Megatsunami - wikipedia Megatsunami Jump to : navigation , search Diagram of the 1958 Lituya Bay megatsunami , which proved the existence of megatsunamis . A megatsunami is a very large wave created by a large , sudden displacement of material into a body of water . Megatsunamis have quite different features from other , more usual types of tsunamis . Most tsunamis are caused by underwater tectonic activity ( movement of the earth 's plates ) and therefore occur along plate boundaries and as a result of earthquake and rise or fall in the sea floor , causing water to be displaced . Ordinary tsunamis have shallow waves out at sea , and the water piles up to a wave height of up to about 10 metres ( 33 feet ) as the sea floor becomes shallow near land . By contrast , megatsunamis occur when a very large amount of material suddenly falls into water or anywhere near water ( such as via a meteor impact ) , or are caused by volcanic activity . They can have extremely high initial wave heights of hundreds and possibly thousands of metres , far beyond any ordinary tsunami , as the water is `` splashed '' upwards and outwards by the impact or displacement . As a result , two heights are sometimes quoted for megatsunamis -- the height of the wave itself ( in water ) , and the height to which it surges when it reaches land , which depending upon the locale , can be several times larger . Modern megatsunamis include the one associated with the 1883 eruption of Krakatoa ( volcanic eruption ) , the 1958 Lituya Bay megatsunami ( landslide into a bay ) , and the wave resulting from the Vajont Dam landslide ( caused by human activity destabilizing sides of valley ) . Prehistoric examples include the Storegga Slide ( landslide ) , and the Chicxulub , Chesapeake Bay and Eltanin meteor impacts . Contents ( hide ) 1 Overview 2 Recognition of the concept of megatsunami 3 Analysis of mechanism 4 List of megatsunamis 4.1 Prehistoric 4.2 Historic 4.2. 1 ca 1600 BC : Santorini 4.2. 2 1792 : Mount Unzen , Japan 4.2. 3 1883 : Krakatoa 4.2. 4 1958 : Lituya Bay , Alaska , US 4.2. 5 1963 : Vajont Dam , Italy 4.2. 6 1980 : Spirit Lake , Washington , US 5 Potential future megatsunamis 5.1 British Columbia 5.2 Canary Islands 5.3 Hawaii 5.4 Cape Verde Islands 6 See also 7 References 8 Further reading 9 External links Overview ( edit ) A megatsunami is a tsunami -- a large wave due to displacement of a body of water -- with an initial wave amplitude ( height ) measured in several tens , hundreds , or possibly thousands of metres . Normal tsunamis generated at sea result from movement of the sea floor . They have a small wave height offshore , are very long ( often hundreds of kilometres ) , and generally pass unnoticed at sea , forming only a slight swell usually of the order of 30 cm ( 12 in ) above the normal sea surface . When they reach land , the wave height increases dramatically as the base of the wave pushes the water column above it upwards . By contrast , megatsunamis are caused by giant landslides and other impact events . This could also refer to a meteorite hitting an ocean . Underwater earthquakes or volcanic eruptions do not normally generate such large tsunamis , but landslides next to bodies of water resulting from earthquakes can , since they cause a large amount of displacement . If the landslide or impact occurs in a limited body of water , as happened at the Vajont Dam ( 1963 ) and Lituya Bay ( 1958 ) then the water may be unable to disperse and one or more exceedingly large waves may result . A way to visualize the difference , is that an ordinary tsunami is caused by sea floor changes , somewhat like pushing up on the floor of a large tub of water to the point it overflows , and causing a surge of water to `` run off '' at the sides . In this analogy , a megatsunami would be more similar to dropping a large rock from a considerable height into the tub , at one end , causing water to splash up and out , and overflow at the other end . Two heights are sometimes quoted for megatsunamis -- the height of the wave itself ( in water ) , and the height to which it surges when it reaches land , which depending upon the locale , can be several times larger . Recognition of the concept of megatsunami ( edit ) Main article : 1958 Lituya Bay megatsunami Geologists searching for oil in Alaska in 1953 observed that in Lituya Bay , mature tree growth did not extend to the shoreline as it did in many other bays in the region . Rather , there was a band of younger trees closer to the shore . Forestry workers , glaciologists , and geographers call the boundary between these bands a trim line . Trees just above the trim line showed severe scarring on their seaward side , whilst those from below the trim line did not . The scientists hypothesized that there had been an unusually large wave or waves in the deep inlet . Because this is a recently deglaciated fjord with steep slopes and crossed by a major fault , one possibility was a landslide - generated tsunami . On 9 July 1958 , a 7.8 M strike - slip earthquake in southeast Alaska caused 90 million tonnes of rock and ice to drop into the deep water at the head of Lituya Bay . The block fell almost vertically and hit the water with sufficient force to create a wave that surged up the opposite side of the head of the bay to a height of 1720 feet ( 524 m ) , and was still many tens of metres high further down the bay , when it carried eyewitnesses Howard Ulrich and his son Howard Jr. over the trees in their fishing boat . They were washed back into the bay and both survived . Analysis of mechanism ( edit ) The mechanism giving rise to megatsunamis was analysed for the Lituya Bay event in a study presented at the Tsunami Society in 1999 ; this model was considerably developed and modified by a second study in 2010 . Although the earthquake which caused the megatsunami was considered very energetic , and involving strong ground movements , several possible mechanisms were not likely or able to have caused the resulting megatsunami . Neither water drainage from a lake , nor landslide , nor the force of the earthquake itself led to the megatsunami , although all of these may have contributed . Instead , the megatsunami was caused by a massive and sudden impulsive