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A kettle (kettle hole, pothole) is a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters. ==Overview== Kettles are fluvioglacial landforms occurring as the result of blocks of ice calving from the front of a receding glacier and becoming partially to wholly buried by glacial outwash. Glacial outwash is generated when streams of meltwater flow away from the glacier and deposit sediment to form broad outwash plains called sandurs. When the ice blocks melt, kettle holes are left in the sandur. When the development of numerous kettle holes disrupt sandur surfaces, a jumbled array of ridges and mounds form, resembling kame and kettle topography.〔Bennet, M and Glasser, N: ''Glacial Geology:Ice Sheets and Landforms'', page 262. John Wiley and Sons, 1997〕 Kettle holes can also occur in ridge shaped deposits of loose rock fragments called till.〔Tarbuck, E and Lutgens, F: ''Earth'', page 351. Prentice Hall, 2002〕 Kettle holes can form as the result of floods caused by the sudden drainage of an ice-dammed lake. These floods, called jökulhlaups, often rapidly deposit large quantities of sediment onto the sandur surface. The kettle holes are formed by the melting blocks of sediment-rich ice that were transported and consequently buried by the jökulhlaups. It was found in field observations and laboratory simulations done by Maizels in 1992 that ramparts form around the edge of kettle holes generated by jökulhlaups. The development of distinct types of ramparts depends on the concentration of rock fragments contained in the melted ice block and on how deeply the block was buried by sediment.〔Bennett, M and Glasser, N: ''Glacial Geology: Ice Sheets and Landforms'', page 267. John Wiley and Sons, 1997〕 Most kettle holes are less than two kilometres in diameter, although some in the U.S. Midwest exceed ten kilometres. Puslinch Lake in Ontario, Canada, is the largest kettle lake in Canada spanning . Fish Lake in the north-central Cascade Mountains of Washington State, USA, is .〔Schmuck and Peterson, ''2002 Warmwater Fisheries Survey of Fish Lake, Chelan County, Washington'', page 1, State of Washington, 2005〕 The depth of most kettles is less than ten meters.〔Tarbuck, E and Lutgens, F: ''Earth'', page 351. Prentice Hall, 2002〕 In most cases, kettle holes eventually fill with water, sediment, or vegetation. If the kettle is fed by surface or underground rivers or streams, it becomes a kettle lake. If the kettle receives its water from precipitation, the groundwater table, or a combination of the two, it is termed a kettle pond or kettle wetland, if vegetated. Kettle ponds that are not affected by the groundwater table will usually become dry during the warm summer months, in which case they are deemed ephemeral.〔http://www.slackpacker.com/glacial.html〕 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「Kettle (landform)」の詳細全文を読む スポンサード リンク
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