| Crevasse |
Articles about Crevasse |
Information AboutCrevasse |
| CATEGORIES ABOUT CREVASSE | |
| geological hazards | |
| glaciology | |
| mountain and glacial landforms | |
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A crevasse is a crack or fissure in a Glacier or snow field. The cracks are formed due to changes in glacier speed. An acceleration in glacier speed will cause extension and formation of a crevasse. Transverse crevasses are the most common crevasse type, they form in a zone of extension where the glacier is accelerating as it moves downslope and stretch across the glacier. This happens most commonly where slope increases. Marginal crevasses extend diagonally from the edge of the glacier pointing upglacier. These form because glaciers move slower down the sides than in the center because of the friction between the ice and walls of the mountain. These crevasses form due to the increased speed of the glacier near its center compared to the margin. Longitudinal crevasses form parallel to flow in an area where the glacier width is expanding. Crevasses open up with vertical walls. With time in areas of melting the walls can melt out creating seracs, arches etc. A special variant of a crevasse is a Bergschrund which often marks the top border of a glacier and divides the moving glacier from the static ice, frozen to the steep surrounding walls. A bergschrund extends to bedrock. Crevasses in the accumulation zone also expose the stratigraphy of snowpack, each year separated by a dirty-icy horizon. They can be read much like tree rings. In the picture at right individual storm layers are even visible on the crevasse wall. At the surface a crevasse can be covered by the most recent year's snow, creating a snow bridge that is hard to detect. Falling into a hidden crevasse (for example, one hidden by a layer of blown snow) is a mountaineer's worst nightmare. Falling into a visible crevasse is usually the result of an error in judgement. Anyone planning on walking on glaciers should be trained in Crevasse Rescue . REFERENCE '''', 5th edition. ISBN 0-89886-309-0 |
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