impact when about 40 million cubic yards of rock several hundred metres above the bay was fractured from the side of the bay , by the earthquake , and fell `` practically as a monolithic unit '' down the almost vertical slope and into the bay . The rockfall also caused air to be `` dragged along '' due to viscosity effects , which added to the volume of displacement , and further impacted the sediment on the floor of the bay , creating a large crater . The study concluded that : `` The giant wave runup of 1,720 feet ( 524 m . ) at the head of the Bay and the subsequent huge wave along the main body of Lituya Bay which occurred on July 9 , 1958 , were caused primarily by an enormous subaerial rockfall into Gilbert Inlet at the head of Lituya Bay , triggered by dynamic earthquake ground motions along the Fairweather Fault . The large mass of rock , acted as a monolith ( thus resembling high - angle asteroid impact ) , struck with great force the sediments at bottom of Gilbert Inlet at the head of the bay . The impact created a large crater and displaced and folded recent and Tertiary deposits and sedimentary layers to an unknown depth . The displaced water and the displacement and folding of the sediments broke and uplifted 1,300 feet of ice along the entire front of the Lituya Glacier at the north end of Gilbert Inlet . Also , the impact and the sediment displacement by the rockfall resulted in an air bubble and in water splashing action that reached the 1,720 foot ( 524 m . ) elevation on the other side of the head of Gilbert Inlet . The same rockfall impact , in combination with the strong ground movements , the net vertical crustal uplift of about 3.5 feet , and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated , generated the giant solitary gravity wave which swept the main body of the bay . This was the most likely scenario of the event -- the '' PC model '' that was adopted for subsequent mathematical modeling studies with source dimensions and parameters provided as input . Subsequent mathematical modeling at the Los Alamos National Laboratory ( Mader , 1999 , Mader & Gittings , 2002 ) supported the proposed mechanism -- as there was indeed sufficient volume of water and an adequately deep layer of sediments in the Lituya Bay inlet to account for the giant wave runup and the subsequent inundation . The modeling reproduced the documented physical observations of runup . '' A 2010 model examined the amount of infill on the floor of the bay , which was many times larger than that of the rockfall alone , and also the energy and height of the waves , and the accounts given by eyewitnesses , concluded that there had been a `` dual slide '' involving a rockfall , which also triggered a release of 5 to 10 times its volume of sediment trapped by the adjacent Lituya Glacier , as an almost immediate and many times larger second slide , a ratio comparable with other events where this `` dual slide '' effect is known to have happened . List of megatsunamis ( edit ) Prehistoric ( edit ) The asteroid linked to the extinction of dinosaurs , which created the Chicxulub crater in Yucatán approximately 66 million years ago , would have caused an over 100 metres ( 330 ft ) tall megatsunami . The height of the tsunami was limited due to relatively shallow sea in the area of the impact ; in deep sea it would be 4.6 kilometres ( 2.9 mi ) tall . A series of megatsunamis were generated by the bolide impact that created the Chesapeake Bay impact crater , about 35.5 million years ago . During the Messinian the coasts of northern Chile were likely struck by various megatsunamis . A megatsunami affected the coast of south -- central Chile in the Pliocene as evidenced by the sedimentary record of Ranquil Formation . The Eltanin impact in the southeast Pacific Ocean 2.5 million years ago caused a megatsunami that was over 200 m ( 660 ft ) high in southern Chile and the Antarctic Peninsula ; the wave swept across much of the Pacific Ocean . The northern half of the East Molokai Volcano suffered a catastrophic collapse and likely megatsunami about 1.5 million years ago and now lies as a debris field scattered northward across the ocean bottom , while what remains on the island are the highest sea cliffs in the world . The existence of large scattered boulders in only one of the four marine terraces of Herradura Bay south of the Chilean city of Coquimbo has been interpreted by Roland Paskoff as the result of a mega-tsunami that occurred in the Middle Pleistocene . A massive collapse of the western edge of the Lake Tahoe basin , which formed McKinney Bay around 50,000 years ago , is thought to have generated a tsunami / seiche wave with a height approaching 330 ft ( 100 m ) . In the North Sea , the Storegga Slide caused a megatsunami approximately 8,200 years ago . It is estimated to have completely flooded the remainder of Doggerland . Approximately 8,000 years ago , a massive volcanic landslide off Mt . Etna , Sicily caused a megatsunami which devastated the eastern Mediterranean coastline on three continents . Wave heights on the coast of Calabria are estimated to have reached a maximum of 40m . Approximately 4,000 years ago , a landslide on Réunion island , to the east of Madagascar , may have caused a megatsunami . Historic ( edit ) Ca 1600 bc : santorini ( edit ) Main article : Minoan eruption 3,600 years ago , the Thera volcano erupted , the force of the eruption causing megatsunamis which affected the whole Aegean sea and the eastern Mediterranean sea . 1792 : Mount Unzen , Japan ( edit ) Main article : 1792 Unzen earthquake and tsunami In 1792 , Mount Unzen in Japan erupted , causing part of the volcano to collapse into the sea . The landslide caused a megatsunami that reached 100 metres ( 330 ft ) high and killed 15,000 people in the local fishing villages . 1883 : Krakatoa ( edit ) Main article : 1883 eruption of Krakatoa § Tsunamis and distant effects The eruption of Krakatoa created pyroclastic flows which generated megatsunamis when they hit the waters of the Sunda Strait on 27 August 1883 . The waves reached heights of up to 24 metres ( 79 feet ) along the south coast of Sumatra and up to 42 metres ( 138 feet ) along the west coast of Java . 