consuming DOM.
+Sponges with photosynthesizing endosymbionts also produce up to three times more oxygen, as well as more organic matter than they consume. Such contributions to their habitats' resources are significant along Australia's Great Barrier Reef but relatively minor in the Caribbean.
+Aside from providing nutrition, sponges also offer microhabitats to various invertebrates and some fish species.
+
+=== Fish ===
+
+Over 4,000 species of fish inhabit coral reefs. The reasons for this diversity remain unclear. Hypotheses include the "lottery", in which the first (lucky winner) recruit to a territory is typically able to defend it against latecomers, "competition", in which adults compete for territory, and less-competitive species must be able to survive in poorer habitat, and "predation", in which population size is a function of postsettlement piscivore mortality. Healthy reefs can produce up to 35 tons of fish per square kilometre each year, but damaged reefs produce much less.
+
+=== Invertebrates ===
+Sea urchins, Dotidae and sea slugs eat seaweed. Some species of sea urchins, such as Diadema antillarum, can play a pivotal part in preventing algae from overrunning reefs. Researchers are investigating the use of native collector urchins, Tripneustes gratilla, for their potential as biocontrol agents to mitigate the spread of invasive algae species on coral reefs. Nudibranchia and sea anemones eat sponges.
+Several invertebrates, collectively called "cryptofauna", inhabit the coral skeletal substrate itself, either boring into the skeletons (through the process of bioerosion) or living in pre-existing voids and crevices. Animals boring into the rock include sponges, bivalve mollusks, and sipunculans. Those settling on the reef include many other species, particularly crustaceans and polychaete worms.
+
+=== Seabirds ===
+Coral reef systems provide important habitats for seabird species, many of which are endangered. For example, Midway Atoll in Hawaii supports nearly three million seabirds, including two-thirds (1.5 million) of the global population of Laysan albatross, and one-third of the global population of black-footed albatross. Each seabird species has specific sites on the atoll where they nest. Altogether, 17 species of seabirds live on Midway. The short-tailed albatross is the rarest, with fewer than 2,200 surviving after excessive feather hunting in the late 19th century.
+
+=== Other ===
+Sea snakes feed exclusively on fish and their eggs. Marine birds, such as herons, gannets, pelicans and boobies, feed on reef fish. Some land-based reptiles intermittently associate with reefs, such as monitor lizards, the marine crocodile and semiaquatic snakes, such as Laticauda colubrina. Sea turtles, particularly hawksbill sea turtles, feed on sponges.

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+---
+title: "Coral reef"
+chunk: 9/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+== Ecosystem services ==
+Coral reefs deliver ecosystem services to tourism, fisheries, and coastline protection. The global economic value of coral reefs has been estimated to be between US$29.8 billion and $375 billion per year. About 500 million people benefit from ecosystem services provided by coral reefs.
+The economic cost of destroying one square kilometre of coral reef over 25 years has been estimated at between $137,000 and $1,200,000.
+To improve the management of coastal coral reefs, the World Resources Institute (WRI) developed and published tools to calculate the value of coral reef-related tourism, shoreline protection, and fisheries, partnering with five Caribbean countries. As of April 2011, published working papers covered St. Lucia, Tobago, Belize, and the Dominican Republic. The WRI was "making sure that the study results support improved coastal policies and management planning". The Belize study estimated the value of reef and mangrove services at $395–559 million annually.
+Bermuda's coral reefs provide economic benefits to the Island worth, on average, $722 million per year, based on six key ecosystem services, according to Sarkis et al. (2010).
+
+=== Shoreline protection ===
+
+Coral reefs protect shorelines by absorbing wave energy, and many small islands would not exist without reefs. Coral reefs can reduce wave energy by 97%, helping to prevent loss of life and property damage. Coastlines protected by coral reefs are also more stable in terms of erosion than those without. Reefs can attenuate waves as well as, or better than, artificial structures designed for coastal defence, such as breakwaters. An estimated 197 million people who live both below 10 m elevation and within 50 km of a reef consequently may receive risk reduction benefits from reefs. Restoring reefs is significantly cheaper than building artificial breakwaters in tropical environments. Expected damages from flooding would double, and costs from frequent storms would triple without the topmost meter of reefs. For 100-year storm events, flood damages would increase by 91% to $US 272 billion without the top meter.
+
+=== Fisheries ===
+About six million tons of fish are taken each year from coral reefs. Well-managed reefs have an average annual yield of 15 tons of seafood per square kilometre. Southeast Asia's coral reef fisheries alone yield about $2.4 billion in seafood annually.
+
+== Threats ==
+
+Since their emergence 485 million years ago, coral reefs have faced many threats, including disease, predation, invasive species, bioerosion by grazing fish, algal blooms, and geologic hazards. Recent human activities present new threats. From 2009 to 2018, coral reefs worldwide declined 14%.
+Human activities that threaten coral include coral mining, bottom trawling, and the digging of canals and accesses into islands and bays, all of which can damage marine ecosystems if not done sustainably. Other localized threats include blast fishing, overfishing, coral overmining, and marine pollution, including use of the banned anti-fouling biocide tributyltin; although absent in developed countries, these activities continue in places with few environmental protections or poor regulatory enforcement. Chemicals in sunscreens may awaken latent viral infections in zooxanthellae and impact reproduction. However, concentrating tourism activities via offshore platforms has been shown to limit the spread of coral disease by tourists.
+Greenhouse gas emissions present a broader threat through sea temperature rise and sea level rise, resulting in widespread coral bleaching and loss of coral cover. Climate change causes more frequent and more severe storms, also changes ocean circulation patterns, which can destroy coral reefs.Ocean acidification also affects corals by decreasing calcification rates and increasing dissolution rates, although corals can adapt their calcifying fluids to changes in seawater pH and carbonate levels to mitigate the impact. Volcanic and human-made aerosol pollution can modulate regional sea surface temperatures.
+In 2011, two researchers suggested that "extant marine invertebrates face the same synergistic effects of multiple stressors" that occurred during the end-Permian extinction. That genus "with poorly buffered respiratory physiology and calcareous shells", such as corals, was particularly vulnerable.
+Corals respond to stress by "bleaching", or expelling their colorful zooxanthellate endosymbionts.  Corals with Clade C zooxanthellae are generally vulnerable to heat-induced bleaching, whereas corals with the hardier Clade A or D are generally resistant, as are tougher coral genera like Porites and Montipora.
+Every 4–7 years, an El Niño event causes some reefs with heat-sensitive corals to bleach, with especially widespread bleachings in 1998 and 2010.  However, reefs that experience a severe bleaching event become resistant to future heat-induced bleaching, due to rapid directional selection.  Similar rapid adaptation may protect coral reefs from global warming.
+A large-scale systematic study of the Jarvis Island coral community, which experienced 10 El Niño-coincident coral bleaching events from 1960 to 2016, found that the reef recovered from near-total mortality after severe events.
+
+== Protection ==

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+---
+title: "Coral reef"
+chunk: 10/13
+source: "https://en.wikipedia.org/wiki/Coral_reef"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:41.179437+00:00"
+instance: "kb-cron"
+---
+
+Marine protected areas (MPAs) are areas designated because they provide various kinds of protection to ocean and/or estuarine areas. They are intended to promote responsible fishery management and habitat protection. MPAs can also encompass social and biological objectives, including reef restoration, aesthetics, biodiversity, and economic benefits.
+The effectiveness of MPAs is still debated. For example, a study investigating the success of a small number of MPAs in Indonesia, the Philippines, and Papua New Guinea found no significant differences between the MPAs and unprotected sites. Furthermore, in some cases they can generate local conflict, due to a lack of community participation, clashing views of the government and fisheries, effectiveness of the area and funding. In some situations, as in the Phoenix Islands Protected Area, MPAs provide revenue to locals. The level of income provided is similar to the income they would have generated without controls. Overall, it appears the MPAs can protect local coral reefs, but that clear management and sufficient funds are required.
+The Caribbean Coral Reefs – Status Report 1970–2012 states that coral decline may be reduced or even reversed. For this, overfishing needs to be stopped, especially fishing on species key to coral reefs, such as parrotfish. Direct human pressure on coral reefs should also be reduced, and the inflow of sewage should be minimised. Measures to achieve this could include restricting coastal settlement, development, and tourism. The report shows that healthier Caribbean reefs are those with large, healthy populations of parrotfish. These occur in countries that protect parrotfish and other species, like sea urchins. They also often ban fish trapping and spearfishing. Together these measures help creating "resilient reefs".
+Protecting networks of diverse and healthy reefs, not only climate refugia, helps ensure the greatest chance of genetic diversity, which is critical for coral to adapt to new climates. A variety of conservation methods applied across marine and terrestrial threatened ecosystems makes coral adaption more likely and effective.
+Designating a reef as a biosphere reserve, marine park, national monument, or world heritage site can offer protection. For example, Belize's barrier reef, Sian Ka'an, the Galapagos islands, Great Barrier Reef, Henderson Island, Palau and Papahānaumokuākea Marine National Monument are world heritage sites.
+In Australia, the Great Barrier Reef is protected by the Great Barrier Reef Marine Park Authority, and is the subject of much legislation, including a biodiversity action plan. Australia compiled a Coral Reef Resilience Action Plan. This plan consists of adaptive management strategies, including reducing carbon footprint. A public awareness plan provides education on the "rainforests of the sea" and how people can reduce carbon emissions.
+Inhabitants of Ahus Island, Manus Province, Papua New Guinea, have followed a generations-old practice of restricting fishing in six areas of their reef lagoon. Their cultural traditions allow line fishing, but no net or spear fishing. Both biomass and individual fish sizes are significantly larger than in places where fishing is unrestricted.
+Increased atmospheric CO2 levels contribute to ocean acidification, which in turn damages coral reefs. To help combat ocean acidification, several countries have enacted laws to reduce greenhouse gas emissions, such as carbon dioxide. Many land use laws aim to reduce CO2 emissions by limiting deforestation. Deforestation can release significant amounts of CO2 unless sequestered through active follow-up forestry programs. Deforestation can also cause erosion, which flows into the ocean, contributing to ocean acidification. Incentives are used to reduce vehicle miles traveled, thereby reducing carbon emissions into the atmosphere and lowering dissolved CO2 in the ocean. State and federal governments also regulate land activities that affect coastal erosion. High-end satellite technology can monitor reef conditions.
+The United States Clean Water Act puts pressure on state governments to monitor and limit run-off of polluted water.
+
+== Restoration ==
+Coral reef restoration has grown in prominence over the past several decades because of the unprecedented reef die-offs around the planet. Coral stressors can include pollution, warming ocean temperatures, extreme weather events, and overfishing. With the deterioration of global reefs, fish nurseries, biodiversity, coastal development, livelihoods, and natural beauty, these are under threat. Fortunately, researchers have taken it upon themselves to develop a new field, coral restoration, in the 1970s–1980s
+
+=== Coral farming ===
+
+Coral aquaculture, also known as coral farming or coral gardening, is showing promise as a potentially effective tool for restoring coral reefs. The "gardening" process bypasses the early growth stages of corals when they are most at risk of dying. Coral seeds are grown in nurseries, then replanted on the reef. Coral is farmed by coral farmers whose interests range from reef conservation to increased income. Due to its straightforward process and substantial evidence of the technique having a significant effect on coral reef growth, coral nurseries became the most widespread and arguably the most effective method for coral restoration.

data/en.wikipedia.org/wiki/Cyclic_steps-0.md

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+---
+title: "Cyclic steps"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Cyclic_steps"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:42.484931+00:00"
+instance: "kb-cron"
+---
+
+Cyclic steps are rhythmic bedforms associated with Froude super-critical flow instability.  They are a type of sediment wave, and are created when supercritical sediment-laden water (turbidity currents) travels downslope through sediment beds.  Each "step" has a steep drop, and together they tend to migrate upstream.  On the ocean floor, this phenomenon was first shown to be possible in 2006, although it was observed in open-channel flows over a decade earlier. Geological features appearing to be submarine cyclic steps have been detected in the northern lowlands of Mars in the Aeolis Mensae region, providing evidence of an ancient Martian ocean.
+
+
+== Formation ==
+
+There are many parameters which govern the formation of cyclic steps: bed slope, bed porosity, erosion resistance, sediment concentration, and flow rate all play a role.  Tilting flumes can be used to create cyclic steps in subaerial laboratory conditions, provided the Froude number is high enough.  If the Froude number is lower than required, then antidunes will form instead.  Additionally, if the sediment is too fine, then chute-and-pool features will form. In subaqueous conditions, most of the work has traditionally been in building mathematical, rather than physical, models of cyclic step formation.  However, cyclic steps have attracted increasing scientific attention in the past decade, and numerous real-world examples of cyclic steps have been found.
+Cyclic steps can be categorized by the rate at which sediment is deposited (the aggradation rate) on different parts of the steps.  The categorization concerns the difference in rate on the stoss (flow-facing) and lee (flow-opposing) sides of the feature.  Type-1 cyclic steps have more lee erosion than there is stoss aggradation, Type-2 have a roughly equal amount of lee erosion and stoss aggradation, and Type-3 has aggradation on both sides.  Type-1 cyclic steps play an important role in canyon formation.  Type-2 cyclic steps have been created in the laboratory, in contrast to Type-3 which is common on the sea floor but is harder to create in laboratory conditions – it was first made experimentally in 2013.  Types 1, 2, and 3 are also called "falling", "transportational", and "climbing", respectively.  Laboratory work has successfully created all three types of cyclic steps in open-channel flows.
+
+
+== Relation to other bedforms ==
+
+In density flows, antidunes can turn into cyclic steps by wave breaking.  Fluid flow is Froude-supercritical over the entirety of antidunes, whereas the flow alternates between the sub- and super-criticality over cyclic steps (with hydraulic jumps between cycles).  Additionally, cyclic steps tend to have a much larger wavelength-to-flow-thickness ratio and a higher suspension index (ratio of shear velocity to sediment settling velocity).  Antidunes are typically unstable (although they can be made stable in laboratory conditions), in contrast to cyclic steps.  Despite these differences, it is not uncommon for researchers to incorrectly label a cyclic step as an antidune.  Cyclic steps also have similarities to chute-and-pool features.  Like cyclic steps, chute-and-pool flows undergo hydraulic jumps, although the flow does not undergo repeated transitions from sub- to super-critical.  When the flow remains subcritical over the whole feature, ripples and dunes form instead.
+
+
+== Examples ==
+
+Attention on real-world cyclic steps has mostly been focused on the ocean floor and at river deltas.  Several submarine cyclic steps have been discovered off the coast of California, such as those in the underwater canyons Monterey Canyon and Eel Canyon.  They have also been discovered in the South China Sea, at the South Taiwan shoal and the West Penghu submarine canyons.  The cyclic step structure at the South Taiwan shoal is the longest ever observed (as of 2015), consisting of 19 steps and ranging over 100 kilometres (62 mi).  They have also been discovered in the Japan Sea at the Toyama deep-sea channel.  On Mars, they have been observed at Aeolis Mensae.  At prodeltas (the portion of a river delta furthest from shore), cyclic steps have been observed in the Mediterranean. The wavelength of prodelta cyclic steps tends to be an order of magnitude smaller than their seafloor counterparts; the Mediterranean cyclic steps have a wavelength ranging from 20 to 100 metres (66 to 328 ft) whereas submarine cyclic steps are typically measured in kilometers.
+While no modern examples have been found, cyclic steps can also form within rivers.  Geologic evidence from the Cambrian-Ordovician Potsdam Group strata indicates that the Quebec Basin once possessed this type of cyclic step.  Glaciolacustrine cyclic steps have also been found in modern Quebec. Cyclic steps can also form along underwater volcanos, such as those in the Punta del Rosario fan,  as well as along carbonate slopes and under bedrock streams.  Cyclic steps do not need to form underwater – wind can cause them too.  Katabatic winds may have caused cyclic steps to form on the ice sheet of Antarctica, and are actively forming cyclic steps at Mars’ poles.
+
+
+== References ==

