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downhill. A wind slab on a convex slope is more likely to be under some initial internal tension than a wind slab on a concave slope. A slab on a convex slope, therefore, should tend to fracture more readily. Most avalanches fall in chutes or gullies (or couloirs); indeed, in high mountains, these chutes owe their existence primarily to erosion by frequent avalanches. These avalanches are mostly of the flowing type, however, and are frequently started by snow falling off the headwalls. Obviously, then, when a skier crosses an avalanche chute, it is not enough that he merely know the character of the snow in the chute. The imminent danger is in the slopes high above, the structure of which is usually entirely different from slopes in the chute. |
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