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Megatsunami (often hyphenated as mega-tsunami, also known as iminami or "wave of purification") is an informal term used mostly by popular media and popular scientific societies to describe a very large tsunami wave beyond the typical size reached by most tsunamis. A megatsunami is associated with waves beyond the norm for tsunamis, ranging from over 40 metres (131 feet) to giants over 100 metres (328 ft) tall. Note that the waves are often much higher when they meet land, as the water often floods upwards from the force of impact. Image File history File linksMetadata Megatsunami-coast. ...
For other uses, see Tsunami (disambiguation). ...
A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ...
Megatsunamis are caused by a very large impact or landslide into a body of water when the water cannot disperse in all directions. For this reason, they are usually a highly localized effect, either occurring when the origin of a tsunami is extremely close to the shore, or in deep, narrow inlets, lakes or other water passages. Artists impression of a major impact event. ...
This article is about geological phenomenon. ...
General information
The astounding heights quoted for megatsunami waves are caused by the displacement of a very large volume of water in a limited space in a very short time creating a single powerful surge.
Megatsunamis may be caused by landslide and rockfall phenomena, explosive volcanic events, or meteor impacts. Underwater earthquakes do not normally generate such large tsunamis; typically tsunamis caused by earthquakes (such as the 2004 Indian Ocean earthquake) have a height of less than ten metres at the shore (depending on how much water was displaced by the earthquake and on various natural factors such as tree cover and the general shore characteristics) but can affect thousands of kilometres of coastline and reach many kilometres inland. Artists impression of a major impact event. ...
This article is about the natural seismic phenomenon. ...
The 2004 Indian Ocean earthquake, known by the scientific community as the Sumatra-Andaman earthquake,[1] was a great undersea earthquake that occurred at 00:58:53 UTC (07:58:53 local time) December 26, 2004 with an epicentre off the west coast of Sumatra, Indonesia. ...
Discovery and confirmation of existence Megatsunamis were first hypothesized by geologists searching for oil in Alaska in 1953[1]. They observed that in Lituya Bay mature forestation did not extend to the shoreline as it did in nearly all other bays in the region. Rather, there were bands of younger trees closer to the shore. The surveyors called the boundary between these bands a trim line, resembling those caused by the advance and retreat of glaciers. Selected trees were cut in the areas just above and below each trim line. The trees just above these lines showed severe scarring, as if hit very hard by something that came from the coast. The only possible explanation, according to scientists, was that there had been unusually large waves in the deep inle. This is a recently deglaciated fjord with steep slopes and crossed by a major fault. The topology of the inlet is particularly suited to producing landslide generated tsunamis. They speculated that something had caused a huge wave in relatively recent times, but the cause of this hypothetical wave remained unknown. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ...
For other uses, see Alaska (disambiguation). ...
Lituya Bay is a fjord located at in the U.S. state of Alaska. ...
A trim line making the previous height of Tana Glacier in Alsaka A trim line (or trimline) is a clear line on the side of a valley formed by a glacier. ...
Fjord in Sunnmøre, Norway Geirangerfjord, Norway A fjord (or fiord) is a long, narrow estuary with steep sides, made when a glacial valley is filled by rising sea water levels. ...
On July 10, 1958 the speculation was confirmed, following a nearby earthquake of magnitude 7.7, which generated a landslide that sent water surging across Lituya Bay. The landslide hit the water fast enough to shoot water up the opposite bay to a height of 524 meters. A wave with initial heights of about 333 meters traveled along the bay, and flowed over the entrance to the bay with a height of about 350 meters. Howard Ulrich and his son, Howard Jr. were in the bay in their fishing boat when they saw the wave. Ulrich tried to get over the wave and he and his son amazingly survived the wave, and reported that it carried their boat "over the trees". Another boat actually rode over the tsunami in the bay, and one was destroyed by the tsunami. is the 191st day of the year (192nd in leap years) in the Gregorian calendar. ...
Jan. ...
Lituya Bay is a fjord located at in the U.S. state of Alaska. ...
Known megatsunamis
Recent Lituya Bay Tsunami -
On July 10, 1958, a landslide caused by an earthquake generated a monstrous tsunami 524m (1720 ft) high, which stripped trees and soil from the opposite headland and consumed the entire bay, destroying three fishing boats anchored there and killing two people. Lituya Bay is a fjord located at in the U.S. state of Alaska. ...
Vajont Dam
 The Vajont Dam as seen from Longarone today, showing approximately the top 60-70 metres of concrete. The 200-250 metre megatsunami that over-topped the dam would have obscured virtually all of the sky in this picture. -
On October 9, 1963, a landslide above Vajont Dam in Italy produced a 250m (820 ft) tsunami that overtopped the dam and destroyed the villages of Longarone, Pirago, Rivalta, Villanova and Faè, killing almost 2,000 people. Image File history File links Size of this preview: 423 × 600 pixel Image in higher resolution (1625 × 2304 pixel, file size: 693 KB, MIME type: image/jpeg) La diga del Vajont vista da Longarone. ...