data/en.wikipedia.org/wiki/Dark_oxygen-0.md

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+---
+title: "Dark oxygen"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Dark_oxygen"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:43.702448+00:00"
+instance: "kb-cron"
+---
+
+Dark oxygen production refers to the generation of molecular oxygen (O2) through processes that do not involve light-dependent oxygenic photosynthesis. The name therefore uses a different sense of 'dark' than that used in the phrase "biological dark matter" (for example) which indicates obscurity to scientific assessment rather than the photometric meaning. While the majority of Earth's oxygen is produced by plants and photosynthetically active microorganisms via photosynthesis, dark oxygen production occurs via a variety of abiotic and biotic processes and may support aerobic metabolism in dark, anoxic environments.
+The theory for dark oxygen production by manganese nodules on the abyssal seafloor is controversial, with scientists disagreeing about its validity.
+
+
+== Abiotic production ==
+Abiotic production of dark oxygen can occur through several mechanisms, such as:
+
+Water radiolysis: This process typically takes place in dark geological ecosystems, such as aquifers, where the decay of radioactive elements in surrounding rock leads to the breakdown of water molecules, producing O2.
+Oxidation of surface-bound radicals: On silicon-bearing minerals like quartz, surface-bound radicals can undergo oxidation, contributing to O2 production.
+In addition to direct O2 formation, these processes often produce reactive oxygen species (ROS), such as hydroxyl radicals (OH•), superoxide (O2•-), and hydrogen peroxide (H2O2). These ROS can be converted into O2 and water either biotically, through enzymes like superoxide dismutase and catalase, or abiotically, via reactions with ferrous iron and other reduced metals.
+
+
+== Biotic production ==
+Biotic production of dark oxygen is performed by microorganisms through distinct microbial processes, including:
+
+Chlorite dismutation: This involves the dismutation of chlorite (ClO2−) into O2 and chloride ions.
+Nitric oxide dismutation: This involves the dismutation of nitric oxide (NO) into O2 and dinitrogen gas (N2) or nitrous oxide (N2O).
+Water lysis via methanobactins: Methanobactins can lyse water molecules to produce O2.
+These processes enable microbial communities to sustain aerobic metabolism in environments that lack oxygen.
+
+
+== Experimental evidence ==
+Recent studies have provided evidence for dark oxygen production in various geological and subsurface environments:
+
+Groundwater ecosystems: Dissolved oxygen concentrations have been measured in old groundwaters previously assumed to be anoxic. The presence of O2 is attributed to microbial communities capable of producing dark oxygen and water radiolysis. Metagenomic analyses and oxygen isotope studies further support local oxygen generation rather than atmospheric mixing.
+Seafloor environments: A study on manganese nodules on the abyssal seafloor has suggested abiotic dark oxygen production. The proposed mechanism is electrolysis, because voltages were recorded on the surface of the nodules. However, no voltage great enough to split water was measured, the energy source for electrolysis is unknown, and previous experiments from the same region have not found any evidence of oxygen production. It has since emerged that manganese nodules were not present in some of the experiments that recorded rising oxygen, and that the result is likely experimental artefact. The authors have since backed away from the two key claims made in the original article - that the rising oxygen levels can be attributed to manganese nodules, and that this is due to the nodules acting like batteries.
+
+
+== Implications ==
+Despite its diverse pathways, dark oxygen production has traditionally been considered negligible in Earth's systems. Recent evidence suggests that O2 is produced and consumed in dark, apparently anoxic environments on a much larger scale than previously thought, with implications for global biogeochemical cycles.
+
+
+== References ==

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+title: "Dead zone (ecology)"
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+tags: "science, encyclopedia"
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+---
+
+Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 mg of O2/liter. When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels. Once DO declines below 0.5 mg O2/liter in a body of water, mass mortality occurs. With such a low concentration of DO, these bodies of water fail to support the aquatic life living there. Historically, many of these sites were naturally occurring.  However, in the 1970s, oceanographers began noting increased instances and expanses of dead zones. These occur near inhabited coastlines, where aquatic life is most concentrated.
+Coastal regions, such as the Baltic Sea, the northern Gulf of Mexico, and the Chesapeake Bay, as well as large enclosed water bodies like Lake Erie, have been affected by deoxygenation due to eutrophication. Excess nutrients are put into these systems by rivers, ultimately from urban and agricultural runoff and exacerbated by deforestation. These nutrients lead to high productivity that produces organic material that sinks to the bottom and is respired. The respiration of that organic material uses up the oxygen and causes hypoxia or anoxia.
+The UN Environment Programme reported 146 dead zones in 2004 in the world's oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometer (0.4 mi2), but the largest dead zone covered 70,000 square kilometers (27,000 mi2). A 2008 study counted 405 dead zones worldwide.
+
+== Causes ==
+
+Aquatic and marine dead zones can be caused by an increase in nutrients (particularly  nitrogen and phosphorus) in the water, known as eutrophication. These nutrients are the fundamental building blocks of single-celled, plant-like organisms that live in the water column, and whose growth is limited in part by the availability of these materials. With more available nutrients, single-celled aquatic organisms (such as algae and cyanobacteria) have the resources necessary to exceed their previous growth limit and begin to multiply at an exponential rate. Exponential growth leads to rapid increases in the density of certain types of these phytoplankton, a phenomenon known as an algal bloom.

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+
+Limnologist David Schindler, whose research at the Experimental Lakes Area led to the banning of harmful phosphates in detergents, warned about algal blooms and dead zones, "The fish-killing blooms that devastated the Great Lakes in the 1960s and 1970s haven't gone away; they've moved west into an arid world in which people, industry, and agriculture are increasingly taxing the quality of what little freshwater there is to be had here....This isn't just a prairie problem. Global expansion of dead zones caused by algal blooms is rising rapidly."
+The major groups of algae are cyanobacteria, green algae, dinoflagellates, coccolithophores and diatom algae. An increase in the input of nitrogen and phosphorus generally causes cyanobacteria to bloom. Other algae are consumed and thus do not accumulate to the same extent as cyanobacteria. Cyanobacteria are not good food for zooplankton and fish and hence accumulate in water, die, and then decompose. The bacterial degradation of their biomass consumes the oxygen in the water, thereby creating the state of hypoxia.
+Dead zones can be caused by natural and by anthropogenic factors. Natural causes include coastal upwelling, changes in wind, and water circulation patterns. Other environmental factors that determine the occurrence or intensity of a dead zone include long water residence times, high temperatures, and high levels of sunlight penetration through the water column.
+Additionally, natural oceanographic phenomena can cause deoxygenation of parts of the water column. For example, enclosed bodies of water, such as fjords or the Black Sea, have shallow sills at their entrances, causing water to be trapped there for a long time. The eastern tropical Pacific Ocean and northern Indian Ocean have lowered oxygen concentrations which are thought to be in regions where there is minimal circulation to replace the oxygen that is consumed. These areas are also known as oxygen minimum zones (OMZ). In many cases, OMZs are permanent or semi-permanent areas.
+Remains of organisms found within sediment layers near the mouth of the Mississippi River indicate four hypoxic events before the advent of synthetic fertilizer. In these sediment layers, anoxia-tolerant species are the most prevalent remains found. The periods indicated by the sediment record correspond to historic records of high river flow recorded by instruments at Vicksburg, Mississippi.
+Changes in ocean circulation triggered by ongoing climate change could also add or magnify other causes of oxygen reductions in the ocean.
+Anthropogenic causes include use of chemical fertilizers and their subsequent presence in water runoff and groundwater, direct sewage discharge into rivers and lakes, and nutrient discharge into groundwater from large, accumulated quantities of animal waste. Use of chemical fertilizers is considered the major human-related cause of dead zones around the world. However, runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication.
+In August 2017, a report suggested that the US meat industry and agroeconomic system are predominantly responsible for the largest-ever dead zone in the Gulf of Mexico.  Soil runoff and leached nitrate, exacerbated by agricultural land management and tillage practices as well as manure and synthetic fertilizer usage, contaminated water from the Heartland to the Gulf of Mexico. A large portion of the plant matter by-products from crops grown in this region are used as major feed components in the production of meat animals for agribusiness companies, like Tyson and Smithfield Foods. Over 86% of the livestock feed is inedible for humans.
+Notable dead zones in the United States include the northern Gulf of Mexico region, surrounding the outfall of the Mississippi River, the coastal regions of the Pacific Northwest, and the Elizabeth River in Virginia Beach, all of which have been shown to be recurring events over the last several years. Around the world, dead zones have developed in continental seas, such as the Baltic Sea, Kattegat, Black Sea, Gulf of Mexico, and East China Sea, all of which are major fishery areas.
+
+== Types ==
+Dead zones can be classified by type, and are identified by the length of their occurrence:
+
+Permanent dead zones are deep water occurrences that rarely exceed 2 milligrams per liter.
+Temporary dead zones are short lived dead zones lasting hours or days.
+Seasonal dead zones are annually occurring, typically in warm months of summer and autumn.
+Diel cycling hypoxia is a specific seasonal dead zone that only becomes hypoxic during the night
+The type of dead zone can, in some ways, be categorized by the time required for the water to return to full health. This time frame depends on the intensity of eutrophication and level of oxygen depletion. A water body that sinks to anoxic conditions and experiences extreme reduction in community diversity will have to travel a much longer path to return to full health. A water body that only experiences mild hypoxia and maintains community diversity and maturity will require a much shorter path length to return to full health.
+
+== Effects ==

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+title: "Dead zone (ecology)"
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+---
+
+The most notable effects of eutrophication are vegetal blooms, sometimes toxic, loss of biodiversity and anoxia, which can lead to the massive death of aquatic organisms.
+Due to the hypoxic conditions present in dead zones, marine life within these areas tends to be scarce. Most fish and motile organisms tend to emigrate out of the zone as oxygen concentrations fall, and benthic populations may experience severe losses when oxygen concentrations are below 0.5 mg l−1 O2. In severe anoxic conditions, microbial life may experience dramatic shifts in community identity as well, resulting in an increased abundance of anaerobic organisms as aerobic microbes decrease in number and switch energy sources for oxidation such as nitrate, sulfate, or iron reduction. Sulfur reduction is a particular concern as hydrogen sulfide is toxic and stresses most organisms within the zone further, exacerbating mortality risks.
+Low oxygen levels can have severe effects on survivability of organisms inside the area while above lethal anoxic conditions. Studies conducted along the Gulf Coast of North America have shown hypoxic conditions lead to reduction of reproductive rates and growth rates in a variety of organisms including fish and benthic invertebrates. Organisms able to leave the area typically do so when oxygen concentrations decrease to less than 2 mg l−1. At these oxygen concentrations and below, organisms that survive inside the oxygen deficient environment and are unable to escape the area will often exhibit progressively worsening stress behavior and die. Surviving organisms tolerant of hypoxic conditions often exhibit physiological adaptations appropriate for persisting within hypoxic environments. Examples of such adaptations include increased efficiency of oxygen intake and use, lowering required amount of oxygen intake through reduced growth rates or dormancy, and increasing the usage of anaerobic metabolic pathways.
+Community composition in benthic communities is dramatically disrupted by periodic oxygen depletion events, such as those of seasonal dead zones and occurring as a result of diel cycles. The longterm effects of such hypoxic conditions result in a shift in communities, most commonly manifest as a decrease in species diversity through mass mortality events. Reestablishment of benthic communities depend upon composition of adjacent communities for larval recruitment. This results in a shift towards faster establishing colonizers with shorter and more opportunistic life strategies, potentially disrupting historic benthic compositions.
+
+=== Fisheries ===
+The influence of dead zones on fisheries and other marine commercial activities varies by the length of occurrence and location. Dead zones are often accompanied by a decrease in biodiversity and collapse in benthic populations, lowering the diversity of yield in commercial fishing operations, but in cases of eutrophication-related dead zone formations, the increase in nutrient availability can lead to temporary rises in select yields among pelagic populations, such as anchovies. However, studies estimate that the increased production in the surrounding areas do not offset the net decrease in productivity resulting from the dead zone. For instance, an estimated 17,000 MT of carbon in the form of prey for fisheries has been lost as a result of dead zones in the Gulf of Mexico. Additionally, many stressors in fisheries are worsened by hypoxic conditions. Indirect factors such as increased success by invasive species and increased pandemic intensity in stressed species such as oysters both lead to losses in revenue and ecological stability in affected regions.
+
+=== Coral reefs ===
+
+There has been a severe increase in mass mortality events associated with low oxygen causing mass hypoxia with the majority having been in the last 2 decades. The rise in water temperature leads to an increase in oxygen demand and the increase for ocean deoxygenation which causes these large coral reef dead zones. For many coral reefs, the response to this hypoxia is very dependent on the magnitude and duration of the deoxygenation. The symptoms can be anywhere from reduced photosynthesis and calcification to bleaching. Hypoxia can have indirect effects like the abundance of algae and spread of coral diseases in the ecosystems. While coral is unable to handle such low levels of oxygen, algae is quite tolerant. Because of this, in interaction zones between algae and coral, increased hypoxia will cause more coral death and higher spread of algae. The increase mass coral dead zones is reinforced by the spread of coral diseases. Coral diseases can spread easily when there are high concentrations of sulfide and hypoxic conditions. Due to the loop of hypoxia and coral reef mortality, the fish and other marine life that inhabit the coral reefs have a change in behavioral in response to the hypoxia. Some fish will go upwards to find more oxygenated water, and some enter a phase of metabolic and ventilatory depression. Invertebrates migrate out of their homes to the surface of substratum or move to the tips of arborescent coral colonies.
+Around six million people, the majority who live in developing countries, depend on coral reef fisheries. These mass die-offs due to extreme hypoxic events can have severe impacts on reef fish populations. Coral reef ecosystems offer a variety of essential ecosystem services including shoreline protection, nitrogen fixation, and waste assimilation, and tourism opportunities. The continued decline of oxygen in oceans on coral reefs is concerning because it takes many years (decades) to repair and regrow corals.

