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Avalanche Types Avalanches may be placed in four classifications: those of ice, dry snow, wet snow, and wind slab. Combinations of several types may occur; for example, an ice avalanche may start several layers of snow, both wet and dry, old or new, on their way down a mountainside. Ice avalanches.—In any precipitous region undergoing heavy glaciation, ice avalanches are frequent, and often of tremendous proportions. Hanging glaciers high on a mountainside will move beyond their support and collapse, sweeping everything before them. In the Himalaya, avalanches started in this manner have been known to travel fully a mile across a level valley floor before spending themselves. Where the course of a glacier is less precipitous, a cliff may be entirely covered with ice, being indicated only by the heavily crevassed and chaotic surface of the glacier, known as an icefall. Here the seracs, or pinnacles of ice, often collapse to cause avalanches of large proportions. |
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