1958 : Lituya Bay , Alaska , us ( edit ) Main articles : 1958 Lituya Bay megatsunami and Lituya Bay Damage from the 1958 Lituya Bay megatsunami can be seen in this oblique aerial photograph of Lituya Bay , Alaska as the lighter areas at the shore where trees have been stripped away . On July 9 , 1958 , a giant landslide at the head of Lituya Bay in Alaska , caused by an earthquake , generated a wave that washed out trees to a maximum altitude of 520 metres ( 1,710 ft ) at the entrance of Gilbert Inlet . The wave surged over the headland , stripping trees and soil down to bedrock , and surged along the fjord which forms Lituya Bay , destroying a fishing boat anchored there and killing two people . Howard Ulrich and his son managed to ride the wave in their boat , and both survived . 1963 : Vajont Dam , Italy ( edit ) Main article : Vajont Dam On October 9 , 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 . 1980 : Spirit Lake , Washington , us ( edit ) Main articles : Spirit Lake ( Washington ) , 1980 eruption of Mount St. Helens , and Mount St. Helens On May 18 , 1980 , the upper 460 metres ( 1,509 feet ) of Mount St. Helens collapsed , creating a massive 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 ( 853 feet ) above the pre-eruption water level ( ~ 975 m asl / 3,199 ft ) . 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 . Potential future megatsunamis ( edit ) Experts interviewed by the BBC think that a massive landslide on a volcanic ocean island is the most likely future cause of a megatsunami . The size and power of a wave generated by such means could produce devastating effects , travelling across oceans and inundating up to 25 kilometres ( 16 mi ) inland from the coast . British Columbia ( edit ) Some geologists consider an unstable rock face at Mount Breakenridge , above the north end of the giant fresh - water fjord of Harrison Lake in the Fraser Valley of southwestern British Columbia , Canada , to be unstable enough to collapse into the lake , generating a megatsunami that might destroy the town of Harrison Hot Springs ( located at its south end ) . Canary Islands ( edit ) Geologists Dr. Simon Day and Dr. Steven Neal Ward consider that a megatsunami could be generated during an eruption of Cumbre Vieja on the volcanic ocean island of La Palma , in the Canary Islands , Spain . In 1949 , this volcano erupted at its Duraznero , Hoyo Negro and Llano del Banco vents , and there was an earthquake with an epicentre near the village of Jedey . The next day Juan Bonelli Rubio , a local geologist , visited the summit area and found that a fissure about 2.5 kilometres ( 1.6 mi ) long had opened on the east side of the summit . As a result , the west half of the volcano ( which is the volcanically active arm of a triple - armed rift ) had slipped about 2 metres ( 6.6 ft ) downwards and 1 metre ( 3.3 ft ) westwards towards the Atlantic Ocean , Cumbre Vieja is currently dormant , but will almost certainly erupt again . Day and Ward hypothesize that if such an eruption causes the western flank to fail , a mega-tsunami could be generated . La Palma is currently the most volcanically active island in the Canary Islands Archipelago . It is likely that several eruptions would be required before failure would occur on Cumbre Vieja . However , the western half of the volcano has an approximate volume of 500 cubic kilometres ( 120 cu mi ) and an estimated mass of 1.5 trillion metric tons ( 1.7 × 10 short tons ) . If it were to catastrophically slide into the ocean , it could generate a wave with an initial height of about 1,000 metres ( 3,300 ft ) at the island , and a likely height of around 50 metres ( 164 ft ) at the Caribbean and the Eastern North American seaboard when it runs ashore eight or more hours later . Tens of millions of lives could be lost in the cities and / or towns of St. John 's , Halifax , Boston , New York , Baltimore , Washington , D.C. , Miami , Havana and the rest of the Eastern Coasts of the United States and Canada , as well as many other cities on the Atlantic coast in Europe , South America and Africa . The likelihood of this happening is a matter of vigorous debate . The last eruption on the Cumbre Vieja occurred in 1971 at the Teneguia vent at the southern end of the sub-aerial section without any movement . The section affected by the 1949 eruption is currently stationary and does not appear to have moved since the initial rupture . Geologists and volcanologists are in sharp disagreement about whether an eruption on the Cumbre Vieja would cause a single large gravitational landslide or a series of smaller landslides , or whether a slide is likely at all . There are also questions about the dynamics . Day and Ward have admitted that their original analysis of the danger was based on several worst case assumptions . Hawaii ( edit ) Sharp cliffs and associated ocean debris at the Kohala Volcano , Lanai and Molokai indicate that landslides from the flank of the Kilauea and Mauna Loa volcanoes in Hawaii may have triggered past megatsunamis , most recently at 120,000 BP . A tsunami event is also possible , with the tsunami potentially reaching up to about 1 kilometre ( 3,300 ft ) in height . According to the documentary National Geographic 's Ultimate Disaster : Tsunami , if a big landslide occurred at Mauna Loa or the Hilina Slump , a 30 - metre ( 98 ft ) tsunami would take only thirty minutes to reach Honolulu , Hawaii . There , hundreds of thousands of people could be killed as the tsunami could level Honolulu and travel 25 kilometres ( 16 mi ) inland . Also , the West Coast of America and the entire Pacific Rim could potentially be affected . Cape Verde Islands ( edit ) Steep cliffs on the Cape Verde Islands have been caused by catastrophic debris avalanches . These have been common on the submerged flanks of ocean island volcanoes and more can be expected in the future . See also ( edit ) 2004 Indian Ocean earthquake and tsunami Cumbre Vieja La Palma List of historical tsunamis Minoan eruption Tsunamis in lakes References ( edit ) ^ Jump up to : Miller , Don J. `` Giant Waves in Lituya Bay , Alaska '' . uwsp.edu . p. 3 . Archived from the original on 13 October 2013 . ^ Jump up to : The Mega-Tsunami of July 9 , 1958 in Lituya Bay , Alaska : Analysis of Mechanism -- George Pararas - Carayannis , Excerpts from Presentation at the Tsunami Symposium of Tsunami Society of May 25 -- 27 , 1999 , in Honolulu , Hawaii , USA Jump up ^ Ward , Steven N. ; Day , Simon ( 2010 ) . `` Lituya Bay Landslide and Tsunami -- A Tsunami Ball Approach '' ( PDF ) . Journal of Earthquake and Tsunami. 