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+title: "Dead zone (ecology)"
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+---
+
+=== Jellyfish blooms ===
+Despite most other life forms being killed by the lack of oxygen, jellyfish can thrive and are sometimes present in dead zones in vast numbers. Jellyfish blooms produce large quantities of mucus, leading to major changes in food webs in the ocean since few organisms feed on them. The organic carbon in mucus is metabolized by bacteria which return it to the atmosphere in the form of carbon dioxide in what has been termed a "jelly carbon shunt".  The potential worsening of jellyfish blooms as a result of human activities has driven new research into the influence of dead zones on jelly populations. The primary concern is the potential for dead zones to serve as breeding grounds for jelly populations as a result of the hypoxic conditions driving away competition for resources and common predators of jellyfish. The increased population of jellyfish could have high commercial costs with loss of fisheries, destruction and contamination of trawling nets and fishing vessels, and lowered tourism revenue in coastal systems.
+
+=== Seagrass beds ===
+Globally, seagrass has been declining rapidly. It is estimated that 21% of the 71 known seagrass species have decreasing population trends and 11% of those species have been designated as threatened on the ICUN Red List. Hypoxia that leads to eutrophication caused from ocean deoxygenation is one of the main underlying factors of these die-offs. Eutrophication causes enhanced nutrient enrichment which can result in seagrass productivity, but with continual nutrient enrichment in seagrass meadows, it can cause excessive growth of microalgae, epiphytes and phytoplankton resulting in hypoxic conditions.
+Seagrass is both a source and a sink for oxygen in the surrounding water column and sediments. At night, the inner part of seagrass oxygen pressure is linearly related to the oxygen concentration in the water column, so low water column oxygen concentrations often result in hypoxic seagrass tissues, which can eventually kill off the seagrass. Normally, seagrass sediments must supply oxygen to the below-ground tissue through either photosynthesis or by diffusing oxygen from the water column through leaves to rhizomes and roots. However, with the change in seagrass oxygen balances, it can often result in hypoxic seagrass tissues. Seagrass exposed to this hypoxic water column show increased respiration, reduced rates of photosynthesis, smaller leaves, and reduced number of leaves per shoot. This causes insufficient supply of oxygen to the belowground tissues for aerobic respiration, so seagrass must rely on the less-efficient anaerobic respiration. Seagrass die-offs create a positive feedback loop in which the mortality events cause more death as higher oxygen demands are created when dead plant material decomposes.
+Because hypoxia increases the invasion of sulfides in seagrass, this negatively affects seagrass through photosynthesis, metabolism and growth. Generally, seagrass is able to combat the sulfides by supplying enough oxygen to the roots. However, deoxygenation causes the seagrass to be unable to supply this oxygen, thus killing it off.
+Deoxygenation reduces the diversity of organisms inhabiting seagrass beds by eliminating species that cannot tolerate the low oxygen conditions. Indirectly, the loss and degradation of seagrass threatens numerous species that rely on seagrass for either shelter or food. The loss of seagrass also effects the physical characteristics and resilience of seagrass ecosystems. Seagrass beds provide nursery grounds and habitat to many harvested commercial, recreational, and subsistence fish and shellfish. In many tropical regions, local people are dependent on seagrass associated fisheries as a source of food and income.
+Seagrass also provides many ecosystem services including water purification, coastal protection, erosion control, sequestration and delivery of trophic subsidies to adjacent marine and terrestrial habitats. Continued deoxygenation causes the effects of hypoxia to be compounded by climate change which will increase the decline in seagrass populations.
+
+=== Mangrove forests ===
+Compared to seagrass beds and coral reefs, hypoxia is more common on a regular basis in mangrove ecosystems, though ocean deoxygenation is compounding the negative effects by anthropogenic nutrient inputs and land use modification.
+Like seagrass, mangrove trees transport oxygen to roots of rhizomes, reduce sulfide concentrations, and alter microbial communities. Dissolved oxygen is more readily consumed in the interior of the mangrove forest. Anthropogenic inputs may push the limits of survival in many mangrove microhabitats. For example, shrimp ponds constructed in mangrove forests are considered the greatest anthropogenic threat to mangrove ecosystems. These shrimp ponds reduce estuary circulation and water quality which leads to the promotion of diel-cycling hypoxia. When the quality of the water degrades, the shrimp ponds are quickly abandoned leaving massive amounts of wastewater. This is a major source of water pollution that promotes ocean deoxygenation in the adjacent habitats.
+Due to these frequent hypoxic conditions, the water does not provide habitats to fish. When exposed to extreme hypoxia, ecosystem function can completely collapse. Extreme deoxygenation will affect the local fish populations, which are an essential food source. The environmental costs of shrimp farms in the mangrove forests grossly outweigh their economic benefits. Cessation of shrimp production and restoration of these areas and reduce eutrophication and anthropogenic hypoxia.
+
+== Locations ==
+In the 1970s, marine dead zones were first noted in settled areas where intensive economic use stimulated scientific scrutiny: in the U.S. East Coast's Chesapeake Bay, in Scandinavia's strait called the Kattegat, which is the mouth of the Baltic Sea and in other important Baltic Sea fishing grounds, in the Black Sea, and in the northern Adriatic.
+Other marine dead zones have appeared in coastal waters of South America, China, Japan, and New Zealand. A 2008 study counted 405 dead zones worldwide.
+
+=== Baltic Sea ===

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+title: "Dead zone (ecology)"
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+---
+
+Researchers from Baltic Nest Institute published in one of PNAS issues reports that the dead zones in the Baltic Sea have grown from approximately 5,000 km2 to more than 60,000 km2 in recent years.
+Some of the causes behind the elevated increase of dead zones can be attributed to the use of fertilizers, large animal farms, the burning of fossil fuels, and effluents from municipal wastewater treatment plants.
+With its massive size, the Baltic Sea is best analyzed in sub-areas rather than as a whole. In a paper published in 2004, researchers specifically divided the Baltic Sea into 9 sub-areas, each having its own specific characteristics. The 9 sub-areas are discerned as follows: Gulf of Bothnia, Archipelago region, Gulf of Finland, Gulf of Riga, Gulf of Gdansk, Swedish East-coast, Central Baltic, Belt Sea region, and Kattegat. Each sub-area has responded differently to nutrient additions and eutrophication; however, there are a few general patterns and measures for the Baltic Sea as a whole. As the researchers Rönnberg and Bonsdorff state,
+"Irrespective of the area-specific effects of the increased loads of nutrients to the Baltic Sea, the sources are more or less similar in the whole region. The extent and the severity of the discharges may differ, however. As is seen in e.g. HELCOM (1996) and Rönnberg (2001), the major sources in the input of nutrients are derived from agriculture, industry, municipal sewage and transports. Nitrogen emissions in form of atmospheric depositions are also important, as well as local point sources, such as aquaculture and leakage from forestry."
+In general, each area of the Baltic Sea is experiencing similar anthropogenic effects. As Rönnberg and Bonsdorff state, "Eutrophication is a serious problem in the Baltic Sea area." However, when it comes to implementation of water revival programs, each area likely will need to be handled on a local level.
+
+=== Virginia ===
+
+==== Chesapeake Bay ====
+According to the National Geographic, the Chesapeake Bay was one of the first hypoxic zones to be identified in the 1970s. The Chesapeake Bay experiences seasonal hypoxia due to high nitrogen levels. These nitrogen levels are caused by urbanization, there are multiple factories that pollute the atmosphere with nitrogen, and agriculture, the opposite side of the bay is used for poultry farming, which produces a lot of manure that ends up running off into the Chesapeake Bay.
+From 1985–2019, there were efforts from the caretakers of Chesapeake Bay to reduce the annual hypoxic volumes. There was significant improvement in 2016–2017 that gave assurance to the caretakers that the efforts were successful, however recent data has shown that further efforts are needed to continuously curb the effects of global warming.
+
+==== Elizabeth River, Virginia ====
+The Elizabeth River estuary is used for commercial and military use and is one of the most commonly used ports on the East Coast of the USA. From 2015-2019, 11 different conditions were measured in various areas of the Elizabeth River. Throughout the river, there were consistently high levels of nitrogen and phosphorus, along with high levels of other contaminants contributing to the poor quality of life for bottom feeders along the river. The main cause of the pollution to the Elizabeth river has been the military and industrial activities through the 1990s. In 1993, the Elizabeth River Project was started in attempt to do a restoration project on the river. Adopting one of the fish whose species had been largely impacted by the pollution, the Fundulus heteroclitus (Mummichog), the group was able to gain traction and carry out multiple projects and has removed thousands of tons of contaminated sediment. In 2006, Maersk-APM, a major shipping company, wanted to build a new port on the Elizabeth River. As part of the environmental mitigation they worked with the Elizabeth River Project to create the Money Point Project, which was an effort to restore Money Point, which had been deemed biologically depleted due to a black tar like substance called creosote laying at the bottom. Maersk-APM gave $5 million to help get the project up and running. By 2012, they were able to restore over 7 acres of tidal marsh, 3 acres of oyster reef and created a new shoreline. In 2019, the Money Point Project received the "Best Restored Shore" award from the American Shore and Beach Preservation Association.
+
+=== Lake Erie ===
+A seasonal dead zone exists in the central part of Lake Erie from east of Point Pelee to Long Point and stretches to shores in Canada and the United States. Between the months of July and October the dead zone has the ability to grow to the size of 10,000 square kilometers. Lake Erie has an excess of phosphorus due to agricultural runoff that quickens the growth of algae which then contributes to hypoxic conditions. The superabundance of phosphorus in the lake has been linked to nonpoint source pollution such as urban and agricultural runoff as well as point source pollution that includes sewage and wastewater treatment plants. The zone was first noticed in the 1960s amid the peak of eutrophication occurring in the lake. After public concern increased, Canada and the US launched efforts to reduce runoff pollution into the lake in the 1970s as means to reverse the dead zone growth. Scientists in 2018 stated that phosphorus runoff would have to further decrease by 40% to avoid the emergence of the dead zones in the area. The commercial and recreational fishing industry have been significantly impacted by the hypoxic zone. In 2021, the low-oxygenated waters caused a mass-kill event of freshwater drum fish species (also known as sheepshead fish). Water from the lake is also used for human drinking. Water from the lake has been said to acquire a pervasive odor and discoloration when the dead zone is active in the late summer months.

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+title: "Dead zone (ecology)"
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+---
+
+=== Lower St. Lawrence Estuary ===
+A dead zone exists in the Lower St. Lawrence River area from east the Saguenay River to east of Baie Comeau, greatest at depths over 275 metres (902 ft) and noticed since the 1930s. The main concern for Canadian scientists is the impact on fish found in the area.
+
+=== Oregon ===
+There is a hypoxic zone covering the coasts of Oregon and Washington that reached peak size in 2006 at an area of over 1,158 square miles. Strong surface winds between April and September cause frequent upwelling that results in an increase of algae blooms, rendering the hypoxia a seasonal occurrence. The upwelling has contributed to lower temperatures within the zone. The dead zone has resulted in sea organisms such as crabs and fish relocating and an interference with commercial fishing. Organisms that cannot relocate have been found to suffocate, leaving them useless for fishermen. In 2009, one scientist described "thousands and thousands" of suffocated, crabs, worms, and sea stars along the seafloor of the hypoxic zone. In 2021, 1.9 million dollars were put into monitoring and continuing to study the hypoxic conditions in the area that the dead zone occurs in.
+
+=== Gulf of Mexico 'dead zone' ===
+
+The area of temporary hypoxic bottom water that occurs most summers off the coast of Louisiana in the Gulf of Mexico is the largest recurring hypoxic zone in the United States. It occurs only during the summer months of the year due to summer warming, regional circulation, wind mixing and high freshwater discharge.  The Mississippi River, which is the drainage area for 41% of the continental United States, dumps high-nutrient runoff such as nitrates and phosphorus into the Gulf of Mexico. According to a 2009 fact sheet created by NOAA, "seventy percent of nutrient loads that cause hypoxia are a result of this vast drainage basin", which includes the heart of U.S. agribusiness, the Midwest. The discharge of treated sewage from urban areas (pop. c 12 million in 2009) combined with agricultural runoff deliver c. 1.7 million tons of phosphorus and nitrogen into the Gulf of Mexico every year. Nitrogen is indeed needed to increase crop yields, but plants are inefficient at taking it up, and often more fertilizers are used than plants actually need.  Therefore, only a percentage of applied nitrogen ends up in the crops; and in some areas that number is less than 20%.   Even though Iowa occupies less than 5% of  the Mississippi River drainage basin, average annual nitrate discharge from surface water in Iowa is about 204,000 to 222,000 metric tonnes, or 25% of all the nitrate that the Mississippi River delivers to the Gulf of Mexico. Export from the Raccoon River Watershed is among the highest in the United States, with annual yields at 26.1 kg/ha/year, which ranked as the highest loss of nitrate out of 42 Mississippi subwatersheds evaluated for a Gulf of Mexico hypoxia report.  In 2012, Iowa introduced the Iowa Nutrient Reduction Strategy, which "is a science and technology-based framework to assess and reduce nutrients to Iowa waters and the Gulf of Mexico. It is designed to direct efforts to reduce nutrients in surface water from both point and nonpoint sources in a scientific, reasonable and cost effective manner."  The strategy continues to evolve, using voluntary methods to reduce Iowa's negative contributions through outreach, research, and implementation of nutrient holding practices. In order to help reduce agricultural runoff into the Mississippi Basin, Minnesota passed MN Statute 103F.48 in 2015, also known as the "Buffer Law", which was designed to implement mandatory riparian buffers between farmland and public waterways across the State of Minnesota. The Minnesota Board of Water and Soil Resources (BWSR) issued a January 2019 report stating that compliance with the 'Buffer Law' has reached 99%.
+
+==== Size ====
+The area of hypoxic bottom water that occurs for several weeks each summer in the Gulf of Mexico has been mapped most years from 1985 through 2024.  The size varies annually from a record high in 2017 when it encompassed more than 22,730 square kilometers (8,776 square miles) to a record low in 1988 of 39 square kilometers (15 square miles).
+
+The 2015 dead zone measured 16,760 square kilometers (6,474 square miles).
+Nancy Rabalais of the Louisiana Universities Marine Consortium in Cocodrie, Louisiana predicted the dead zone or hypoxic zone in 2012 will cover an area of 17,353 square kilometers (6,700 square miles) which is larger than Connecticut; however, when the measurements were completed, the area of hypoxic bottom water in 2012 only totaled 7,480 square kilometers. The models using the nitrogen flux from the Mississippi River to predict the "dead zone" areas have been criticized for being systematically high from 2006 to 2014, having predicted record areas in 2007, 2008, 2009, 2011, and 2013 that were never realized.
+In late summer 1988 the dead zone disappeared as the great drought caused the flow of Mississippi to fall to its lowest level since 1933. During times of heavy flooding in the Mississippi River Basin, as in 1993, "the "dead zone"
+dramatically increased in size, approximately 5,000 km (3,107 mi) larger than the previous year".