Image File history File links Size of this preview: 423 × 600 pixel Image in higher resolution (1625 × 2304 pixel, file size: 693 KB, MIME type: image/jpeg) La diga del Vajont vista da Longarone. ...
Vajont Dam is a dam completed in 1961 under Mount Toc, 100 km north of Venice, Italy. ...
Longarone is a town and commune on the banks of the Piave in province of Belluno in North-East Italy. ...
Vajont Dam is a dam completed in 1961 under Mount Toc, 100 km north of Venice, Italy. ...
is the 282nd day of the year (283rd in leap years) in the Gregorian calendar. ...
For other uses, see 1963 (disambiguation). ...
Longarone is a town and commune on the banks of the Piave in province of Belluno in North-East Italy. ...
Spirit Lake Tsunami
On May 18, 1980, the upper 1,500 feet (460 m) including the former summit of Mount St. Helens, a volcano in Washington state, detached as a landslide. The avalanche slammed into Spirit Lake sending a tsunami surging around the lake basin as high as 820 feet (250 m) above lake level. Above the upper limit of the tsunami, trees lie where they were knocked down by a pyroclastic surge; below the limit, the downed trees and the surge deposits were removed by the tsunami and deposited in Spirit Lake.[2] For the mountain in California, see Mount Saint Helena. ...
Cleveland Volcano in the Aleutian Islands of Alaska photographed from the International Space Station For other uses, see Volcano (disambiguation). ...
For the capital city of the United States, see Washington, D.C.. For other uses, see Washington (disambiguation). ...
This article is about geological phenomenon. ...
Photograph taken on October 4, 1980 Spirit Lake was formerly an attractive lake near Mount St. ...
For other uses, see Tsunami (disambiguation). ...
This article does not adequately cite its references or sources. ...
Historical The geological record suggests that megatsunamis generated by the collapse of flank of a volcanic island, their most common cause, may occur every few thousand years [3]. Their size and power can produce devastating effects; travelling across oceans and reshaping entire coastlines. The most recent such event so far known occurred approximately 4,000 years ago on Réunion island, to the east of Madagascar. [4] The most recent collapse occurred on Ritter Island in 1888 but it only generated 12-15 metre waves, which, although they killed 3,000 people on surrounding islands, were not megatsunamis and did not cause widespread devastation. Ritter Island is a small crescent-shaped volcanic island 100 kilometres northeast of New Guinea, situated between Umboi Island and Sakar Island. ...
The most recent megatsunamis, such as the one at Lituya Bay in 1958 and in the Vajont Dam in 1963, have occurred as a result of landslides in largely enclosed bodies of waters and their effects have been limited. Lituya Bay is a fjord located at in the U.S. state of Alaska. ...
Vajont Dam is a dam completed in 1961 under Mount Toc, 100 km north of Venice, Italy. ...
Other recent megatsunamis include the 40 metre high waves generated by the collapse of Krakatoa during its eruption in 1883 which killed 36,000 people on Java, Sumatra and the small islands around them; and the collapse of much of Santorini during its cataclysmic eruption around 3,500 years ago which produced a 100-150 metre wave that struck the north coast of Crete after travelling 70 kilometres. However, these megatsunamis did not propagate thousands of miles to cause more widespread damage, in part leading to the controversy about whether the waves produced by island collapses travel great distances in the same way that tsunamis do.[5] For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ...
This article is about the Java island. ...
Sumatra (also spelled Sumatera) is the sixth largest island in the world (approximately 470,000 km²) and is the largest island entirely in Indonesia (two larger islands, Borneo and New Guinea, are partially in Indonesia). ...
Santorini (Greek ΣαντοÏίνη, IPA: ) is a small, circular archipelago of volcanic islands located in southern Aegean Sea, about 200 km south-east from Greeces mainland. ...
For other uses, see Crete (disambiguation). ...
Prehistoric In the Norwegian Sea, the Storegga Slide caused a megatsunami 7,000 years ago. Extensive geological investigations indicate that the risk of a re-occurrence is minimal. The Norwegian Sea (Norwegian: Norskehavet) is part of the North Atlantic Ocean northwest of Norway, located between the North Sea (i. ...
The three Storegga Slides count among the largest recorded landslides. ...
