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Avalanche

Avalanche

An avalanche is a rapid downslope movement of some combination of rock , regolith , snow, slush, and ice . The movement can occur by any combination of sliding, falling, and rolling of pieces within the avalanche mass, but is generally very rapid. Avalanche velocities can reach tens to hundreds of kilometers per hour.

The term avalanche is generally associated with snow and ice. In its most general form, however, it can refer to the cascading of sand grains down the leeward face of a dune or the rapid downslope movement of largely disaggregated rock without snow or ice. Rock avalanches, for example, are very rapid and catastrophic mass movements of bedrock that has been broken into innumerable pieces either before or during movement.

Snow avalanches, hereafter referred to simply as avalanches, are classified according to whether they move across existing snow layers (surface avalanche) or the ground (ground avalanche), whether they are dry or wet, whether they move through the air or over ground and snow, and whether they consist of loose snow or intact slabs. Like landslides, avalanches begin when the weight of snow above some potential sliding surface exceeds the shear strength along that surface. In many cases, sliding occurs along a former snow surface that is quickly buried by new snow during a storm. The physics of slip surface formation, however, are more complicated for avalanches than most landslides because the snow and ice in an avalanche prone slope are near their melting points. Thus, phase transitions and metamorphosis of snow and ice crystals can alter the strength of snow and ice slopes in a way that does not occur in soil or rock slopes. Melting can also trigger avalanches. Although it is not proven that loud noises such as shouting can trigger avalanches, the vibrations caused by explosives can do soand explosives are often used to deliberately trigger avalanches under controlled conditions as a safety measure.

The aftermath of an avalanche is an avalanche track or chute, which is commonly marked by bent or broken trees and significant amounts of erosion . The track can be either a channel-like or open feature. The rock and debris carried by an avalanche can be deposited as an avalanche cone when the avalanche comes to rest, and the rock debris deposited at the base of a cliff or other steep slope by an avalanche is known as avalanche talus.

See also Catastrophic mass movements; Freezing and melting; Ice; Landslide; Mass movement; Mass wasting; Phase state changes

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avalanche

av·a·lanche / ˈavəˌlanch/ • n. a mass of snow, ice, and rocks falling rapidly down a mountainside. ∎  a large mass of any material moving rapidly downhill: an avalanche of mud. ∎ fig. a sudden arrival or occurrence of something in overwhelming quantities: we have had an avalanche of applications. ∎  Physics a cumulative process in which a fast-moving ion or electron generates further ions and electrons by collision. • v. [intr.] (of a mass of snow, ice, and rocks) descend rapidly down a mountainside. ∎  [tr.] (usu. be avalanched) engulf or carry off by such a mass of material: the climbers were avalanched down the south face of the mountain. ∎  [intr.] Physics undergo a rapid increase in conductivity due to an avalanche process.

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"avalanche." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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"avalanche." The Oxford Pocket Dictionary of Current English. . Retrieved October 16, 2017 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/avalanche-0

avalanche

avalanche, rapidly descending large mass of snow, ice, soil, rock, or mixtures of these materials, sliding or falling in response to the force of gravity. Avalanches, which are natural forms of erosion and often seasonal, are usually classified by their content such as a debris or snow avalanche. Speeds can reach over 200 mi per hr (300 km per hr). They are triggered by such events as earthquake tremors, human-made disturbances, or excessive rainfall on high gradient slopes, often where materials are loosely consolidated or weathered. Avalanches of snow result when weak layers within a snowpack fail to support the weight of the snow above it and collapse, causing the overlying snow to break free and flow downhill. Destruction from avalanches results both from the avalanche wind (the air pushed ahead of the mass) and from the actual impact of the avalanche material.

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"avalanche." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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avalanche

avalanche XVIII. — F., alt., by blending with avaler descend, of Alpine F. dial. lavanche, of unkn. orig.

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"avalanche." The Concise Oxford Dictionary of English Etymology. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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avalanche wind

avalanche wind A blast of often very destructive air ahead of a descending avalanche (see mass-wasting).

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"avalanche wind." A Dictionary of Ecology. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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avalanche wind

avalanche wind A blast of often very destructive air ahead of a descending avalanche.

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avalanche

avalanche See MASS-WASTING.

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"avalanche." A Dictionary of Earth Sciences. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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"avalanche." A Dictionary of Earth Sciences. . Retrieved October 16, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/avalanche

avalanche

avalanche See mass-wasting.

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"avalanche." A Dictionary of Ecology. . Encyclopedia.com. 16 Oct. 2017 <http://www.encyclopedia.com>.

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avalanche

avalanche •Romansh •blanch, Blanche, branch, ranch, tranche •avalanche •backbench, bench, blench, clench, Dench, drench, entrench, French, frontbench, quench, stench, tench, trench, wench, wrench •crossbench • workbench •cinch, clinch, finch, flinch, inch, lynch, Minch, pinch, squinch, winch •chaffinch • greenfinch • hawfinch •goldfinch • bullfinch •carte blanche, conch •graunch, haunch, launch, paunch, raunch, staunch •brunch, bunch, crunch, hunch, lunch, munch, punch, scrunch •honeybunch • keypunch

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