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+title: "Dead zone (ecology)"
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+---
+
+==== Economic impact ====
+Some assert that the dead zone threatens lucrative commercial and recreational fisheries in the Gulf of Mexico. "In 2009, the dockside value of commercial fisheries in the Gulf was $629 million. Nearly three million recreational fishers further contributed about $10 billion to the Gulf economy, taking 22 million fishing trips." The seafood production is not only hurting states located on the Gulf of Mexico but the U.S. as a whole. It is reported that the Gulf of Mexico dead zone is costing the U.S. seafood and tourism industries about $82 million a year. Louisiana is ranked second in seafood production behind Alaska, and this impact can be devastating for the nations seafood production since the Gulf of Mexico sources 40% of the nations seafood. Scientists are not in universal agreement that nutrient loading has a negative impact on fisheries. Grimes makes a case that nutrient loading enhances the fisheries in the Gulf of Mexico. Courtney et al. hypothesize that nutrient loading may have contributed to the increases in red snapper in the northern and western Gulf of Mexico.
+In 2017, Tulane University offered a $1 million challenge grant for growing crops with less fertilizer.
+
+==== History ====
+Shrimp trawlers first reported a 'dead zone' in the Gulf of Mexico in 1950, but it was not until 1970 when the size of the hypoxic zone had increased that scientists began to investigate.
+After 1950, the conversion of forests and wetlands for agricultural and urban developments accelerated. "Missouri River Basin has had hundreds of thousands of acres of forests and wetlands (66,000,000 acres) replaced with agriculture activity [. . .] In the Lower Mississippi one-third of the valley's forests were converted to agriculture between 1950 and 1976."
+In July 2007, a dead zone was discovered off the coast of Texas where the Brazos River empties into the Gulf.
+
+=== Korea ===
+
+==== Jinhae Bay ====
+Jinhae Bay is the first of Korea's two major dead zones. Hypoxia was first reported in Jinhae Bay in September 1974. In 2011, a joint study was done to observe and record causes, effects, and what can be done about Korea's hypoxic zones. It was discovered that Jinhae Bay exhibits a seasonal dead zone from early June to late September. This dead zone is caused by "domestic and land use waste and thermal stratification". Jinhae Bay experiences hypoxia largely at the bottom of its bay. The ratio of phosphorus to nitrogen is imbalanced at the bottom, where it is otherwise balanced at the top, with the exception of early June to late September where the Bay experiences eutrophication as a whole. The effects of Jinhae Bay's hypoxia is seen in the marine system surrounding Korea, with a loss of biological diversity, particularly of the calcareous shelled organisms.
+
+==== Shihwa Bay ====
+Shihwa Bay is a coastal reservoir created in 1994 to supply surrounding agricultural lands with water, and act as a run-off lake for nearby industrial plants. The Bay was made without much environmental consideration, and by 1999, water quality saw a significant drop. This drop in water quality is attributed to the bay not having enough circulation or new water flow to accommodate the domestic and industrial waste being dumped. In response, the Korean government set up a pollution management system within the bay, and has installed a gate system that allows the Bay to mix with water from the sea. Shihwa Bay is also experiencing an imbalance of phosphorus to nitrogen, but also large influxes of ammonium.
+
+== Energy Independence and Security Act of 2007 ==
+The Energy Independence and Security Act of 2007 calls for the production of 36 billion US gallons (140,000,000 m3) of renewable fuels by 2022, including 15 billion US gallons (57,000,000 m3) of corn-based ethanol, a tripling of current production that would require a similar increase in corn production. Unfortunately, the plan poses a new problem; the increase in demand for corn production results in a proportional increase in nitrogen runoff. Although nitrogen, which makes up 78% of the Earth's atmosphere, is an inert gas, it has more reactive forms, two of which (nitrate and ammonia) are used to make fertilizer.
+According to Fred Below, a professor of crop physiology at the University of Illinois at Urbana-Champaign, corn requires more nitrogen-based fertilizer because it produces a higher grain per unit area than other crops and, unlike other crops, corn is completely dependent on available nitrogen in soil. The results, reported March 18, 2008, in Proceedings of the National Academy of Sciences, showed that scaling up corn production to meet the 15-billion-US-gallon (57,000,000 m3) goal would increase nitrogen loading in the Dead Zone by 10–18%. This would boost nitrogen levels to twice the level recommended by the Mississippi Basin/Gulf of Mexico Water Nutrient Task Force (Mississippi River Watershed Conservation Programs), a coalition of federal, state, and tribal agencies that have monitored the dead zone since 1997. The task force says a 30% reduction of nitrogen runoff is needed if the dead zone is to shrink.

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+title: "Dead zone (ecology)"
+chunk: 8/10
+source: "https://en.wikipedia.org/wiki/Dead_zone_(ecology)"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:44.955451+00:00"
+instance: "kb-cron"
+---
+
+== Prediction and Use of AI for Dead Zones ==
+Dead zones are hard to predict since they use multiple environmental factors. They use nutrient runoff, rainfall, water temperature, and dissolved oxygen levels. Due to this, traditional modeling uses field sampling and satellite observations in order to see major changes. Though this does not measure rapid change, it won't be able to see complete coverage of major areas. Due to this issue, there has been research using artificial intelligence (AI) and machine learning models to increase prediction accuracy and areas that are at risk. This can help see what areas risk of hypoxia before it develops. 
+AI can examine large environmental databases to recognize patters associated with dead zone formations. Machine learning algorithms process information like nitrogen and phosphorus concentrations, precipitation rates, and more, to estimate where low oxygen conditions occur and when. These systems come in handy when monitoring data are incomplete or unavailable allowing researchers to estimate missing data and improve prediction rates.
+Researchers at Louisiana state University have developed AI-based tools to predict nutrient pollution in watersheds connected to Gulf of Mexico. These tools use machine learning to estimate nutrient runoff from rivers and agriculture land. This helps scientists understand how excess nitrogen and phosphorus contribute to hypoxic zones. AI models help with looking into relationships between land use, rain fall, and nutrient transport that may not be detected through traditional testing methods. 
+Machine learning has also been applied to large freshwater ecosystems like Lake Erie, they used predicative models to monitor harmful algal blooms and oxygen depletion. AI driven sensors and remote monitoring systems collect real time environmental data to forecast the intensity of algal bloom. Agal bloom is connected to dead zones and also nutrient pollution, this helps early detection and helps researchers respond before hypoxia occurs.
+AI may improve the environmental management by supporting faster and accurate predictions. This also helps a reduction of prioritizing nutrients in areas without risk and managing it better. However, AI models still depend on high quality datasets and may be limited by incomplete environmental records or changing climate condition due to the rise of climate change. Research is still being conducted but hope for the future.
+
+== Reversal ==
+
+The recovery of benthic communities primarily depends upon the length and severity of hypoxic conditions inside the zone. Less severe conditions and temporary depletion of oxygen allow rapid recovery of benthic communities in the area due to reestablishment by benthic larvae from adjacent areas, with longer conditions of hypoxia and more severe oxygen depletion leading to longer reestablishment periods. Recovery also depends upon stratification levels within the area, so heavily stratified areas in warmer waters are less likely to recover from anoxic or hypoxic conditions in addition to being more susceptible to eutrophication driven hypoxia. The difference in recovery ability and susceptibility to hypoxia in stratified marine environments is expected to complicate recovery efforts of dead zones in the future as ocean warming continues.
+Small scale hypoxic systems with rich surrounding communities are the most likely to recover after nutrient influxes leading to eutrophication stop. However, depending on the extent of damage and characteristics of the zone, large scale hypoxic condition could also potentially recover after a period of a decade. For example, the Black Sea dead zone, previously the largest in the world, largely disappeared between 1991 and 2001 after fertilizers became too costly to use following the collapse of the Soviet Union and the demise of centrally planned economies in Eastern and Central Europe. Fishing has again become a major economic activity in the region.
+While the Black Sea "cleanup" was largely unintentional and involved a drop in hard-to-control fertilizer usage, the U.N. has advocated other cleanups by reducing large industrial emissions. From 1985 to 2000, the North Sea dead zone had nitrogen reduced by 37% when policy efforts by countries on the Rhine River reduced sewage and industrial emissions of nitrogen into the water. Other cleanups have taken place along the Hudson River and San Francisco Bay.

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+title: "Dead zone (ecology)"
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+category: "reference"
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+date_saved: "2026-05-05T07:34:44.955451+00:00"
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+---
+
+== Biotechnology Application ==
+There are some options that can aid in the reversal process of a dead zone and eventual recovery of water quality and benthic communities through applied biotechnology methodology if a given management project can apply it if the conditions of a dead-zone fit within the criteria. One of the more natural options is established filter feeding species within a marine community that are nearby a impacted ecological area transitioned into a dead zone that can then spread and possibly establish a population there in which recovery time can vary as they filter out access nitrogen and phosphorus. Given that many filter feeding species have different tolerance levels due to the extreme hypoxic conditions, it can be determined through research of how various species respond behaviorally to those specific conditions and deduce the most appropriate species based on a dead-zone of interest to recover. An 8-day study was done on eastern oysters (Crassostrea virginica) and soft-shell clams (Mya arenaria) to assess their reactions to hypoxic and heatwave conditions. While this study was meant for establishing an understanding of behavioral patterns in warming conditions for filter-feeding species, this type of approach can be conducted on other filter-feeding species to assess their potential as a significant part of the recovery process for select dead-sea communities for potential introduction.
+An additional approach is establishing dedicated biofilter zones within a dead-zone area to trigger the recovery process in a faster and more controlled environment to enable the management recovery process in a stronger way. A long-term study was executed in response to rising concerns in nitrogen pollution in marine ecosystems, so a anammox bio filter reactor was made for this study to assess bacterial nitrogen removal capabilities. "Anammox efficiently converts two pivotal nitrogen compounds, NH4+ (electron donor) and NO2− (electron acceptor), into dinitrogen gas, circumventing the limitations of conventional nitrification–denitrification pathways. This makes it one of the most cost-effective and efficient methods for biological nitrogen removal (Zhu et al., 2023)." Overall it was present that when dead zones would emerge, biofilms would trigger these nitrogen-removing bacteria through signal molecule regulation and microbial succession to adapt to environmental stress and maintain long-term bio filter reactor stability.
+Biomineralization is a pretty effective biotechnical approach as well, as the way it works is organic matter pulls in inorganic matter/nutrients through a process that forms mineral structures. This process is most commonly bio-technically executed using micro-organisms for a wide variety of uses. However it can be induced in several ways as the way it interacts in a marine environment with microorganisms is mainly pulling in phosphorus and carbon and crystalizing, once it reaches a certain weight it make sink and or able to be collected using wastewater management procedures. This study used a anaerobic membrane bioreactor combined with iron-induced biomineralization to treat swine wastewater which proved to be highly successful. Put this in a dead-zone context and implementing biomineralization by inducing it in whichever way best fits as it doesn't just have to be phosphorus, it can be nitrogen or carbon focused biomineralization depending on how the method is executed which can then make the clean-up recovery process of access phosphorus in a dead-zone easier to clean. These biotechnology application prompts have not been executed as dedicated applications to aid in the recovery process of a dead-zone but there is potential as more research is put into some of these types of techniques and their success is measured over time.
+
+== Modelling ==
+Mathematical and computational models are a critical component in the study of dead zones. Using these models with dead zones will help policy makers predict the impacts various factors have when it comes to dead zones. Modelling has been used to take nutrient inputs (nitrogen and phosphorus) across water bodies then predicts what the inputs will do in regaurds to algal blooms and oxygen depletion. There is also modelling in dead zones utilizing prediction skills by inserting nitrogen and phosphorus application to a field and predicts the runoff and nutrient leaching amounts that will occur in the nearby water bodies.
+
+== See also ==
+
+== Notes ==
+
+== References ==
+Diaz, R. J.; Rosenberg, R. (August 15, 2008). "Spreading Dead Zones and Consequences for Marine Ecosystems". Science. 321 (5891): 926–929. Bibcode:2008Sci...321..926D. doi:10.1126/science.1156401. PMID 18703733. S2CID 32818786.
+Osterman, Lisa E.; Poore, Richard Z.; Swarzenski, Peter W.; Turner, R. Eugene (2005). "Reconstructing a 180 yr record of natural and anthropogenic induced low-oxygen conditions from Louisiana continental shelf sediments". Geology. 33 (4): 329. Bibcode:2005Geo....33..329O. doi:10.1130/G21341.1. S2CID 55361042.
+Taylor, F. J.; Taylor, N. J.; Walsby, J. R. (1985). "A Bloom of the Planktonic Diatom, Cerataulina pelagica, off the Coast of Northeastern New Zealand in 1983, and its Contribution to an Associated Mortality of Fish and Benthic Fauna". Internationale Revue der gesamten Hydrobiologie und Hydrographie. 70 (6): 773–795. Bibcode:1985IRH....70..773T. doi:10.1002/iroh.19850700602.
+Morrisey, D.J; Gibbs, M.M; Pickmere, S.E; Cole, R.G (May 2000). "Predicting impacts and recovery of marine-farm sites in Stewart Island, New Zealand, from the Findlay–Watling model". Aquaculture. 185 (3–4): 257–271. Bibcode:2000Aquac.185..257M. doi:10.1016/s0044-8486(99)00360-9.
+Potera, Carol (June 2008). "Fuels: Corn Ethanol Goal Revives Dead Zone Concerns". Environmental Health Perspectives. 116 (6): A242-3. doi:10.1289/ehp.116-a242. PMC 2430248. PMID 18560496.
+Minnesota Board of Water and Soil Resources (BWSR, 2018), Alternative Practices Introduction | MN Board of Water, Soil Resources
+Minnesota 'Buffer Law' statute: MN Statute 103F.48
+BWSR Update, January 2019: [1] Archived February 16, 2019, at the Wayback Machine
+Ronnberg, C., & Bonsdorff, E. (February 2004). Baltic Sea eutrophication: area-specific ecological consequences [Article; Proceedings Paper]. Hydrobiologia, 514(1–3), 227–241. https://doi.org/10.1023/B:HYDR.0000019238.84989.7f
+Le Moal, Morgane, Gascuel-Odoux, Chantal, Ménesguen, Alain, Souchon, Yves, Étrillard, Levain, Alix, ... Pinay, Gilles (2019). Eutrophication: A new wine in an old bottle? Elsevier, Science of the Total Environment 651:1–11.

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+title: "Dead zone (ecology)"
+chunk: 10/10
+source: "https://en.wikipedia.org/wiki/Dead_zone_(ecology)"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:44.955451+00:00"
+instance: "kb-cron"
+---
+
+== Further reading ==
+Growing 'dead zone' Confirmed by Underwater Robots in the Gulf of Oman, phys.org, April 2018
+Hendy, Ian (August 2017), Gulf of Mexico 'dead zone' is already a disaster – but it could get worse, The Conversation
+Bryant, Lee (April 2015), Ocean 'dead zones' are spreading – and that spells disaster for fish, The Conversation
+Deprecated link at archive.today (archived January 29, 2013)
+Suzie Greenhalgh and Amanda Sauer (WRI), "Awakening the 'Dead Zone': An investment for agriculture, water quality, and climate change" 2003
+Reyes Tirado (July 2008) Dead Zones: How Agricultural Fertilizers are Killing our Rivers, Lakes and Oceans. Greenpeace publications. See also: "Dead Zones: How Agricultural Fertilizers are Killing our Rivers, Lakes and Oceans". Greenpeace Canada. July 7, 2008. Archived from the original on September 8, 2010. Retrieved August 3, 2010.
+MSNBC report on dead zones, March 29, 2004
+Joel Achenbach, "A 'Dead Zone' in The Gulf of Mexico: Scientists Say Area That Cannot Support Some Marine Life Is Near Record Size", The Washington Post, July 31, 2008
+Joel Achenbach, "'Dead Zones' Appear In Waters Worldwide: New Study Estimates More Than 400", The Washington Post, August 15, 2008
+
+== External links ==
+Louisiana Universities Marine Consortium
+UN Geo Yearbook 2003 report on nitrogen and dead zones at the Library of Congress Web Archives (archived August 2, 2005)
+NASA on dead zones (Satellite pictures) Archived November 23, 2015, at the Wayback Machine
+Gulf of Mexico Dead Zone – multimedia
+Gulf of Mexico Hypoxia Watch, NOAA, Joel Achenbach at the Wayback Machine (archived October 9, 2007)
+NutrientNet at the Wayback Machine (archived July 11, 2010), an online nutrient trading tool developed by the World Resources Institute, designed to address issues of eutrophication. See also the PA NutrientNet website designed for Pennsylvania's nutrient trading program.

