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In geomorphology, an outburst flood, which is a type of megaflood, is a high-magnitude, low-frequency catastrophic flood involving the sudden release of water.〔O’Connor, J.E. and Beebee, R.A., 2009, Floods from natural rock-material dams, in: Burr, D., Carling, P., and Baker, V. editors, ''Megafloods on Earth and Mars'': Cambridge University Press.〕〔Goudie, A., 2004, ''Encyclopedia of Geomorphology.'' Routledge. London, England. ISBN 0-415-27298-X〕 During the last deglaciation, numerous glacial lake outburst floods were caused by the collapse of either ice sheets or glaciers that formed the dams of proglacial lakes. Examples of older outburst floods are known from the geological past of the Earth and inferred from geomorphological evidence on Mars. Landslides, lahars, and volcanic dams can also block rivers and create lakes, which trigger such floods when the rock or earthen barrier collapses or is eroded. Lakes also form behind glacial moraines, which can collapse and create outburst floods.〔Burr, D.M., Baker, V.R., Carling, P.A. (Eds), 2009. ''Megaflooding on Earth and Mars''. Cambridge University Press. 319 pp.〕 ==Definition and classification== Megafloods are paleofloods (past floods) that involved rates of water flow larger than those in the historical record. They are studied through the sedimentary deposits and the erosional and constructional landforms that individual megafloods have created. Floods that are known to us through historical descriptions are mostly related to meteorological events, such as heavy rains, rapid melting of snowpacks, or combination of these. In the geological past of the Earth, however, geological research has shown that much larger events have occurred.〔 In the case of outburst floods, such floods are typically linked to the collapse of the barrier forming a lake. They fall in the following classification according to the mechanism responsible: *Collapse of glacier dams that impound proglacial lakes (Missoula Floods). *Rapid erosion, melting of ice sheets (jökulhlaups). *Collapse of earthen barriers (landslides or glacial moraines). *Collapse of volcanic dams created by lava flows, lahars, or pyroclastic flows. *Overtopping of earthen or rock barriers * *Lake overtopping (e.g., Lake Bonneville). * *Ocean spilling over a dividing ridge into a landlocked basin (e.g., Zanclean flood, Black Sea flood).〔 A smaller scale example would be the Pantai Remis landslide. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Outburst flood」の詳細全文を読む スポンサード リンク
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