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Avalanche

Avalanche, the slipping of an accumulation of snow or ice down a steep declivity in Alpine regions. Avalanches are sometimes classified as ice, snowy and drift or dust avalanches. Ice avalanches occur in summer, being detached from glaciers; snowy avalanches occur in spring, sliding down habitual channels, which they polish; and drift avalanches occur in winter after heavy falls of snow, consisting of loose snow, accompanied in its fall by a rush of wind. Avalanches, especially the two latter kinds, often prove very destructive, so that the growth of forests is encouraged or masonry is erected to ward them off; but their most important action is indirect, in blocking the course of streams, so as to form temporary lakes and cause floods.