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+---
+title: "Deep-sea fish"
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+
+Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep-sea fishes include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, viperfish, and some species of eelpout.
+Only about 2% of known marine species inhabit the pelagic environment. This means that they live in the water column as opposed to the benthic organisms that live in or on the sea floor. Deep-sea organisms generally inhabit bathypelagic (1–4 km; 0.62–2.49 mi deep) and abyssopelagic (4–6 km; 2.5–3.7 mi deep) zones. However, characteristics of deep-sea organisms, such as bioluminescence can be seen in the mesopelagic (200–1,000 m; 660–3,280 ft deep) zone as well. The mesopelagic zone is the disphotic zone, meaning light there is minimal but still measurable. The oxygen minimum layer exists somewhere between a depth of 700 and 1,000 metres (2,300 and 3,300 ft) depending on the place in the ocean. This area is also where nutrients are most abundant. The bathypelagic and abyssopelagic zones are aphotic, meaning that no light penetrates this area of the ocean. These zones make up about 75% of the inhabitable ocean space.
+The epipelagic zone (0–200 metres or 0–650 ft deep) is the area where light penetrates the water and photosynthesis occurs. This is also known as the photic zone. Because this typically extends only a few hundred meters below the water, the deep sea, about 90% of the ocean volume, is in darkness. The deep sea is also an extremely hostile environment, with temperatures that rarely exceed 3 °C (37 °F) and fall as low as −1.8 °C (29 °F) (with the exception of hydrothermal vent ecosystems that can exceed 350 °C, or 662 °F), low oxygen levels, and pressures between 20 and 1000 atm (2-100 MPa, 300–14,500 psi).
+
+== Evolution ==
+It has been speculated that deep-sea ecosystems may have been inhospitable to vertebrate life prior to an increased influx of nutrients into the ocean during the Late Jurassic and Early Cretaceous following the rise of angiosperms on land, which led to an increase in abyssal invertebrate life, allowing fish to in turn colonize these ecosystems. However, some modern deep-sea fish, such as holocephalians, are descendants of much older lineages, indicating that much earlier colonizations of the deep-sea by vertebrates may have occurred, although no fossil evidence of this is known.
+The earliest known records of deep-sea fish are trace fossils of feeding and swimming behavior attributed to unidentified neoteleosts (referable to the ichnogenera Piscichnus and Undichna), from the Early Cretaceous (130 million-year-old) Palombini Shale of Italy, which is thought to have been deposited in the abyssal plain of the former Piemont-Liguria Ocean. Prior to the discovery of these fossils, there was no evidence for deep-sea bony fish older than 50 million years in the Paleogene. The Cretaceous origin for most modern deep-sea fish has been further affirmed with phylogenetic studies such as those of aulopiform fish, which indicate that many deep-sea lineages of these groups originated around this time.
+Although the records from the Palombini Shale represent the earliest records of deep-sea bony fish, formations that preserve deepwater shark fossils are also known from later in the Cretaceous. These include the Northumberland Formation of Canada and similarly aged deposits in Angola, both of which preserve fossils of taxa such as hexanchids, chlamydoselachids, and catsharks, which are known from deepwater habitats today but rare in other formations of the time. Paleogene formations with fossil deep-sea shark teeth are known from New Zealand for the middle Paleocene, and formations in Denmark, France, Austria, and Morocco during the Eocene. The Paratethys Sea still supported deepwater sharks and rays into the Miocene, which are preserved in formations in Hungary.
+During the Paleogene, some prominent formations that preserve well-articulated specimens of deep-sea bony fish are known. These include the Monte Solane lagerstatte of early Eocene Italy, which preserves a bathypelagic habitat likely deposited 300–600 meters (980–1,970 ft) under the sea, as well as the late Eocene Pabdeh Formation of Iran. The deep-sea environments preserved by both formations are apparent through their abundance of fossil stomiiform fish. Notable Neogene formations that preserve fossils of deep-sea bony fish are known from the Miocene of Italy, Japan, and California.
+
+== Environment ==

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+---
+title: "Deep-sea fish"
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+category: "reference"
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+
+In the deep ocean, the waters extend far below the epipelagic zone, and support very different types of pelagic fishes adapted to living in these deeper zones. In deep water, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. Its origin lies in activities within the productive photic zone. Marine snow includes dead or dying plankton, protists (diatoms), fecal matter, sand, soot and other inorganic dust. The "snowflakes" grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres (3,300 ft) of their journey, that is, within the epipelagic zone. In this way, marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: as sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. Since there is no light in the deep sea (aphotic), there is a lack of primary producers. Therefore, most organisms in the bathypelagic rely on the marine snow from regions higher in the vertical column.
+Some deep-sea pelagic groups, such as the lanternfish, ridgehead, marine hatchetfish, and lightfish families, are sometimes termed pseudoceanic because, rather than having an even distribution in open water, they occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes. The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures.
+Hydrostatic pressure increases by 1 atm (0.1 MPa) for every 10 m (33 ft) in depth. Deep-sea organisms have the same pressure within their bodies as is exerted on them from the outside, so they are not crushed by the extreme pressure. Their high internal pressure, however, results in the reduced fluidity of their membranes because molecules are squeezed together. Fluidity in cell membranes increases efficiency of biological functions, most importantly the production of proteins, so organisms have adapted to this circumstance by increasing the proportion of unsaturated fatty acids in the lipids of the cell membranes. In addition to differences in internal pressure, these organisms have developed a different balance between their metabolic reactions from those organisms that live in the epipelagic zone. David Wharton, author of Life at the Limits: Organisms in Extreme Environments, notes "Biochemical reactions are accompanied by changes in volume. If a reaction results in an increase in volume, it will be inhibited by pressure, whereas, if it is associated with a decrease in volume, it will be enhanced". This means that their metabolic processes must ultimately decrease the volume of the organism to some degree.
+
+Most fish that have evolved in this harsh environment are not capable of surviving in laboratory conditions, and attempts to keep them in captivity have led to their deaths. Deep-sea organisms contain gas-filled spaces (vacuoles). Gas is compressed under high pressure and expands under low pressure. Because of this, these organisms have been known to blow up if they come to the surface.
+
+== Characteristics ==

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+
+The fish of the deep-sea have evolved various adaptations to survive in this region. Since many of these fish live in regions where there is no natural illumination, they cannot rely solely on their eyesight for locating prey and mates and avoiding predators; deep-sea fish have evolved appropriately to the extreme sub-photic region in which they live. Many of these organisms are blind and rely on their other senses, such as sensitivities to changes in local pressure and smell, to catch their food and avoid being caught. Those that aren't blind have large and sensitive eyes that can use bioluminescent light. These eyes can be as much as 100 times more sensitive to light than human eyes. Rhodopsin (Rh1) is a protein found in the eye's rod cells that helps animals see in dim light. While most vertebrates usually have one Rh1 opsin gene, some deep-sea fish have several Rh1 genes, and one species, the silver spinyfin (Diretmus argenteus), has 38. This proliferation of Rh1 genes may help deep-sea fish to see in the depths of the ocean. Also, to avoid predation, many species are dark to blend in with their environment.
+Many deep-sea fish are bioluminescent, with extremely large eyes adapted to the dark. Bioluminescent organisms are capable of producing light biologically through the agitation of molecules of luciferin, which then produce light. This process must be done in the presence of oxygen. These organisms are common in the mesopelagic region and below (200 metres (656 ft) and below). More than 50% of deep-sea fish, as well as some species of shrimp and squid, are capable of bioluminescence. About 80% of these organisms have photophores – light producing glandular cells that contain luminous bacteria bordered by dark colourings. Some of these photophores contain lenses, much like those in the eyes of humans, which can intensify or lessen the emanation of light. The ability to produce light only requires 1% of the organism's energy and has many purposes: It is used to search for food and attract prey, like the anglerfish; claim territory through patrol; communicate and find a mate, and distract or temporarily blind predators to escape. Also, in the mesopelagic where some light still penetrates, some organisms camouflage themselves from predators below them by illuminating their bellies to match the colour and intensity of light from above so that no shadow is cast. This tactic is known as counter-illumination.
+The lifecycle of deep-sea fish can be exclusively deep-water, although some species are born in shallower water and sink upon maturation. Regardless of the depth where eggs and larvae reside, they are typically pelagic. This planktonic — drifting — lifestyle requires neutral buoyancy. In order to maintain this, the eggs and larvae often contain oil droplets in their plasma. When these organisms are in their fully matured state they need other adaptations to maintain their positions in the water column. In general, water's density causes upthrust — the aspect of buoyancy that makes organisms float. To counteract this, the density of an organism must be greater than that of the surrounding water. Most animal tissues are denser than water, so they must find an equilibrium to make them float. Many organisms develop swim bladders (gas cavities) to stay afloat, but because of the high pressure of their environment, deep-sea fishes usually do not have this organ. Instead they exhibit structures similar to hydrofoils in order to provide hydrodynamic lift. It has also been found that the deeper a fish lives, the more jelly-like its flesh and the more minimal its bone structure. They reduce their tissue density through high fat content, reduction of skeletal weight — accomplished through reductions of size, thickness and mineral content — and water accumulation makes them slower and less agile than surface fish. The body shapes of deep-sea fish are generally better adapted for periodic bursts of swimming rather than constant swimming.
+Due to the poor level of photosynthetic light reaching deep-sea environments, most fish need to rely on organic matter sinking from higher levels, or, in rare cases, hydrothermal vents for nutrients. This makes the deep-sea much poorer in productivity than shallower regions. Also, animals in the pelagic environment are sparse and food doesn't come along frequently. Because of this, organisms need adaptations that allow them to survive. Some have long feelers to help them locate prey or attract mates in the pitch black of the deep ocean. The deep-sea angler fish in particular has a long fishing-rod-like adaptation protruding from its face, on the end of which is a bioluminescent piece of skin that wriggles like a worm to lure its prey. Some must consume other fish that are the same size or larger than them and they need adaptations to help digest them efficiently. Great sharp teeth, hinged jaws, disproportionately large mouths, and expandable bodies are a few of the characteristics that deep-sea fishes have for this purpose. The gulper eel is one example of an organism that displays these characteristics.
+Fish in the different pelagic and deep-water benthic zones are physically structured, and behave in ways, that differ markedly from each other. Groups of coexisting species within each zone all seem to operate in similar ways, such as the small mesopelagic vertically migrating plankton-feeders, the bathypelagic anglerfishes, and the deep-water benthic rattails.
+Ray finned species, with spiny fins, are rare among deep-sea fishes, which suggests that deep-sea fish are ancient and so well adapted to their environment that invasions by more modern fishes have been unsuccessful. The few ray fins that do exist are mainly in the Beryciformes and Lampriformes, which are also ancient forms. Most deep-sea pelagic fishes belong to their own orders, suggesting a long evolution in deep-sea environments. In contrast, deep-water benthic species, are in orders that include many related shallow-water fishes.
+
+== Mesopelagic fish ==

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+
+Below the epipelagic zone, conditions change rapidly. Between 200 m and about 1000 m, light continues to fade until there is almost none. Temperatures fall through a thermocline to temperatures between 3.9 and 7.8 °C (39.0 and 46.0 °F). This is the twilight or mesopelagic zone. Pressure continues to increase, at the rate of one atm (0.1 MPa) every 10 m (33 ft), while nutrient concentrations fall, along with dissolved oxygen and the rate at which the water circulates.
+Sonar operators, using the newly developed sonar technology during World War II, were puzzled by what appeared to be a false sea floor 300–500 metres (984–1,640 ft) deep by day, and less deep at night. This turned out to be due to millions of marine organisms, most particularly small mesopelagic fish, with swim bladders that reflected the sonar. These organisms migrate up into shallower water at dusk to feed on plankton. The layer is deeper when the moon is out, and can become shallower when clouds pass over the moon. This phenomenon has come to be known as the deep scattering layer.
+Most mesopelagic fish make daily vertical migrations, moving at night into the epipelagic zone, often following similar migrations of zooplankton, and returning to the depths for safety during the day. These vertical migrations often occur over large vertical distances, and are undertaken with the assistance of a swim bladder. The swim bladder is inflated when the fish wants to move up, and, given the high pressures in the messoplegic zone, this requires significant energy. As the fish ascends, the pressure in the swim bladder must adjust to prevent it from bursting. When the fish wants to return to the depths, the swim bladder is deflated. Some mesopelagic fishes make daily migrations through the thermocline, where the temperature changes between 50 and 69 °F (10 and 21 °C), thus displaying considerable tolerances for temperature change.
+These fish have muscular bodies, ossified bones, scales, well developed gills and central nervous systems, and large hearts and kidneys. Mesopelagic plankton feeders have small mouths with fine gill rakers, while the piscivores have larger mouths and coarser gill rakers.
+Mesopelagic fish are adapted for an active life under low light conditions. Most of them are visual predators with large eyes. Some of the deeper water fish have tubular eyes with big lenses and only rod cells that look upwards. These give binocular vision and great sensitivity to small light signals. This adaptation gives improved terminal vision at the expense of lateral vision, and allows the predator to pick out squid, cuttlefish, and smaller fish that are silhouetted against the gloom above them.
+Mesopelagic fish usually lack defensive spines, and use colour to camouflage themselves from other fish. Ambush predators are dark, black or red. Since the longer, red, wavelengths of light do not reach the deep sea, red effectively functions the same as black. Migratory forms use countershaded silvery colours. On their bellies, they often display photophores producing low grade light. For a predator from below, looking upwards, this bioluminescence camouflages the silhouette of the fish. However, some of these predators have yellow lenses that filter the (red deficient) ambient light, leaving the bioluminescence visible.
+The brownsnout spookfish, a species of barreleye, is the only vertebrate known to employ a mirror, as opposed to a lens, to focus an image in its eyes.
+Sampling by deep trawling indicates that lanternfish account for as much as 65% of all deep-sea fish biomass. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. The estimated global biomass of lanternfish is 550–660 million tonnes, several times the entire world fisheries catch. Lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans.
+Bigeye tuna are an epipelagic/mesopelagic species that eats other fish. Satellite tagging has shown that bigeye tuna often spend prolonged periods cruising deep below the surface during the daytime, sometimes making dives as deep as 500 metres (1,640 ft). These movements are thought to be in response to the vertical migrations of prey organisms in the deep scattering layer.
+
+== Bathypelagic fish ==