4 ( 4 ) : 285 -- 319 . doi : 10.1142 / S1793431110000893 . Jump up ^ Bryant , Edward ( June 2014 ) . Tsunami : The Underrated Hazard . Springer . p. 178 . ISBN 978 - 3 - 319 - 06133 - 7 . Jump up ^ Poag , C.W. ( 1997 ) . `` The Chesapeake Bay bolide impact : A convulsive event in Atlantic Coastal Plain evolution '' . Sedimentary Geology. 108 ( 1 -- 4 ) : 45 -- 90 . Bibcode : 1997SedG ... 108 ... 45P . doi : 10.1016 / S0037 - 0738 ( 96 ) 00048 - 6 . Jump up ^ Le Roux , Jacobus P. ( 2015 ) . `` A critical examination of evidence used to re-interpret the Hornitos mega-breccia as a mass - flow deposit caused by cliff failure '' . Andean Geology. 41 ( 1 ) : 139 -- 145 . Jump up ^ Le Roux , J.P. ; Nielsen , Sven N. ; Kemnitz , Helga ; Henriquez , Álvaro ( 2008 ) . `` A Pliocene mega-tsunami deposit and associated features in the Ranquil Formation , southern Chile '' ( PDF ) . Sedimentary Geology. 203 ( 1 ) : 164 -- 180 . Bibcode : 2008SedG ... 203 ... 164L . doi : 10.1016 / j. sedgeo. 2007.12. 002 . Retrieved 11 April 2016 . Jump up ^ `` Hawaiian landslides have been catastrophic '' . mbari.org . Monterey Bay Aquarium Research Institute . Jump up ^ Culliney , John L. ( 2006 ) Islands in a Far Sea : The Fate of Nature in Hawaii . Honolulu : University of Hawaii Press . p. 17 . Jump up ^ Paskoff , Roland ( 1991 ) . `` Likely occurrence of mega-tsunami in the Middle Pleistocene near Coquimbo , Chile '' . Revista geológica de Chile . 18 ( 1 ) : 87 -- 91 . Retrieved 17 July 2016 . Jump up ^ Gardner , J.V. ( July 2000 ) . `` The Lake Tahoe debris avalanche '' . 15th Annual Geological Conference . Geological Society of Australia . Jump up ^ Bondevik , S. ; Lovholt , F. ; Harbitz , C. ; Mangerud , J. ; Dawsond , A. ; Svendsen , J.I. ( 2005 ) . `` The Storegga Slide tsunami -- comparing field observations with numerical simulations '' . Marine and Petroleum Geology. 22 ( 1 -- 2 ) : 195 -- 208 . doi : 10.1016 / j. marpetgeo. 2004.10. 003 . Jump up ^ Rincon , Paul ( 1 May 2014 ) . `` Prehistoric North Sea ' Atlantis ' hit by 5m tsunami '' . Retrieved 22 February 2017 -- via www.bbc.com . Jump up ^ Pareschi , M.T. ; Boschi , E. ; Favalli , M. ( 2006 ) . `` Lost tsunami '' . Geophysical Research Letters. 33 ( 22 ) : L22608 . Bibcode : 2006GeoRL ... 3322608P . doi : 10.1029 / 2006GL027790 . Jump up ^ `` Mega-tsunami : Wave of Destruction '' . BBC Two . 12 October 2000 . Jump up ^ Bryant , Edward , Tsunami : The Underrated Hazard , Springer : New York , 2014 , ISBN 978 - 3 - 319 - 06132 - 0 , pp. 162 -- 163 . Jump up ^ Mader , Charles L. ; Gittings , Michael L. ( 2002 ) . `` Modeling the 1958 Lituya Bay Mega-Tsunami , II '' ( PDF ) . Science of Tsunami Hazards. 20 ( 5 ) : 241 -- 250 . Jump up ^ `` Archived copy '' . Archived from the original on 2009 - 07 - 29 . Retrieved 2009 - 07 - 29 . Vaiont Dam photos and virtual field trip ( University of Wisconsin ) , retrieved 2009 - 07 - 01 Jump up ^ Voight et al. 1983 Jump up ^ USGS Website . Geology of Interactions of Volcanoes , Snow , and Water : Tsunami on Spirit Lake early during 18 May 1980 eruption Jump up ^ Mega-tsunami : Wave of Destruction . Transcript . BBC Two television programme , first broadcast 12 October 2000 Jump up ^ Evans , S.G. ; Savigny , K.W. ( 1994 ) . `` Landslides in the Vancouver - Fraser Valley - Whistler region '' ( PDF ) . Geological Survey of Canada . Ministry of Forests , Province of British Columbia . pp. 36 p . Retrieved 2008 - 12 - 28 . ^ Jump up to : Day et al. 1999 ^ Jump up to : Ward & Day 2001 Jump up ^ Bonelli 1950 Jump up ^ Pararas - Carayannis 2002 Jump up ^ As per Bonelli Rubio Jump up ^ Ali Ayres ( 2004 - 10 - 29 ) . `` Tidal wave threat ' over-hyped ' '' . BBC NEWS . Jump up ^ Pararas - Carayannis , George ( 2002 ) . `` Evaluation of the threat of mega tsunami generation from postulated massive slope failures of the island volcanoes on La Palma , Canary Islands , and on the island of Hawaii '' ( PDF ) . Science of Tsunami Hazards. 20 ( 5 ) : 251 -- 277 . Retrieved 7 September 2014 . Jump up ^ McMurtry , Gary M. ; Fryer , Gerard J. ; Tappin , David R. ; Wilkinson , Ian P. ; Williams , Mark ; Fietzke , Jan ; Garbe - Schoenberg , Dieter ; Watts , Philip ( 1 September 2004 ) . `` Megatsunami deposits on Kohala volcano , Hawaii , from flank collapse of Mauna Loa '' . Geology. 32 ( 9 ) : 741 . Bibcode : 2004Geo ... 32 ... 741M . doi : 10.1130 / G20642. 1 . Jump up ^ McMurtry , Gary M. ; Fryer , Gerard J. ; Tappin , David R. ; Wilkinson , Ian P. ; Williams , Mark ; Fietzke , Jan ; Garbe - Schoenberg , Dieter ; Watts , Philip ( September 1 , 2004 ) . `` A Gigantic Tsunami in the Hawaiian Islands 120,000 Years Ago '' . Geology . SOEST Press Releases . Retrieved 2008 - 12 - 20 . Jump up ^ McMurtry , G.M. ; Tappin , D.R. ; Fryer , G.J. ; Watts , P. ( December 2002 ) . `` Megatsunami Deposits on the Island of Hawaii : Implications for the Origin of Similar Deposits in Hawaii and Confirmation of the ' Giant Wave Hypothesis ' '' . AGU Fall Meeting Abstracts. 51 : 0148 . Bibcode : 2002AGUFMOS51A0148M . Jump up ^ Pararas - Carayannis , George ( 2002 ) . `` Evaluation of the threat of mega tsunami generation from postulated massive slope failures of island volcanoes on La Palma , Canary Islands , and on the island of Hawaii '' . drgeorgepc.com . Retrieved 2008 - 12 - 20 . Jump up ^ Britt , Robert Roy ( 14 December 2004 ) . `` The Megatsunami : Possible Modern Threat '' . LiveScience . Retrieved 2008 - 12 - 20 . Jump up ^ Le Bas , T.P. ( 2007 ) . `` Slope Failures on the Flanks of Southern Cape Verde Islands '' . In Lykousis , Vasilios . Submarine mass movements and their consequences : 3rd international symposium . Springer . ISBN 978 - 1 - 4020 - 6511 - 8 Further reading ( edit ) BBC 2 TV ; 2000 . Transcript `` Mega-tsunami ; Wave of Destruction '' , Horizon . First screened 21.30 hrs , Thursday , 12 October 2000 . Carracedo , J.C. ( 1994 ) . `` The Canary Islands : an example of structural control on the growth of large oceanic - island volcanoes '' . J. Volcanol . Geotherm . Res. 60 ( 3 -- 4 ) : 225 -- 241 . Bibcode : 1994JVGR ... 