There is evidence of a megatsunami-type freshwater disaster that occurred 10,000 to 20,000 years ago can be seen at Seton Portage, British Columbia (not far north of Harrison Lake) where a huge chunk of the Cayoosh Range suddenly slid north into what had been a large lake spanning the area from Lillooet, British Columbia to near Birken, in the Gates Valley or Pemberton Pass to the southwest. The event has not been studied much in modern times but the proto-lake must have been at least as deep as its two present-day halves, Seton and Anderson Lakes, on either side of the Portage, suggesting that the wave created by the giant landslide must have been comparable to Lituya Bay. View of Seton Portage from Mission Mountain, c. ...
Harrison Lake is the largest lake in the southern Coast Mountains, being about 25,000 ha (2500 sq km or 965 sq mi) in area. ...
The Cayoosh Range is the northernmost section of the Lillooet Ranges, which are a subrange of the Pacific Ranges of the Coast Mountains in British Columbia. ...
Lillooet (formerly Cayoosh Flat) is a small but historic and highly scenic community on the Fraser River in western Canada, about 240 kilometres (150 miles) up the British Columbia Railway line from Vancouver. ...
Seton Lake is a freshwater fjord draining into the Fraser River at the town of Lillooet, British Columbia, about 22 km long and 243 m in elevation and 26. ...
Anderson Lake is located about 25 miles west of the town of Lillooet, British Columbia and is about 285 sq km (100 sq mi) in area and around 21 km (13 mi) in length. ...
View of Seton Portage from Mission Mountain, c. ...
This article is about geological phenomenon. ...
Lituya Bay is a fjord located at in the U.S. state of Alaska. ...
They have also been generated by bolide impacts. There are indications that a giant tsunami was generated by the bolide impact that created the Chesapeake Bay impact crater, a shallow-water near-shore impact off the eastern North American coastline about 35.5 million years ago, in the late Eocene Epoch. The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ...
The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ...
The Chesapeake Bay Impact Crater was formed by the impact of an extraterrestrial bolide that hit about 35. ...
hfajhfiudshfas == == == --24. ...
// For other uses, see time scale. ...
The meteor which created the Chicxulub Crater in Yucatan around 65 million years ago (and probably triggered the dinosaurs' extinction) may have generated the largest megatsunamis in Earth's history. Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...
Radar topography reveals the 180 kilometer (112 mile) wide ring of the crater (image courtesy NASA/JPL-Caltech) Chicxulub Crater (IPA: ) (cheek-shoo-LOOB) is an ancient impact crater buried underneath the Yucatán Peninsula, with its center located approximately underneath the town of Chicxulub, Yucatán, Mexico. ...
The Yucatán Peninsula separates the Caribbean Sea from the Gulf of Mexico. ...
Megatsunami threats Volcanic islands (such as Réunion and the Hawaiian Islands) can cause megatsunamis to hit other nearby islands in the same chain because often they are comparatively steep sloped structures with little horizontal support made up of often loosely aggregated material heaped up by successive eruptions from a central vent area and bisected by faults and stress lines created by ongoing vulcanism. Evidence for large landslides has been found in the form of extensive underwater debris aprons around them composed of the material which has slipped into the ocean. In recent years five such debris aprons have been found in the Hawaiian Islands alone. Map of the Hawaiian Islands, a chain of islands that stretches 2,400 km in a northwesterly direction from the southern tip of the Island of Hawaii. ...
Some geologists speculate that the most likely candidate for the source of the next large-scale megatsunami is the island of La Palma, in the Canary Islands. Reports say that during the 1949 eruption the western half of the Cumbre Vieja ridge slipped four metres downwards into the Atlantic Ocean, though this is disputed. It is believed that this process was driven by the pressure caused by the rising magma heating and vaporising water trapped within the structure of the island, causing the island's structure to be pushed apart. The island is still considered active, though quiescent at present, but it is expected to erupt again some time in the next few hundred years. Were this to happen it is speculated that a megatsunami would be created as the western half of the island, weighing perhaps 500 billion tonnes, catastrophically slides into the ocean in a single event, causing local wave heights of hundreds of metres and a likely height of around 10–25 m at the Caribbean and the Eastern North American seaboard coast several hours later. However, this is speculative since there is disagreement whether it would in fact happen, when, or how likely it is. This article is about one of the Canary Islands. ...
Anthem: Arrorró Capital Las Palmas de Gran Canaria and Santa Cruz de Tenerife Official language(s) Spanish Area – Total – % of Spain Ranked 13th 7,447 km² 1. ...
Cumbre Vieja (Spanish: Old Summit) is a volcanic ridge on the island of La Palma in Spains Canary Islands. ...
Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ...
West Indies redirects here. ...
North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ...