data/en.wikipedia.org/wiki/Deep-sea_fish-4.md

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+---
+title: "Deep-sea fish"
+chunk: 5/6
+source: "https://en.wikipedia.org/wiki/Deep-sea_fish"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:47.616452+00:00"
+instance: "kb-cron"
+---
+
+Below the mesopelagic zone it is pitch dark. This is the midnight (or bathypelagic zone), extending from 1,000 metres (3,281 ft) to the bottom deep-water benthic zone. If the water is exceptionally deep, the pelagic zone below 4,000 metres (13,123 ft) is sometimes called the lower midnight (or abyssopelagic zone). Temperatures in this zone range from 1 to 4 °C (34 to 39 °F) and it is completely aphotic.
+Conditions are somewhat uniform throughout these zones; the darkness is complete, the pressure is crushing, and temperatures, nutrients and dissolved oxygen levels are all low.
+Bathypelagic fish have special adaptations to cope with these conditions – they have slow metabolisms and unspecialized diets, being willing to eat anything that comes along. They prefer to sit and wait for food rather than waste energy searching for it. The behaviour of bathypelagic fish can be contrasted with the behaviour of mesopelagic fish. Mesopelagic fish are often highly mobile, whereas bathypelagic fish are almost all lie-in-wait predators, normally expending little energy in movement.
+The dominant bathypelagic fishes are small bristlemouth and anglerfish; fangtooth, viperfish, daggertooth and barracudina are also common. These fishes are small, many about 10 centimetres (3.9 in) long, and not many longer than 25 centimetres (9.8 in). They spend most of their time waiting patiently in the water column for prey to appear or to be lured by their phosphors. What little energy is available in the bathypelagic zone filters from above in the form of detritus, faecal material, and the occasional invertebrate or mesopelagic fish. About 20 percent of the food that has its origins in the epipelagic zone falls down to the mesopelagic zone, but only about 5 percent filters down to the bathypelagic zone.
+Bathypelagic fish are sedentary, adapted to outputting minimum energy in a habitat with very little food or available energy, not even sunlight, only bioluminescence. Their bodies are elongated with weak, watery muscles and skeletal structures. Since so much of the fish is water, they are not compressed by the great pressures at these depths. They often have extensible, hinged jaws with recurved teeth. They are slimy, without scales. The central nervous system is confined to the lateral line and olfactory systems, the eyes are small and may not function, and gills, kidneys and hearts, and swim bladders are small or missing. These are the same features found in fish larvae, which suggests that during their evolution, bathypelagic fish have acquired these features through neoteny. As with larvae, these features allow the fish to remain suspended in the water with little expenditure of energy.
+Despite their ferocious appearance, these forms are mostly miniature fish with weak muscles, and are too small to represent any threat to humans. An exception to the generally small size of bathypelagic fish is the Yokozuna slickhead (Narcetes shonanmaruae), described in 2021, which is the largest known entirely bathypelagic bony fish at over 2.5 metres (8.2 ft) in length.
+The swim bladders of deep-sea fish are either absent or scarcely operational, and bathypelagic fish do not normally undertake vertical migrations. Filling bladders at such great pressures incurs huge energy costs. Some deep-sea fishes have swim bladders which function while they are young and inhabit the upper epipelagic zone, but they wither or fill with fat when the fish move down to their adult habitat.
+A couple of known exceptions are the cusk-eel (Holcomycteronus profundissimus), retrieved from 7160 meters deep, and the rough abyssal grenadier (Coryphaenoides yaquinae), found at 7259 meters depth. These species still have functional swim bladders, which allows them to maintain high bone density and strong jaws.
+The most important sensory systems are usually the inner ear, which responds to sound, and the lateral line, which responds to changes in water pressure. The olfactory system can also be important for males who find females by smell.
+Bathypelagic fish are black, or sometimes red, with few photophores. When photophores are used, it is usually to entice prey or attract a mate. Because food is so scarce, bathypelagic predators are not selective in their feeding habits, but grab whatever comes close enough. They accomplish this by having a large mouth with sharp teeth for grabbing large prey and overlapping gill rakers which prevent small prey that have been swallowed from escaping.
+It is not easy finding a mate in this zone. Some species depend on bioluminescence, where bioluminescent patterns are unique to specific species. Others are hermaphrodites, which doubles their chances of producing both eggs and sperm when an encounter occurs. The female anglerfish releases pheromones to attract tiny males. When a male finds her, he bites on to her and never lets go. When a male of the anglerfish species Haplophryne mollis bites into the skin of a female, he releases an enzyme that digests the skin of his mouth and her body, fusing the pair to the point where the two circulatory systems join up. The male then atrophies into nothing more than a pair of gonads. This extreme sexual dimorphism ensures that, when the female is ready to spawn, she has a mate immediately available.
+Many forms other than fish live in the bathypelagic zone, such as squid, large whales, octopuses, sponges, brachiopods, sea stars, and echinoids, but this zone is difficult for fish to live in.

data/en.wikipedia.org/wiki/Deep-sea_fish-5.md

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+---
+title: "Deep-sea fish"
+chunk: 6/6
+source: "https://en.wikipedia.org/wiki/Deep-sea_fish"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:47.616452+00:00"
+instance: "kb-cron"
+---
+
+== Adaptation to high pressure ==
+As a fish moves deeper into the sea, the weight of the water overhead exerts increasing hydrostatic pressure on the fish. This increased pressure amounts to about one atm (0.1 MPa) for every 10 m (33 ft)in depth. For a fish at the bottom of the bathypelagic zone, this pressure amounts to about 400 atm (40 MPa, 6000 psi).
+Deep-sea organisms possess adaptations at cellular and physiological levels that allow them to survive in environments of great pressure. Not having these adaptations limits the depths at which shallow-water species can operate. High levels of external pressure affects how metabolic processes and biochemical reactions proceed. The equilibrium of many chemical reactions is disturbed by pressure, and pressure can inhibit processes which result in an increase in volume. Water, a key component in many biological processes, is very susceptible to volume changes, mainly because constituents of cellular fluid have an effect on water structure. Thus, enzymatic reactions that induce changes in water organization effectively change the system's volume. Proteins responsible for catalyzing reactions are typically held together by weak bonds and the reactions usually involve volume increases.
+Species that can tolerate these depths have evolved changes in their protein structure and reaction criteria to withstand pressure, in order to perform reactions in these conditions. In high pressure environments, bilayer cellular membranes experience a loss of fluidity. Deep-sea cellular membranes favor phospholipid bilayers with a higher proportion of unsaturated fatty acids, which induce a higher fluidity than their sea-level counterparts.
+Ten orders, thirteen families and about 200 known species of deep-sea fish have evolved a gelatinous layer below the skin or around the spine, which is used for buoyancy, low-cost growth and to increase swimming efficiency by reducing drag.
+
+Deep-sea species exhibit lower changes of entropy and enthalpy compared to surface level organisms, since a high pressure and low temperature environment favors negative enthalpy changes and reduced dependence on entropy-driven reactions. From a structural standpoint, globular proteins of deep-sea fish due to the tertiary structure of G-actin are relatively rigid compared to those of surface level fish. The fact that proteins in deep-sea fish are structurally different from surface fish is apparent from the observation that actin from the muscle fibers of deep-sea fish are extremely heat-resistant; an observation similar to what is found in lizards. These proteins are structurally strengthened by modification of the bonds in the tertiary structure of the protein which also happens to induce high levels of thermal stability. Proteins are structurally strengthened to resist pressure by modification of bonds in the tertiary structure. Therefore, high levels of hydrostatic pressure, similar to high body temperatures of thermophilic desert reptiles, favor rigid protein structures.
+
+Na+/K+ -ATPase is a lipoprotein enzyme that plays a prominent role in osmoregulation and is heavily influenced by hydrostatic pressure. The inhibition of Na+/K+ -ATPase is due to increased compression due to pressure. The rate-limiting step of the Na+/K+ -ATPase reaction induces an expansion in the bilayer surrounding the protein, and therefore an increase in volume. An increase in volume makes Na+/K+ -ATPase reactivity susceptible to higher pressures. Even though the Na+/K+ -ATPase activity per gram of gill tissue is lower for deep-sea fishes, the Na+/K+ -ATPases of deep-sea fishes exhibit a much higher tolerance of hydrostatic pressure compared to their shallow-water counterparts. This is exemplified between the species C. acrolepis (around 2000 m deep) and its hadalpelagic counterpart C. armatus (around 4,000 metres (13,123 ft) deep), where the Na+/K+ -ATPases of C. armatus are much less sensitive to pressure. This resistance to pressure can be explained by adaptations in the protein and lipid moieties of Na+/K+ -ATPase. 
+
+== Lanternfish ==
+
+Sampling via deep trawling indicates that lanternfish account for as much as 65% of all deep-sea fish biomass. Indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. With an estimated global biomass of 550–660 million metric tons, several times the entire world fisheries catch, lanternfish also account for much of the biomass responsible for the deep scattering layer of the world's oceans. In the Southern Ocean, Myctophids provide an alternative food resource to krill for predators such as squid and the king penguin. Although these fish are plentiful and prolific, currently only a few commercial lanternfish fisheries exist: these include limited operations off South Africa, in the sub-Antarctic, and in the Gulf of Oman.
+
+== Endangered species ==
+A 2006 study by Canadian scientists has found five species of deep-sea fish – blue hake, spiny eel – to be on the verge of extinction due to the shift of commercial fishing from continental shelves to the slopes of the continental shelves, down to depths of 1,600 metres (5,249 ft). The slow reproduction of these fish – they reach sexual maturity at about the same age as human beings – is one of the main reasons that they cannot recover from the excessive fishing.
+
+== See also ==
+
+Census of Marine Life
+Deep ocean water
+Deep sea
+Deep-sea community
+Demersal fish
+Pelagic fish
+
+== Citations ==
+
+== References ==
+
+== Further reading ==
+Gordon J. D. M. (2001) "Deep-sea fishes" In: John H. Steele, Steve A. Thorpe, Karl K. Turekian (eds.) Elements of Physical Oceanography, pages 227–233, Academic Press. ISBN 9780123757241.
+Hoar W. S., Randall D. J. and Farrell A. P. (eds.) (1997) Deep-Sea Fishes, Academic Press. ISBN 9780080585406.
+Shotton, Ross (1995) "Deepwater fisheries" In: Review of the state of world marine fishery resources, FAO Fisheries technical paper 457, FAO, Rome. ISBN 92-5-105267-0.
+Tandstad M., Shotton R., Sanders J. and Carocci F. (2011) "Deep-sea Fisheries" Archived 3 March 2016 at the Wayback Machine In: Review of the state of world marine fishery resources, pages 265–278, FAO Fisheries technical paper 569, FAO, Rome. ISBN 978-92-5-107023-9.
+
+== External links ==
+
+Deep-Sea Bestiary
+Photo Gallery: Deep-Sea Creatures
+Crash Course To Deep Sea Fishing – articles, facts and images of deep-sea animals

data/en.wikipedia.org/wiki/Deep-sea_wood-0.md

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+---
+title: "Deep-sea wood"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Deep-sea_wood"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:50.198701+00:00"
+instance: "kb-cron"
+---
+
+Deep-sea wood is the term for wood which sinks to the ocean floor. These wood-falls develop deep sea ecosystems.  Deep-sea wood supports  unique forms of deep sea community life including chemo-synthetic bacteria. Sources of carbon for these deep sea ecosystems are not limited to sunken wood, but also include kelp and the remains of whales. Much of what is known about deep-sea wood is obtained from experiments by marine biologists, in which wood is forced to the bottom of the ocean for a set amount of time and is then collected later for sampling.
+
+
+== Organisms present ==
+
+
+=== Wood boring bivalves ===
+Colonization experiments revealed the presence of wood boring bivalves that belong to the subfamily Xylophagainae, such as Xylophaga dorsalis, or other species recently described from deep-sea canyons. They range in shell size from 1 to 10 mm (0.04 to 0.4 in). These bivalves are able to digest wood with the help of symbiotic bacteria in their gills.
+
+
+=== Chemosyntheic fauna ===
+Chemosyntheic mussels identified as Idas modiolaeformis were also found in deep sea wood when organic matter settled for at least one year. They are slightly smaller than the bivalves found and range in length from 1 to 6 mm (0.04 to 0.2 in).
+
+
+=== Other organisms ===
+A variety of deep-sea crabs and sea urchins seemed to also be chemically attracted to the wood. There are numerous species of snail that have been discovered on the wood, along with predatory worms and small crustaceans. Their attraction to the wood may be attributed to its bacterial inhabitants serving as a base organism for deep-sea life, with the potential to feed on microorganisms, or other inhabitants of the wood.
+
+
+== Fungal communities ==
+Fungi are the major degraders of lignocellulose in aquatic environments. In aerobic terrestrial environments, a majority of cellulose breakdown is broken down by wood-decay fungi commonly and collectively known as white rot and soft rot. Complex enzymes are secreted by the various fungi, converting cellulose into a carbon form that can be used by the fungus, and subsequently any organism up the food chain.
+
+
+== Bacterial communities ==
+Bacteria also contribute to the digestion of deep-sea wood, using an alternative method from that of fungi. In order to classify bacteria present on deep-sea wood, a variety of different techniques are employed. First, biomass allows scientists to quantify the amount of bacterial growth on a sample. Then DNA extraction and Automated Ribosomal Intergenic Spacer analysis (ARISA) can be used to identify the strains of bacteria present that are most dominant, and the ones that are present.
+While Gammaproteobacteria dominated the composition of bacteria found on freshly submerged wood, many other bacterial strains populated in response to colonization of the aforementioned wood-boring Xylophaga, which take the large chunks of wood and convert them into fine chips and fecal matter. These processed forms of carbon lead to the growth of many other marine bacteria including Alphaproteobacteria, Flavobacteria, Actinobacteria, Clostridia, and Bacteroidetes.
+
+
+=== Wood degradation ===
+
+
+==== Presence of anaerobes ====
+The presence of Clostridia, obligate anaerobes suggests that the process of degrading the deep-sea wood may create oxygen-free environments for these bacteria to survive in.
+
+
+==== Sulfur reducing bacteria ====
+Many bacterial strains that were found on deep-sea wood were sulfur-reducing bacteria, meaning they obtain energy from reducing elemental sulfur, instead of traditionally using the sun for energy like almost all other organisms. Marine biologists suggest they may contribute to the breakdown of cellulose from the wood.
+
+
+== Variability of organisms ==
+The species of wood that falls to the ocean floor produces variability in the organisms present on it. There is also natural viability between organisms found on the same species of tree, which promotes to deep-sea diversity. In fact, a study by marine biologists showed bacterial communities were approximately 75% dissimilar, even as similar logs of the same tree species were placed within the same 500 m2 (0.12-acre) area.
+
+
+== References ==