60 ... 225C . doi : 10.1016 / 0377 - 0273 ( 94 ) 90053 - 1 . Carracedo , J.C. ( 1996 ) . `` A simple model for the genesis of large gravitational landslide hazards in the Canary Islands '' . In McGuire , W ; Jones ; Neuberg , J.P. Volcano Instability on the Earth and Other Planets . Special Publication. 110 . London : Geological Society . pp. 125 -- 135 . Carracedo , J.C. ( 1999 ) . `` Growth , Structure , Instability and Collapse of Canarian Volcanoes and Comparisons with Hawaiian Volcanoes '' . J. Volcanol . Geotherm . Res. 94 : 1 -- 19 . Bibcode : 1999JVGR ... 94 ... 1C . doi : 10.1016 / S0377 - 0273 ( 99 ) 00095 - 5 . Day , S.J. ; Carracedo , J.C. ; Guillou , H. ; Gravestock , P. ( 1999 ) . `` Recent structural evolution of the Cumbre Vieja volcano , La Palma , Canary Islands : volcanic rift zone re-configuration as a precursor to flank instability '' ( PDF ) . J. Volcanol . Geotherm . Res. 94 : 135 -- 167 . Bibcode : 1999JVGR ... 94 ... 135D . doi : 10.1016 / S0377 - 0273 ( 99 ) 00101 - 8 . Moore , J.G. ( 1964 ) . `` Giant Submarine Landslides on the Hawaiian Ridge '' . US Geologic Survey : D95 -- 8 . Professional Paper 501 - D . Pararas - Carayannis , G. ( 2002 ) . `` Evaluation of the Threat of Mega Tsunami Generation from Postulated Massive Slope Failure of Island Stratovolcanoes on La Palma , Canary Islands , and on The Island of Hawaii , George '' . Science of Tsunami Hazards. 20 ( 5 ) : 251 -- 277 . Pinter , N. ; Ishman , S.E. ( 2008 ) . `` Impacts , mega-tsunami , and other extraordinary claims '' ( PDF ) . GSA Today . 18 ( 1 ) : 37 -- 38 . doi : 10.1130 / GSAT01801GW. 1 . Rihm , R ; Krastel , S. & CD109 Shipboard Scientific Party ; 1998 . Volcanoes and landslides in the Canaries . National Environment Research Council News . Summer , 16 -- 17 . Siebert , L. ( 1984 ) . `` Large volcanic debris avalanches : characteristics of source areas , deposits and associated eruptions '' . J. Volcanol . Geotherm . Res. 22 ( 3 -- 4 ) : 163 -- 197 . Bibcode : 1984JVGR ... 22 ... 163S . doi : 10.1016 / 0377 - 0273 ( 84 ) 90002 - 7 . Vallely , G.A. ( 2005 ) . `` Volcanic edifice instability and tsunami generation : Montaña Teide , Tenerife , Canary Islands ( Spain ) '' . Journal of the Open University Geological Society . 26 ( 1 ) : 53 -- 64 . Voight , B. ; Janda , R. ; Glicken , H. ; Douglas , P.M. ( 1983 ) . `` Nature and mechanics of the Mount St Helens rockslide - avalanche of 18 May 190 '' . Géotechnique. 33 ( 10 ) : 243 -- 273 . doi : 10.1680 / geot. 1983.33. 3.243 . Ward , S.N. ; Day , S. ( 2001 ) . `` Cumbre Vieja Volcano -- Potential collapse and tsunami at La Palma , Canary Islands '' ( PDF ) . Geophysical Research Letters. 28 ( 17 ) : 3397 -- 3400 . Bibcode : 2001GeoRL ... 28.3397 W . doi : 10.1029 / 2001GL013110 . Sandom , J.G. , 2010 , The Wave -- A John Decker Thriller , Cornucopia Press , 2010 . A thriller in which a megatsunami is intentionally created when a terrorist detonates a nuclear bomb on La Palma in the Canary Islands . Bonelli Rubio , J.M. , 1950 . Contribucion al estudio de la erupcion del Nambroque o San Juan . Madrid : Inst . Geografico y Catastral , 25 pp . Ortiz , J.R. , Bonelli Rubio , J.M. , 1951 . La erupción del Nambroque ( junio - agosto de 1949 ) . Madrid : Talleres del Instituto Geográfico y Catastral , 100 p. , 1h . pleg. ; 23 cm External links ( edit ) Mega Tsunami : history , causes , effects World 's Biggest Tsunami : The largest recorded tsunami with a wave 1720 feet tall in Lituya Bay , Alaska . Benfield Hazard Research Centre BBC -- Mega-tsunami : Wave of Destruction BBC Two program broadcast 12 October 2000 La Palma threat `` over-hyped '' , BBC News , 29 October 2004 Mega-hyped Tsunami story A detailed of analysis demolishing the La Palma Tsunami speculation . 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where did the world's largest recorded wave occur
A megatsunami is a very large wave created by a large , sudden displacement of material into a body of water . Megatsunamis have quite different features from other , more usual types of tsunamis . Most tsunamis are caused by underwater tectonic activity ( movement of the earth 's plates ) and therefore occur along plate boundaries and as a result of earthquake and rise or fall in the sea floor , causing water to be displaced . Ordinary tsunamis have shallow waves out at sea , and the water piles up to a wave height of up to about 10 metres ( 33 feet ) as the sea floor becomes shallow near land . By contrast , megatsunamis occur when a very large amount of material suddenly falls into water or anywhere near water ( such as via a meteor impact ) , or are caused by volcanic activity . They can have extremely high initial wave heights of hundreds and possibly thousands of metres , far beyond any ordinary tsunami , as the water is `` splashed '' upwards and outwards by the impact or displacement . As a result , two heights are sometimes quoted for megatsunamis -- the height of the wave itself ( in water ) , and the height to which it surges when it reaches land , which depending upon the locale , can be several times larger . Modern megatsunamis include the one associated with the 1883 eruption of Krakatoa ( volcanic eruption ) , the 1958 Lituya Bay megatsunami ( landslide into a bay ) , and the wave resulting from the Vajont Dam landslide ( caused by human activity destabilizing sides of valley ) . Prehistoric examples include the Storegga Slide ( landslide ) , and the Chicxulub , Chesapeake Bay and Eltanin meteor impacts . A megatsunami is a tsunami -- a large wave due to displacement of a body of water -- with an initial wave amplitude ( height ) measured in several tens , hundreds , or possibly thousands of metres . Normal tsunamis generated at sea result from movement of the sea floor . They have a small wave height offshore , are very long ( often hundreds of kilometres ) , and generally pass unnoticed at sea , forming only a slight swell usually of the order of 30 cm ( 12 in ) above the normal sea surface . When they reach land , the wave height increases dramatically as the base of the wave pushes the water column above it upwards . By