There is also disagreement among scientists about whether an eruption of Cumbre Vieja would cause a single large landslide or a series of smaller landslides and if such a landslide would generate a tsunami capable of crossing the Atlantic. The Tsunami Society issued a statement in 2003 that such collapses are rare and occur at intervals of thousands or millions of years, that the risk of La Palma collapsing was over-dramatized, and that although the catastrophic collapse of the islands of Krakatoa and Santorini produced megatsunamis in the local region, huge waves did not propagate across oceans to cause similar devastation on more distant coasts, adding that evidence (including computer simulations and experiments with models) suggests this type of wave does not travel great distances in the same way that normal tsunamis do. [6] The Tsunami Society is a research organization that studies tsunamis and seeks to supply information about them to the public. ...
This article is about one of the Canary Islands. ...
For the 1969 film about the Krakatoa eruption, see Krakatoa, East of Java. ...
Santorini (Greek ΣαντοÏίνη, IPA: ) is a small, circular archipelago of volcanic islands located in southern Aegean Sea, about 200 km south-east from Greeces mainland. ...
It has been suggested that simulation software be merged into this article or section. ...
Besides fjords in Alaska, many locations face threats of localized, but still potentially dangerous, megatsunami-type waves. Some geologists speculate that an unstable rock face at Mount Breakenridge above the north end of the giant fresh-water fjord of Harrison Lake in the Fraser Valley in southwestern British Columbia could collapse into the lake, generating a large wave that might destroy the town of Harrison Hot Springs at the south end. Lysefjorden in Norway A fjord (pronounced FEE-ord or fyord, SAMPA: [fi:3:d] or [faI3:d]; sometimes written fiord) is a glacially overdeepened valley, usually narrow and steep-sided, extending below sea level and filled with salt water. ...
Harrison Lake is the largest lake in the southern Coast Mountains, being about 25,000 ha (2500 sq km or 965 sq mi) in area. ...
Fraser Valley is the section of the Fraser River basin in southwestern British Columbia downstream of the Fraser Canyon. ...
Motto: Splendor sine occasu (Latin: Splendour without diminishment) Capital Victoria Largest city Vancouver Official languages English (de facto) Government Lieutenant-Governor Steven Point Premier Gordon Campbell (BC Liberal) Federal representation in Canadian Parliament House seats 36 Senate seats 6 Confederation July 20, 1871 (6th province) Area Ranked 5th Total 944...
Harrison Hot Springs is a small community on the southern end of Harrison Lake in the Fraser Valley of British Columbia. ...
Movies Fictional megatsunamis are a favourite subject of many films, given their undoubted visual impact; these megatsunamis are often caused by bolide impacts, extraterrestrial causes and other dramatic causes, rather than by landslides. Examples of this are the movies Deep Impact and the director's cut of The Abyss. For other uses, see Fiction (disambiguation). ...
This article is about motion pictures. ...
The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ...
Deep Impact is a 1998 disaster film/science fiction film released by Paramount Pictures and DreamWorks Pictures. ...
A directors cut is a specially edited version of a film, and less often TV series, music video, commercials or video games, that is supposed to represent the directors own approved edit. ...
The Abyss is a 1989 science fiction film which was written and directed by James Cameron, starring Ed Harris, Mary Elizabeth Mastrantonio, and Michael Biehn. ...
See also A supervolcano is a volcano that produces the largest and most voluminous kinds of eruption on Earth. ...
This article is about one of the Canary Islands. ...
Satellite image of Thera The Bronze Age Minoan eruption of Thera (or Santorini) is considered to be one of the largest volcanic eruptions on Earth during the period of written human history. ...
For other uses, see Disaster (disambiguation). ...
References - ^ Don J. Miller, "Giant Waves in Lituya Bay, Alaska"
- ^ USGS Website. Geology of Interactions of Volcanoes, Snow, and Water: Tsunami on Spirit Lake early during 18 May 1980 eruption
- ^ Mega-tsunami: Wave of Destruction. Transcript. BBC Two television programme, first broadcast 12 October 2000
- ^ Mega-tsunami: Wave of Destruction. Background article. BBC Two television programme first broadcast 12 October 2000
- ^ Surfing the Wave, Leslie Mullen, Astrobiology Magazine, 13 September 2004
- ^ Mega Tsunami hazards, The Tsunami Society, 15 January 2003
Further reading - Evaluation of the Threat of Mega Tsumami Generation from Postulated Massive Slope Failure of Island Stratovolcanoes on La Palma, Canary Islands, and on The Island of Hawaii, George Pararas-Carayannis, Science of Tsunami Hazards, Vol 20, No.5, pages 251-277, 2002.
- Ward, S.N. and Day, S. 2001. Cumbre Vieja Volcano — Potential collapse and tsunami at La Palma, Canary Islands. Geophysical Research Letters, 28, 17 pp. 3397–3400.
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