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Old snow: Wet old-snow avalanches usually fall because the snow has become so heavy from water that its weight cannot be held by internal cohesion or its bond to underlying snow or ground. This type of avalanche usually falls in the same tracks each year. Abnormal avalanches may occur in years of heavy snowfall or warm spring. The snow in such an avalanche is wet and slushy, and flows very much like mud. Wind-slab avalanches.—Wind-slab avalanches may occur at any time after formation of a wind slab, until the slab has settled and is once more bonded to the underlying snow. The ease with which a slab slides after being broken depends on the character of the underlying snow and the gradient of the slope, and the ease with which it breaks depends on the toughness of the slab, on its thickness, on its size, and on the depth of the space between the slab and the underlying snow. The thickness of slabs varies from a few inches to two or three feet. It should |
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