contrast , megatsunamis are caused by giant landslides and other impact events . This could also refer to a meteorite hitting an ocean . Underwater earthquakes or volcanic eruptions do not normally generate such large tsunamis , but landslides next to bodies of water resulting from earthquakes can , since they cause a large amount of displacement . If the landslide or impact occurs in a limited body of water , as happened at the Vajont Dam ( 1963 ) and Lituya Bay ( 1958 ) then the water may be unable to disperse and one or more exceedingly large waves may result . A way to visualize the difference , is that an ordinary tsunami is caused by sea floor changes , somewhat like pushing up on the floor of a large tub of water to the point it overflows , and causing a surge of water to `` run off '' at the sides . In this analogy , a megatsunami would be more similar to dropping a large rock from a considerable height into the tub , at one end , causing water to splash up and out , and overflow at the other end . Two heights are sometimes quoted for megatsunamis -- the height of the wave itself ( in water ) , and the height to which it surges when it reaches land , which depending upon the locale , can be several times larger . Geologists searching for oil in Alaska in 1953 observed that in Lituya Bay , mature tree growth did not extend to the shoreline as it did in many other bays in the region . Rather , there was a band of younger trees closer to the shore . Forestry workers , glaciologists , and geographers call the boundary between these bands a trim line . Trees just above the trim line showed severe scarring on their seaward side , whilst those from below the trim line did not . The scientists hypothesized that there had been an unusually large wave or waves in the deep inlet . Because this is a recently deglaciated fjord with steep slopes and crossed by a major fault , one possibility was a landslide - generated tsunami . On 9 July 1958 , a 7.8 M strike - slip earthquake in southeast Alaska caused 90 million tonnes of rock and ice to drop into the deep water at the head of Lituya Bay . The block fell almost vertically and hit the water with sufficient force to create a wave that surged up the opposite side of the head of the bay to a height of 1720 feet ( 524 m ) , and was still many tens of metres high further down the bay , when it carried eyewitnesses Howard Ulrich and his son Howard Jr. over the trees in their fishing boat . They were washed back into the bay and both survived . The mechanism giving rise to megatsunamis was analysed for the Lituya Bay event in a study presented at the Tsunami Society in 1999 ; this model was considerably developed and modified by a second study in 2010 . Although the earthquake which caused the megatsunami was considered very energetic , and involving strong ground movements , several possible mechanisms were not likely or able to have caused the resulting megatsunami . Neither water drainage from a lake , nor landslide , nor the force of the earthquake itself led to the megatsunami , although all of these may have contributed . Instead , the megatsunami was caused by a massive and sudden impulsive impact when about 40 million cubic yards of rock several hundred metres above the bay was fractured from the side of the bay , by the earthquake , and fell `` practically as a monolithic unit '' down the almost vertical slope and into the bay . The rockfall also caused air to be `` dragged along '' due to viscosity effects , which added to the volume of displacement , and further impacted the sediment on the floor of the bay , creating a large crater . The study concluded that : `` The giant wave runup of 1,720 feet ( 524 m . ) at the head of the Bay and the subsequent huge wave along the main body of Lituya Bay which occurred on July 9 , 1958 , were caused primarily by an enormous subaerial rockfall into Gilbert Inlet at the head of Lituya Bay , triggered by dynamic earthquake ground motions along the Fairweather Fault . `` The giant wave runup of 1,720 feet ( 524 m . ) at the head of the Bay and the subsequent huge wave along the main body of Lituya Bay which occurred on July 9 , 1958 , were caused primarily by an enormous subaerial rockfall into Gilbert Inlet at the head of Lituya Bay , triggered by dynamic earthquake ground motions along the Fairweather Fault . The large mass of rock , acted as a monolith ( thus resembling high - angle asteroid impact ) , struck with great force the sediments at bottom of Gilbert Inlet at the head of the bay . The impact created a large crater and displaced and folded recent and Tertiary deposits and sedimentary layers to an unknown depth . The displaced water and the displacement and folding of the sediments broke and uplifted 1,300 feet of ice along the entire front of the Lituya Glacier at the north end of Gilbert Inlet . Also , the impact and the sediment displacement by the rockfall resulted in an air bubble and in water splashing action that reached the 1,720 foot ( 524 m . ) elevation on the other side of the head of Gilbert Inlet . The same rockfall impact , in combination with the strong ground movements , the net vertical crustal uplift of about 3.5 feet , and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated , generated the giant solitary gravity wave which swept the main body of the bay . The large mass of rock , acted as a monolith ( thus resembling high - angle asteroid impact ) , struck with great force the sediments at bottom of Gilbert Inlet at the head of the bay . The impact created a large crater and displaced and folded recent and Tertiary deposits and sedimentary layers to an unknown depth . The displaced water and the displacement and folding of the sediments broke and uplifted 1,300 feet of ice along the entire front of the Lituya Glacier at the north end of Gilbert Inlet . Also , the impact and the sediment displacement by the rockfall resulted in an air bubble and in water splashing action that reached the 1,720 foot ( 524 m . ) elevation on the other side of the head of Gilbert Inlet . The same rockfall impact , in combination with the strong ground movements , the net vertical crustal uplift of about 3.5 feet , and an overall tilting seaward of the entire crustal block