data/en.wikipedia.org/wiki/Deep_ocean_water-0.md

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+---
+title: "Deep ocean water"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Deep_ocean_water"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:48.870613+00:00"
+instance: "kb-cron"
+---
+
+Deep ocean water (DOW) is the name for cold, salty water found in the deep sea, starting at 200 m (660 ft) below the surface of Earth's oceans.  Ocean water differs in temperature and salinity. Warm surface water is generally saltier than the cooler deep or polar waters; in polar regions, the upper layers of ocean water are cold and fresh.  Deep ocean water makes up about 90% of the volume of the oceans. Deep ocean water has a very uniform temperature, around 0–3 °C (32–37 °F), and a salinity of about 3.5% or, as oceanographers state, 35‰ (parts per thousand).
+In specialized locations, such as the Natural Energy Laboratory of Hawaii, ocean water is pumped to the surface from approximately 900 m (3,000 ft) deep for applications in research, commercial and pre-commercial activities. DOW is typically used to describe ocean water at sub-thermal depths sufficient to provide a measurable difference in water temperature.
+
+
+== Cold-bed agriculture ==
+A potential indirect use of cold ocean water is "cold-bed agriculture".  During condensation or ocean thermal energy conversion operations, the water does not reach ambient temperature, because a certain temperature gradient is required to make these processes viable. The water leaving those operations is therefore still colder than the surroundings, and a further benefit can be extracted by passing this water through underground pipes, thereby cooling agricultural soil. This reduces evaporation, and even causes water to condense from the atmosphere. This allows agricultural production where crops would normally not be able to grow. This technique is sometimes referred to as "cold agriculture" or "cold-bed agriculture".
+
+
+== See also ==
+
+Deep sea fish
+Deep ocean minerals
+
+
+== References ==

data/en.wikipedia.org/wiki/Deep_sea-0.md

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+---
+title: "Deep sea"
+chunk: 1/3
+source: "https://en.wikipedia.org/wiki/Deep_sea"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:46.246452+00:00"
+instance: "kb-cron"
+---
+
+The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 m (660 ft) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure. The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore.
+Organisms living within the deep sea have a variety of adaptations to survive in these conditions. Organisms can survive in the deep sea through a number of feeding methods including scavenging, predation and filtration, with a number of organisms surviving by feeding on marine snow. Marine snow is organic material that has fallen from upper waters into the deep sea.
+In 1960, the bathyscaphe Trieste descended to the bottom of the Mariana Trench near Guam, at 10,911 m (35,797 ft; 6.780 mi), the deepest known spot in any ocean. If Mount Everest (8,848 m or 29,029 ft or 5.498 mi) were submerged there, its peak would be more than 2 km (1.2 mi) beneath the surface. After the Trieste was retired, the Japanese remote-operated vehicle (ROV) Kaikō was the only vessel capable of reaching this depth until it was lost at sea in 2003. In May and June 2009, the hybrid-ROV Nereus returned to the Challenger Deep for a series of three dives to depths exceeding 10,900 m (35,800 ft; 6.8 mi).
+
+== Environmental characteristics ==
+
+=== Light ===
+Natural light does not penetrate the deep ocean, with the exception of the upper parts of the mesopelagic. Since photosynthesis is not possible, plants and phytoplankton cannot live in this zone, and as these are the primary producers of almost all of earth's ecosystems, life in this area of the ocean must depend on energy sources from elsewhere. Except for the areas close to the hydrothermal vents, this energy comes from organic material drifting down from the photic zone. The sinking organic material is composed of algal particulates, detritus, and other forms of biological waste, which is collectively referred to as marine snow.
+
+=== Pressure ===
+Because pressure in the ocean increases by about 1 atmosphere for every 10 meters of depth, the amount of pressure experienced by many marine organisms is extreme. Until recent years, the scientific community lacked detailed information about the effects of pressure on most deep sea organisms because the specimens encountered arrived at the surface dead or dying and weren't observable at the pressures at which they lived. With the advent of traps that incorporate a special pressure-maintaining chamber, undamaged larger metazoan animals have been retrieved from the deep sea in good condition.
+
+=== Salinity ===
+Salinity is remarkably constant throughout the deep sea, at about 35 parts per thousand. There are some minor differences in salinity, but none that are ecologically significant, except in largely landlocked seas like the Mediterranean and Red Seas.
+
+=== Temperature ===
+The two areas of greatest temperature gradient in the oceans are the transition zone between the surface waters and the deep waters, the thermocline, and the transition between the deep-sea floor and the hot water flows at the hydrothermal vents. Thermoclines vary in thickness from a few hundred meters to nearly a thousand meters. Below the thermocline, the water mass of the deep ocean is cold and far more homogeneous. Thermoclines are strongest in the tropics, where the temperature of the epipelagic zone is usually above 20 °C (68 °F). From the base of the epipelagic, the temperature drops over several hundred meters to 5–6 °C at 1,000 meters (41–43 °F at 3,300 ft). It continues to decrease to the bottom, but the rate is much slower. The cold water stems from sinking heavy surface water in the polar regions.
+At any given depth, the temperature is practically unvarying over long periods of time, without seasonal changes and with very little interannual variability. No other habitat on earth has such a constant temperature.
+In hydrothermal vents the temperature of the water as it emerges from the "black smoker" chimneys may be as high as 400 °C (752 °F), being kept from boiling by the high hydrostatic pressure – thus being superheated water. The temperature may back down to 2 to 4 °C (36 to 39 °F) within a few meters.
+
+== Biology ==

data/en.wikipedia.org/wiki/Deep_sea-1.md

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+---
+title: "Deep sea"
+chunk: 2/3
+source: "https://en.wikipedia.org/wiki/Deep_sea"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:46.246452+00:00"
+instance: "kb-cron"
+---
+
+Regions below the epipelagic are divided into further zones, beginning with the bathyal zone (also considered the continental slope) which spans from 200 to 3,000 meters (660 to 9,840 ft) below sea level and is essentially transitional, containing elements from both the shelf above and the abyss below. Below this zone, the deep sea consists of the abyssal zone (ocean depth between 3–6 km; 1.9–3.7 mi) and the hadal zone (6–11 km; 3.7–6.8 mi). Food consists of falling organic matter known as 'marine snow' and carcasses derived from the productive zone above, and is scarce both in terms of spatial and temporal distribution.
+Instead of relying on gas for their buoyancy, many deep-sea species have jelly-like flesh consisting mostly of glycosaminoglycans, which provides them with very low density. It is also common among deep water squid to combine the gelatinous tissue with a flotation chamber filled with a coelomic fluid made up of the metabolic waste product ammonium chloride, which is lighter than the surrounding water.
+The midwater fish have special adaptations to cope with these conditions—they are small, usually being under 25 centimetres (10 in); they have slow metabolisms and unspecialized diets, preferring to sit and wait for food rather than waste energy searching for it. They have elongated bodies with weak, watery muscles and skeletal structures. They often have extendable, hinged jaws with recurved teeth. Because of the sparse distribution and lack of light, finding a partner with which to breed is difficult, and many organisms are hermaphroditic.
+Because light is so scarce, fish often have larger than normal, tubular eyes with only rod cells. Their upward field of vision allows them to seek out the silhouette of possible prey. Prey fish however also have adaptations to cope with predation. These adaptations are mainly concerned with reduction of silhouettes, a form of camouflage. The two main methods by which this is achieved are reduction in the area of their shadow by lateral compression of the body, and counter illumination via bioluminescence. This is achieved by production of light from ventral photophores, which tend to produce such light intensity to render the underside of the fish of similar appearance to the background light. For more sensitive vision in low light, some fish have a retroreflector behind the retina.  Flashlight fish have this plus photophores, which combination they use to detect eyeshine in other fish (see tapetum lucidum).
+Organisms in the deep sea are almost entirely reliant upon sinking living and dead organic matter which falls at approximately 100 meters per day. In addition, only about 1 to 3% of the production from the surface reaches the seabed, mostly in the form of marine snow. This ends up accumulating on the benthic floor, around 1 cm every 1,000 years. Larger food falls, such as whale carcasses, also occur and studies have shown that these may happen more often than currently believed. There are many scavengers that feed primarily or entirely upon large food falls and the distance between whale carcasses is estimated to only be 8 kilometers. In addition, there are a number of filter feeders that feed upon organic particles using tentacles, such as Freyella elegans.
+Marine bacteriophages play an important role in cycling nutrients in deep sea sediments. They are extremely abundant (between 5×1012 and 1×1013 phages per square meter) in sediments around the world.
+Despite being so isolated, deep sea organisms have still been harmed by human interaction with the oceans. The London Convention aims to protect the marine environment from dumping of wastes such as sewage sludge and radioactive waste. A study found that at one region there had been a decrease in deep sea coral from 2007 to 2011, with the decrease being attributed to global warming and ocean acidification, and biodiversity estimated as being at the lowest levels in 58 years. Ocean acidification is particularly harmful to deep sea corals because they are made of aragonite, an easily soluble carbonate, and because they are particularly slow growing and will take years to recover. Deep sea trawling is also harming the biodiversity by destroying deep sea habitats which can take years to form. Another human activity that has altered deep sea biology is mining. One study found that at one mining site fish populations had decreased at six months and at three years, and that after twenty six years populations had returned to the same levels as prior to the disturbance.
+
+=== Chemosynthesis ===
+There are a number of species that do not primarily rely upon dissolved organic matter for their food. These species and communities are found at hydrothermal vents at sea-floor spreading zones. One example is the symbiotic relationship between the tube worm Riftia and chemosynthetic bacteria. It is this chemosynthesis that supports the complex communities that can be found around hydrothermal vents. These complex communities are one of the few ecosystems on the planet that do not rely upon sunlight for their supply of energy.

data/en.wikipedia.org/wiki/Deep_sea-2.md

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+---
+title: "Deep sea"
+chunk: 3/3
+source: "https://en.wikipedia.org/wiki/Deep_sea"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:46.246452+00:00"
+instance: "kb-cron"
+---
+
+=== Adaptation to hydrostatic pressure ===
+Deep-sea fish have different adaptations in their proteins, anatomical structures, and metabolic systems to survive in the Deep sea, where the inhabitants have to withstand great amount of hydrostatic pressure. While other factors like food availability and predator avoidance are important, the deep-sea organisms must have the ability to maintain well-regulated metabolic system in the face of high pressures. In order to adjust for the extreme environment, these organisms have developed unique characteristics.
+Proteins are affected greatly by the elevated hydrostatic pressure, as they undergo changes in water organization during hydration and dehydration reactions of the binding events. This is due to the fact that most enzyme-ligand interactions form through charged or polar non-charge interactions. Because hydrostatic pressure affects both protein folding and assembly and enzymatic activity, the deep sea species must undergo physiological and structural adaptations to preserve protein functionality against pressure.
+Actin is a protein that is essential for different cellular functions. The α-actin serves as a main component for muscle fiber, and it is highly conserved across numerous different species. Some Deep-sea fish developed pressure tolerance through the change in mechanism of their α-actin. In some species that live in depths greater than 5 km (3.1 mi), C.armatus and C.yaquinae have specific substitutions on the active sites of α-Actin, which serves as the main component of muscle fiber. These specific substitutions, Q137K and V54A from C.armatus or I67P from  C.yaquinae are predicted to have importance in pressure tolerance. Substitution in the active sites of actin result in significant changes in the salt bridge patterns of the protein, which allows for better stabilization in ATP binding and sub unit arrangement, confirmed by the free energy analysis and molecular dynamics simulation. It was found that deep sea fish have more salt bridges in their actins compared to fish inhabiting the upper zones of the sea.
+In relations to protein substitution, specific osmolytes were found to be abundant in deep sea fish under high hydrostatic pressure. For certain chondrichthyans, it was found that Trimethylamine N-oxide (TMAO) increased with depth, replacing other osmolytes and urea. Due to the ability of TMAO being able to protect proteins from high hydrostatic pressure destabilizing proteins, the osmolyte adjustment serves are an important adaptation for deep sea fish to withstand high hydrostatic pressure.
+Deep-sea organisms possess molecular adaptations to survive and thrive in the deep oceans. Mariana hadal snailfish developed modification in the Osteocalcin(burlap) gene, where premature termination of the gene was found. Osteocalcin gene regulates bone development and tissue mineralization, and the frameshift mutation seems to have resulted in the open skull and cartilage-based bone formation. Due to high hydrostatic pressure in the deep sea, closed skulls that organisms living on the surface develop cannot withstand the enforcing stress. Similarly, common bone developments seen in surface vertebrates cannot maintain their structural integrity under constant high pressure.
+
+== Exploration ==
+
+It has been suggested that more is known about the Moon than the deepest parts of the ocean. This is a common misconception based on a 1953 statement by George E.R. Deacon published in the Journal of Navigation, and largely refers to the scarce amount of seafloor bathymetry available at the time. The similar idea that more people have stood on the moon than have been to the deepest part of the ocean is likewise dubious.
+Still, the deep-sea remains one of the least explored regions on planet Earth. Pressures even in the mesopelagic become too great for traditional exploration methods, demanding alternative approaches for deep-sea research. Baited camera stations, small crewed submersibles, and ROVs (remotely operated vehicles) are three methods utilized to explore the ocean's depths. Because of the difficulty and cost of exploring this zone, current knowledge is limited. Pressure increases at approximately one atmosphere for every 10 meters meaning that some areas of the deep sea can reach pressures of above 1,000 atmospheres. This not only makes great depths very difficult to reach without mechanical aids, but also provides a significant difficulty when attempting to study any organisms that may live in these areas as their cell chemistry will be adapted to such vast pressures.
+
+== See also ==
+Deep ocean water – Cold, salty water deep below the surface of Earth's oceans
+Submarine landslide – Landslides that transport sediment across the continental shelf and into the deep ocean
+The Blue Planet – 2001 British nature documentary television series
+Blue Planet II – 2017 British nature documentary television series
+Nepheloid layer – Layer of water in deep sea
+Biogenous ooze
+ Oceans portal
+
+== References ==
+
+== External links ==
+
+Deep Sea Foraminifera – Deep Sea Foraminifera from 4400 meters depth, Antarctica – an image gallery and description of hundreds of specimens
+Deep Ocean Exploration on the Smithsonian Ocean Portal
+Deep-Sea Creatures Facts and images from the deepest parts of the ocean
+How Deep Is The Ocean Archived 2016-06-15 at the Wayback Machine Facts and infographic on ocean depth

