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Ground surface.—Inequalities in the ground surface, such as rocks, mounds, or terraces, tend to give a firm anchorage to the lowest snow layer, and whenever numerous firmly placed rocks are protruding above the snow, the avalanche danger will be negligible. Rounded, downward-sloping ledges give little support to snow, but angular, upward-tilted ledges give considerable support. Grass usually forms a poor bond with the lowest snow layer since the grass bends downhill and is matted into a slippery surface. This is sometimes also true of the more flexible types of brush, but shrubs with fairly rigid |
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