on which Lituya Bay was situated , generated the giant solitary gravity wave which swept the main body of the bay . This was the most likely scenario of the event -- the '' PC model '' that was adopted for subsequent mathematical modeling studies with source dimensions and parameters provided as input . Subsequent mathematical modeling at the Los Alamos National Laboratory ( Mader , 1999 , Mader & Gittings , 2002 ) supported the proposed mechanism -- as there was indeed sufficient volume of water and an adequately deep layer of sediments in the Lituya Bay inlet to account for the giant wave runup and the subsequent inundation . The modeling reproduced the documented physical observations of runup . '' This was the most likely scenario of the event -- the '' PC model '' that was adopted for subsequent mathematical modeling studies with source dimensions and parameters provided as input . Subsequent mathematical modeling at the Los Alamos National Laboratory ( Mader , 1999 , Mader & Gittings , 2002 ) supported the proposed mechanism -- as there was indeed sufficient volume of water and an adequately deep layer of sediments in the Lituya Bay inlet to account for the giant wave runup and the subsequent inundation . The modeling reproduced the documented physical observations of runup . '' A 2010 model examined the amount of infill on the floor of the bay , which was many times larger than that of the rockfall alone , and also the energy and height of the waves , and the accounts given by eyewitnesses , concluded that there had been a `` dual slide '' involving a rockfall , which also triggered a release of 5 to 10 times its volume of sediment trapped by the adjacent Lituya Glacier , as an almost immediate and many times larger second slide , a ratio comparable with other events where this `` dual slide '' effect is known to have happened . The asteroid linked to the extinction of dinosaurs , which created the Chicxulub crater in Yucatán approximately 66 million years ago , would have caused an over 100 metres ( 330 ft ) tall megatsunami . The height of the tsunami was limited due to relatively shallow sea in the area of the impact ; in deep sea it would be 4.6 kilometres ( 2.9 mi ) tall . A series of megatsunamis were generated by the bolide impact that created the Chesapeake Bay impact crater , about 35.5 million years ago . During the Messinian the coasts of northern Chile were likely struck by various megatsunamis . A megatsunami affected the coast of south -- central Chile in the Pliocene as evidenced by the sedimentary record of Ranquil Formation . The Eltanin impact in the southeast Pacific Ocean 2.5 million years ago caused a megatsunami that was over 200 m ( 660 ft ) high in southern Chile and the Antarctic Peninsula ; the wave swept across much of the Pacific Ocean . The northern half of the East Molokai Volcano suffered a catastrophic collapse and likely megatsunami about 1.5 million years ago and now lies as a debris field scattered northward across the ocean bottom , while what remains on the island are the highest sea cliffs in the world . The existence of large scattered boulders in only one of the four marine terraces of Herradura Bay south of the Chilean city of Coquimbo has been interpreted by Roland Paskoff as the result of a mega-tsunami that occurred in the Middle Pleistocene . A massive collapse of the western edge of the Lake Tahoe basin , which formed McKinney Bay around 50,000 years ago , is thought to have generated a tsunami / seiche wave with a height approaching 330 ft ( 100 m ) . In the North Sea , the Storegga Slide caused a megatsunami approximately 8,200 years ago . It is estimated to have completely flooded the remainder of Doggerland . Approximately 8,000 years ago , a massive volcanic landslide off Mt . Etna , Sicily caused a megatsunami which devastated the eastern Mediterranean coastline on three continents . Wave heights on the coast of Calabria are estimated to have reached a maximum of 40m . Approximately 4,000 years ago , a landslide on Réunion island , to the east of Madagascar , may have caused a megatsunami . The asteroid linked to the extinction of dinosaurs , which created the Chicxulub crater in Yucatán approximately 66 million years ago , would have caused an over 100 metres ( 330 ft ) tall megatsunami . The height of the tsunami was limited due to relatively shallow sea in the area of the impact ; in deep sea it would be 4.6 kilometres ( 2.9 mi ) tall . A series of megatsunamis were generated by the bolide impact that created the Chesapeake Bay impact crater , about 35.5 million years ago . During the Messinian the coasts of northern Chile were likely struck by various megatsunamis . A megatsunami affected the coast of south -- central Chile in the Pliocene as evidenced by the sedimentary record of Ranquil Formation . The Eltanin impact in the southeast Pacific Ocean 2.5 million years ago caused a megatsunami that was over 200 m ( 660 ft ) high in southern Chile and the Antarctic Peninsula ; the wave swept across much of the Pacific Ocean . The northern half of the East Molokai Volcano suffered a catastrophic collapse and likely megatsunami about 1.5 million years ago and now lies as a debris field scattered northward across the ocean bottom , while what remains on the island are the highest sea cliffs in the world . The existence of large scattered boulders in only one of the four marine terraces of Herradura Bay south of the Chilean city of Coquimbo has been interpreted by Roland Paskoff as the result of a mega-tsunami that occurred in the Middle Pleistocene . A massive collapse of the western edge of the Lake Tahoe basin , which formed McKinney Bay around 50,000 years ago , is thought to have generated a tsunami / seiche wave with a height approaching 330 ft ( 100 m ) . In the North Sea , the Storegga Slide caused a megatsunami approximately 8,200 years ago . It is estimated to have completely flooded the remainder of Doggerland . Approximately 8,000 years ago , a massive volcanic landslide off Mt . Etna , Sicily caused a megatsunami which devastated the eastern Mediterranean coastline on three continents . Wave heights on the coast of Calabria are estimated to have reached a maximum of 40m . Approximately 4,000 years ago , a landslide on Réunion island , to the east of Madagascar , may have caused a megatsunami . 