data/en.wikipedia.org/wiki/Demersal_zone-0.md

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+---
+title: "Demersal zone"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Demersal_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:51.436336+00:00"
+instance: "kb-cron"
+---
+
+The demersal zone (from Latin demergere, "to sink") is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone.
+Being just above the ocean floor, the demersal zone is variable in depth and can be part of the photic zone where light can penetrate, and photosynthetic organisms grow, or the aphotic zone, which begins between depths of roughly 200 and 1,000 m (700 and 3,300 ft) and extends to the ocean depths, where no light penetrates.
+
+
+== Fish ==
+
+The distinction between demersal species of fish and pelagic species is not always clear cut. The Atlantic cod (Gadus morhua) is a typical demersal fish, but can also be found in the open water column, and the Atlantic herring (Clupea harengus) is predominantly a pelagic species but forms large aggregations near the seabed when it spawns on banks of gravel.
+Two types of fish inhabit the demersal zone: those that are heavier than water and rest on the seabed, and those that have neutral buoyancy and remain just above the substrate. In many species of fish, neutral buoyancy is maintained by a gas-filled swim bladder which can be expanded or contracted as the circumstances require. A disadvantage of this method is that adjustments need to be made constantly as the water pressure varies when the fish swims higher and lower in the water column. An alternative buoyancy aid is the use of lipids, which are less dense than water—squalene, commonly found in shark livers, has a specific gravity of just 0.86. In the velvet belly lanternshark (Etmopterus spinax), a benthopelagic species, 17% of the bodyweight is liver of which 70% are lipids. Benthic rays and skates have smaller livers with lower concentrations of lipids; they are therefore denser than water and they do not swim continuously, intermittently resting on the seabed. Some fish have no buoyancy aids but use their pectoral fins which are so angled as to give lift as they swim. The disadvantage of this is that, if they stop swimming, the fish sink, and they cannot hover, or swim backwards.
+Demersal fish have various feeding strategies; many feed on zooplankton or organisms or algae on the seabed; some of these feed on epifauna (invertebrates on top of the seafloor), while others specialise on infauna (invertebrates that burrow beneath the seafloor). Others are scavengers, eating the dead remains of plants or animals, while still others are predators.
+
+
+== Invertebrates ==
+Zooplankton are animals that drift with the current, but many have some limited means of locomotion and have some control over the depths at which they drift. They use gas-filled sacs or accumulations of substances with low densities to provide buoyancy, or they may have structures that slow down any passive descent. Where the adult, benthic organism is limited to life in a certain range of depths, their larvae need to optimise their chances of settling on a suitable substrate.
+Cuttlefish are able to adjust their buoyancy using their cuttlebones, lightweight rigid structures with cavities filled with gas, which have a specific gravity of about 0.6. This enables them to swim at varying depths. Another invertebrate that feeds on the seabed and has swimming abilities is the nautilus, which stores gas in its chambers and adjusts its buoyancy by use of osmosis, pumping water in and out.
+
+
+== References ==

data/en.wikipedia.org/wiki/Fracture_zone-0.md

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+---
+title: "Fracture zone"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Fracture_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:52.674187+00:00"
+instance: "kb-cron"
+---
+
+A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics.  Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs.  Fracture zones extend past the transform faults, away from the ridge axis; are usually seismically inactive (because both plate segments are moving in the same direction), although they can display evidence of transform fault activity, primarily in the different ages of the crust on opposite sides of the zone.
+In actual usage, many transform faults aligned with fracture zones are often loosely referred to as "fracture zones" although technically, they are not. They can be associated with other tectonic features and may be subducted or distorted by later tectonic activity. They are usually defined with bathymetric, gravity and magnetic studies.
+
+
+== Structure and formation ==
+Mid-ocean ridges are divergent plate boundaries. As the plates on either side of an offset mid-ocean ridge move, a transform fault forms at the offset between the two ridges.
+Fracture zones and the transform faults that form them are separate but related features. Transform faults are plate boundaries, meaning that on either side of the fault is a different plate. In contrast, outside of the ridge-ridge transform fault, the crust on both sides belongs to the same plate, and there is no relative motion along the junction. The fracture zone is thus the junction between oceanic crustal regions of different ages.  Because younger crust is generally higher due to increased thermal buoyancy, the fracture zone is characterized by an offset in elevation with an intervening canyon that may be topographically distinct for hundreds or thousands of kilometers on the sea floor.
+
+
+== Geologic importance ==
+
+As many areas of the ocean floor, particularly the Atlantic Ocean, are currently inactive, it can be difficult to find past plate motion. However, by observing the fracture zones, one can determine both the direction and rate of past plate motion. This is found by observing the patterns of magnetic striping on the ocean floor (a result of the reversals of Earth's magnetic field over time). By measuring the offset in the magnetic striping, one can then determine the rate of past plate motions. In a similar method, one can use the relative ages of the seafloor on either side of a fracture zone to determine the rate of past plate motions. By comparing how offset similarly aged seafloor is, one can determine how quickly the plate has moved.
+
+
+== Examples ==
+
+
+=== Blanco fracture zone ===
+The Blanco fracture zone is a fracture zone running between the Juan de Fuca Ridge and the Gorda Ridge. The dominating feature of the fracture zone is the 150 km (93 mi) long Blanco Ridge, which is a high-angle, right-lateral strike slip fault with some component of dip-slip faulting.
+
+
+=== Charlie-Gibbs fracture zone ===
+The Charlie-Gibbs fracture zone consists of two fracture zones in the North Atlantic that extend for over 2,000 km (1,200 mi). These fracture zones displace the Mid-Atlantic Ridge a total of 350 km (220 mi) to the west. The section of the Mid-Atlantic Ridge between the two fracture zones is seismically active. The flow of major North Atlantic currents is associated with this fracture zone which hosts a diverse deep water ecosystem.
+
+
+=== Heirtzler fracture zone ===
+The Heirtzler fracture zone was named after James Ransom Heirtzler, who first demonstrated through magnetostratigraphy that the Mid-Atlantic Ridge was spreading south of Iceland, providing the first clear evidence for plate tectonics. This name was approved by the Advisory Committee on Undersea Features in 1993. The area around the Heirtzler fracture zone and the Pacific–Antarctic Ridge which is a southwestern portion of the East Pacific Rise has been mapped in detail by amongst other techniques magnetostratigraphy (see picture on this page).
+
+
+=== Mendocino fracture zone ===
+The Mendocino fracture zone extends for over 4,000 km (2,500 mi) off the coast of California and separates the Pacific plate and Gorda plate. The bathymetric depths on the north side of the fracture zone are 800 to 1,200 m (2,600 to 3,900 ft) shallower than to the south, suggesting the seafloor north of the ridge to be younger. Geologic evidence backs this up, as rocks were found to be 23 to 27 million years younger north of the ridge than to the south.
+
+
+=== Romanche fracture zone ===
+Also known as the Romanche Trench, this fracture zone separates the North Atlantic and South Atlantic oceans. The trench reaches 7,758 m (25,453 ft) deep, is 300 km (190 mi) long, and has a width of 19 km (12 mi). The fracture zone offsets the Mid-Atlantic Ridge by more than 640 km (400 mi).
+
+
+=== Sovanco fracture zone ===
+The Sovanco fracture zone is a dextral-slip transform fault running between the Juan de Fuca and Explorer Ridge in the North Pacific Ocean. The fracture zone is 125 km (78 mi) long and 15 km (9.3 mi) wide.
+
+
+== See also ==
+Plate reconstruction
+ Oceans portal
+
+
+== References ==

data/en.wikipedia.org/wiki/Gas_hydrate_stability_zone-0.md

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+---
+title: "Gas hydrate stability zone"
+chunk: 1/1
+source: "https://en.wikipedia.org/wiki/Gas_hydrate_stability_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:53.961204+00:00"
+instance: "kb-cron"
+---
+
+Gas hydrate stability zone, abbreviated GHSZ, also referred to as methane hydrate stability zone (MHSZ) or hydrate stability zone (HSZ), refers to a zone and depth of the marine environment at which methane clathrates naturally exist in the Earth's crust.
+
+
+== Description ==
+Gas hydrate stability primarily depends upon temperature and pressure, however other variables such as gas composition and ionic impurities in water influence stability boundaries. The existence and depth of a hydrate deposit is often indicated by the presence of a bottom-simulating reflector (BSR). A BSR is a seismic reflection indicating the lower limit of hydrate stability in sediments due to the different densities of hydrate saturated sediments, normal sediments and those containing free gas.
+
+
+== Limits ==
+The upper and lower limits of the HSZ, as well as its thickness, depend upon the local conditions in which the hydrate occurs. The conditions for hydrate stability generally restrict natural deposits to polar regions and deep oceanic regions. In polar regions, due to low temperatures, the upper limit of the hydrate stability zone occurs at a depth of approximately 150 meters.1 The maximal depth of the hydrate stability zone is limited by the geothermal gradient. Along continental margins the average thickness of the HSZ is about 500 m. The upper limit in oceanic sediments occurs when bottom water temperatures are at or near 0 °C, and at a water depth of approximately 300 meters.1 The lower limit of the HSZ is bounded by the geothermal gradient. As depth below seafloor increases, the temperature eventually becomes too high for hydrates to exist. In areas of high geothermal heat flow, the lower limit of the HSZ may become shallower, therefore decreasing the thickness of the HSZ. Conversely, the thickest hydrate layers and widest HSZ are observed in areas of low geothermal heat flow. Generally, the maximum depth of HSZ extension is 2000 meters below the Earth's surface.1,3 Using the location of a BSR, as well as the pressure-temperature regimen necessary for hydrate stability, the HSZ may be used to determine geothermal gradients.2
+
+
+== Transport ==
+If processes such as sedimentation or subduction transport hydrates below the lower limit of the HSZ, the hydrate becomes unstable and disassociates, releasing gas. This free gas may become trapped beneath the overlying hydrate layer, forming gas pockets, or reservoirs. The pressure from the presence of gas reservoirs impacts the stability of the hydrate layer. If this pressure is substantially changed, the stability of the methane layer above will be altered and may result in significant destabilization and disassociation of the hydrate deposit. Landslides of rock or sediment above the hydrate stability zone may also impact the hydrate stability. A sudden decrease in pressure can release gasses or destabilize portions of the hydrate deposit. Changing atmospheric and oceanic temperatures may impact the presence and depth of the hydrate stability zone, however, is still uncertain to what extent. In oceanic sediments, increasing pressure due to a rise in sea level may offset some of the impact of increasing temperature upon the hydrate stability equilibrium.1
+
+
+== References ==

data/en.wikipedia.org/wiki/Hadal_zone-0.md

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+---
+title: "Hadal zone"
+chunk: 1/2
+source: "https://en.wikipedia.org/wiki/Hadal_zone"
+category: "reference"
+tags: "science, encyclopedia"
+date_saved: "2026-05-05T07:34:56.432817+00:00"
+instance: "kb-cron"
+---
+
+The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone ranges from around 6 to 11 km (3.7 to 6.8 mi; 20,000 to 36,000 ft) below sea level, and exists in long, narrow, topographic V-shaped depressions.
+The total area occupied by the 46 individual hadal habitats worldwide is less than 0.25% of the world's seafloor, yet trenches account for over 40% of the ocean's depth range. Most hadal habitats are found in the Pacific Ocean, the largest and deepest of the conventional oceanic divisions.
+
+== Terminology and definition ==
+Historically, the hadal zone was not recognized as distinct from the abyssal zone, although the deepest sections were sometimes called "ultra-abyssal". During the early 1950s, the Danish Galathea II and Soviet Vityaz expeditions separately discovered a distinct shift in the life at depths of 6,000–7,000 m (20,000–23,000 ft) not recognized by the broad definition of the abyssal zone. The term "hadal" was first proposed in 1956 by Anton Frederik Bruun to describe the parts of the ocean deeper than 6,000 m (20,000 ft), leaving abyssal for the parts at 4,000–6,000 m (13,000–20,000 ft). The name refers to Hades, the ancient Greek god of the underworld. About 94% of the hadal zone is found in subduction trenches.
+Depths in excess of 6,000 m (20,000 ft) are generally in oceanic trenches, but there are also trenches at shallower depths. These shallower trenches lack the distinct shift in lifeforms and are therefore not hadal. Although the hadal zone has gained widespread recognition and many continue to use the first proposed limit of 6,000 m (20,000 ft), it has been observed that 6,000–7,000 m (20,000–23,000 ft) represents a gradual transition between the abyssal and hadal zones, leading to the suggestion of placing the limit in the middle, at 6,500 m (21,300 ft). Among others, this intermediate limit has been adopted by UNESCO. Similar to other depth ranges, the fauna of the hadal zone can be broadly placed into two groups: hadobenthic species (compare benthic zone) living on or at the seabottom/sides of trenches, and hadopelagic species (compare pelagic zone) living in open water.
+
+== Ecology ==
+
+The deepest ocean trenches are considered the least explored and most extreme marine ecosystems. They are characterized by complete lack of sunlight, low temperatures, nutrient scarcity, and extremely high hydrostatic pressures. The major sources of nutrients and carbon are fallout from upper layers, drifts of fine sediment, and landslides. Most organisms are scavengers and detrivores. As of 2020, over 400 species are known from hadal ecosystems, many of which possess physiological adaptations to the extreme environmental conditions. There are high levels of endemism, and noteworthy examples of gigantism in amphipods, mysids, and isopods and dwarfism in  nematodes, copepods, and kinorhynchs.
+
+Marine life decreases with depth, both in abundance and biomass, but there is a wide range of metazoan organisms in the hadal zone, mostly benthos, including fish, sea cucumber, bristle worms, bivalves, isopods, sea anemones, amphipods, copepods, decapod crustaceans and gastropods. Most of these trench communities probably originated in the abyssal plains. Although they have evolved adaptations to high pressure and low temperatures such as lower metabolism, intra-cellular protein-stabilising osmolytes, and unsaturated fatty acids in cell membrane phospholipids, there is no consistent relationship between pressure and metabolic rate in these communities. Increased pressure can instead constrain the ontogenic or larval stages of organisms. Pressure increases ten-fold as an organism moves from sea level to a depth of 90 m (300 ft), whilst pressure only doubles as an organism moves from 6,000 to 11,000 m (20,000 to 36,000 ft).
+Over a geological time scale, trenches can become accessible as previously stenobathic (limited to a narrow depth range) fauna evolve to become eurybathic (adapted to a wider range of depths), such as grenadiers and natantian prawns. Trench communities do, nevertheless, display a contrasting degree of intra-trench endemism and inter-trench similarities at a higher taxonomic level.
+Only a relatively small number of fish species are known from the hadal zone, including certain grenadiers, cutthroat eels, pearlfish, cusk-eels, snailfish and eelpouts. Due to the extreme pressure, the theoretical maximum depth for vertebral fish may be about 8,000–8,500 m (26,200–27,900 ft), below which teleosts would be hyperosmotic, assuming trimethylamine N-oxide requirements follow the observed approximate linear relationship with depth. Some invertebrates do occur deeper, such as bigfin squid, certain polynoid worms, myriotrochid sea cucumbers, turrid snails and pardaliscid amphipods in excess of 10,000 m (33,000 ft). In addition, giant protists known as Xenophyophora (foraminifera) live at these depths.
+
+== Conditions ==
+The only known primary producers in the hadal zone are certain bacteria that are able to metabolize hydrogen and methane released by rock and seawater reactions (serpentinization), or hydrogen sulfide released from cold seeps. Some of these bacteria are symbiotic, for example living inside the mantle of certain thyasirid and vesicomyid bivalves. Otherwise the first link in the hadal food web are heterotroph organisms that feed on marine snow, both fine particles and the occasional carcass.
+The hadal zone can reach far below 6,000 m (20,000 ft) deep; the deepest known extends to 10,911 m (35,797 ft). At such depths, the pressure in the hadal zone exceeds 1,100 standard atmospheres (110 MPa; 16,000 psi). Lack of light and extreme pressure makes this part of the ocean difficult to explore.