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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Megatsunami | 7/10 | https://en.wikipedia.org/wiki/Megatsunami | reference | science, encyclopedia | 2026-05-05T07:35:36.838495+00:00 | kb-cron |
==== 1963: Vajont Dam, Italy ====
On 9 October 1963, a landslide above Vajont Dam in Italy produced a 250 m (820 ft) surge that overtopped the dam and destroyed the villages of Longarone, Pirago, Rivalta, Villanova, and Faè, killing nearly 2,000 people. This is currently the only known example of a megatsunami that was indirectly caused by human activities.
==== 1964: Valdez Arm, Alaska ==== On 27 March 1964, the 1964 Alaska earthquake triggered a landslide that generated a megatsunami which reached a height of 70 metres (230 ft) in the Valdez Arm of Prince William Sound in Southcentral Alaska.
==== 1980: Spirit Lake, Washington, US ====
On 18 May 1980, the upper 400 metres (1,300 ft) of Mount St. Helens collapsed, creating a landslide. This released the pressure on the magma trapped beneath the summit bulge which exploded as a lateral blast, which then released the pressure on the magma chamber and resulted in a plinian eruption. One lobe of the avalanche surged onto Spirit Lake, causing a megatsunami which pushed the lake waters in a series of surges, which reached a maximum height of 260 metres (850 ft) above the pre-eruption water level (about 975 m (3,199 ft) ASL). Above the upper limit of the tsunami, trees lie where they were knocked down by the pyroclastic surge; below the limit, the fallen trees and the surge deposits were removed by the megatsunami and deposited in Spirit Lake.
==== 2000: Paatuut, Greenland ==== On 21 November 2000, a landslide composed of 90,000,000 cubic metres (120,000,000 cu yd) of rock with a mass of 260,000,000 tons fell from an elevation of 1,000 to 1,400 metres (3,300 to 4,600 ft) at Paatuut on the Nuussuaq Peninsula on the west coast of Greenland, reaching a speed of 140 kilometres per hour (87 mph). About 30,000,000 cubic metres (39,000,000 cu yd) of material with a mass of 87,000,000 tons entered Sullorsuaq Strait (known in Danish as Vaigat Strait), generating a megatsunami. The wave had a run-up height of 50 metres (164 ft) near the landslide and 28 metres (92 ft) at Qullissat, the site of an abandoned settlement across the strait on Disko Island, 20 kilometres (11 nmi; 12 mi) away, where it inundated the coast as far as 100 metres (328 ft) inland. Refracted energy from the tsunami created a wave that destroyed boats at the closest populated village, Saqqaq, on the southwestern coast of the Nuussuaq Peninsula 40 kilometres (25 mi) from the landslide.
==== 2007: Chehalis Lake, British Columbia, Canada ==== On 4 December 2007, a landslide composed of 3,000,000 cubic metres (3,900,000 cu yd) of rock and debris fell from an elevation of 550 metres (1,804 ft) on the slope of Mount Orrock on the western short of Chehalis Lake. The landslide entered the 175-metre (574 ft) deep lake, generating a megatsunami with a run-up height of 37.8 metres (124 ft) on the opposite shore and 6.3 metres (21 ft) at the lake's exit point 7.5 kilometres (4.7 mi) away to the south. The wave then continued down the Chehalis River for about 15 kilometres (9.3 mi).
==== 2015: Taan Fiord, Alaska, US ====
At 8:19 p.m. Alaska Daylight Time on 17 October 2015, the side of a mountain collapsed at the head of Taan Fiord, a finger of Icy Bay in Alaska. Some of the resulting landslide came to rest on the toe of Tyndall Glacier, but about 180,000,000 short tons (161,000,000 long tons; 163,000,000 metric tons) of rock with a volume of about 50,000,000 cubic metres (65,400,000 cu yd) fell into the fjord. The landslide generated a megatsunami with an initial height of about 100 metres (330 feet) that struck the opposite shore of the fjord, with a run-up height there of 193 metres (633 feet). Over the next 12 minutes, the wave traveled down the fjord at a speed of up to 97 kilometres per hour (60 mph), with run-up heights of over 100 metres (328 feet) in the upper fjord to between 30 and 100 metres (98 and 330 feet) or more in its middle section, and 20 metres (66 feet) or more at its mouth. Still probably 12 metres (40 feet) tall when it entered Icy Bay, the tsunami inundated parts of Icy Bay's shoreline with run-ups of 4 to 5 metres (13 to 16 feet) before dissipating into insignificance at distances of 5 kilometres (3.1 mi) from the mouth of Taan Fiord, although the wave was detected 140 kilometres (87 miles) away. Occurring in an uninhabited area, the event was unwitnessed, and several hours passed before the signature of the landslide was noticed on seismographs at Columbia University in New York City.
==== 2017: Karrat Fjord, Greenland ==== On 17 June 2017, 35,000,000 to 58,000,000 cubic metres (46,000,000 to 76,000,000 cu yd) of rock on the mountain Ummiammakku fell from an elevation of roughly 1,000 metres (3,280 ft) into the waters of the Karrat Fjord. The event was thought to be caused by melting ice that destabilised the rock. It registered as a magnitude 4.1 earthquake and created a 100-metre (328 ft) wave. The settlement of Nuugaatsiaq, 32 kilometres (20 mi) away, saw run-up heights of 9 metres (30 ft). Eleven buildings were swept into the sea, four people died, and 170 residents of Nuugaatsiaq and Illorsuit were evacuated because of a danger of additional landslides and waves. The tsunami was noted at settlements as far as 100 kilometres (62 mi) away.