3,600 years ago , the Thera volcano erupted , the force of the eruption causing megatsunamis which affected the whole Aegean sea and the eastern Mediterranean sea . 3,600 years ago , the Thera volcano erupted , the force of the eruption causing megatsunamis which affected the whole Aegean sea and the eastern Mediterranean sea . In 1792 , Mount Unzen in Japan erupted , causing part of the volcano to collapse into the sea . The landslide caused a megatsunami that reached 100 metres ( 330 ft ) high and killed 15,000 people in the local fishing villages . The eruption of Krakatoa created pyroclastic flows which generated megatsunamis when they hit the waters of the Sunda Strait on 27 August 1883 . The waves reached heights of up to 24 metres ( 79 feet ) along the south coast of Sumatra and up to 42 metres ( 138 feet ) along the west coast of Java . On July 9 , 1958 , a giant landslide at the head of Lituya Bay in Alaska , caused by an earthquake , generated a wave that washed out trees to a maximum altitude of 520 metres ( 1,710 ft ) at the entrance of Gilbert Inlet . The wave surged over the headland , stripping trees and soil down to bedrock , and surged along the fjord which forms Lituya Bay , destroying a fishing boat anchored there and killing two people . Howard Ulrich and his son managed to ride the wave in their boat , and both survived . On October 9 , 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 . On May 18 , 1980 , the upper 460 metres ( 1,509 feet ) of Mount St. Helens collapsed , creating a massive 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 ( 853 feet ) above the pre-eruption water level ( ~ 975 m asl / 3,199 ft ) . 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 . Experts interviewed by the BBC think that a massive landslide on a volcanic ocean island is the most likely future cause of a megatsunami . The size and power of a wave generated by such means could produce devastating effects , travelling across oceans and inundating up to 25 kilometres ( 16 mi ) inland from the coast . Some geologists consider an unstable rock face at Mount Breakenridge , above the north end of the giant fresh - water fjord of Harrison Lake in the Fraser Valley of southwestern British Columbia , Canada , to be unstable enough to collapse into the lake , generating a megatsunami that might destroy the town of Harrison Hot Springs ( located at its south end ) . Geologists Dr. Simon Day and Dr. Steven Neal Ward consider that a megatsunami could be generated during an eruption of Cumbre Vieja on the volcanic ocean island of La Palma , in the Canary Islands , Spain . In 1949 , this volcano erupted at its Duraznero , Hoyo Negro and Llano del Banco vents , and there was an earthquake with an epicentre near the village of Jedey . The next day Juan Bonelli Rubio , a local geologist , visited the summit area and found that a fissure about 2.5 kilometres ( 1.6 mi ) long had opened on the east side of the summit . As a result , the west half of the volcano ( which is the volcanically active arm of a triple - armed rift ) had slipped about 2 metres ( 6.6 ft ) downwards and 1 metre ( 3.3 ft ) westwards towards the Atlantic Ocean , Cumbre Vieja is currently dormant , but will almost certainly erupt again . Day and Ward hypothesize that if such an eruption causes the western flank to fail , a mega-tsunami could be generated . La Palma is currently the most volcanically active island in the Canary Islands Archipelago . It is likely that several eruptions would be required before failure would occur on Cumbre Vieja . However , the western half of the volcano has an approximate volume of 500 cubic kilometres ( 120 cu mi ) and an estimated mass of 1.5 trillion metric tons ( 1.7 × 10 short tons ) . If it were to catastrophically slide into the ocean , it could generate a wave with an initial height of about 1,000 metres ( 3,300 ft ) at the island , and a likely height of around 50 metres ( 164 ft ) at the Caribbean and the Eastern North American seaboard when it runs ashore eight or more hours later . Tens of millions of lives could be lost in the cities and / or towns of St. John 's , Halifax , Boston , New York , Baltimore , Washington , D.C. , Miami , Havana and the rest of the Eastern Coasts of the United States and Canada , as well as many other cities on the Atlantic coast in Europe , South America and Africa . The likelihood of this happening is a matter of vigorous debate . The last eruption on the Cumbre Vieja occurred in 1971 at the Teneguia vent at the southern end of the sub-aerial section without any movement . The section affected by the 1949 eruption is currently stationary and does not appear to have moved since the initial rupture . Geologists and volcanologists are in sharp disagreement about whether an eruption on the Cumbre Vieja would cause a single large gravitational landslide or a series of smaller landslides , or whether a slide is likely at all . There are also questions about the dynamics . Day and Ward have admitted that their original analysis of the danger was based on several worst case assumptions . Sharp cliffs and associated ocean debris at the Kohala Volcano , Lanai and Molokai indicate that landslides from the flank of the Kilauea and Mauna Loa volcanoes in Hawaii may have triggered past megatsunamis , most recently at 120,000 BP . A tsunami event is also possible , with the tsunami potentially reaching up to about 1 kilometre ( 3,300 ft ) in height . According to the documentary National Geographic 's Ultimate Disaster : Tsunami , if a big landslide occurred at Mauna Loa or the Hilina Slump , a 30 - metre ( 98 ft ) tsunami would take only thirty minutes to reach Honolulu , Hawaii . There , hundreds of thousands of people could be killed as the tsunami could level Honolulu and travel 25 kilometres ( 16 mi ) inland . Also , the West Coast of America and the entire Pacific Rim could potentially be affected . Steep cliffs on the Cape Verde Islands have been caused by catastrophic debris avalanches . These have been common on the submerged flanks of ocean island volcanoes and more can be expected in the future .
Lituya Bay in Alaska Lituya Bay in Alaska