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Show structures, but also more substantial buildings. For example, some sturdy concrete foundation pillars were bent ( tilted) 30° by an avalanche of December. 5, 1935, although the slide was already " at the discharge" ( spent). The loose snow ( in the dump) penetrates the smallest crevices, completely taking up all available space. A " slab snow" avalanche, a variant of the pulverized snow type, is one in which firm drifted snow that has hardened since the last windstorm descends in combination with loose drifted snow. The avalanche snow is often from a lower layer of hardened drifted snow laid down much earlier. Ragged, angular fragments or " slabs" are found in considerable number in the dump snow. The dump is a flattened elongated cone, sometimes showing transverse waves. " Slab snow" avalanches occur mostly in cirques and shallow craters. Typical pulverized snow avalanches and " slab snow" slides may be observed at adjoining sites on the same day. B. Avalanches Caused by Decrease in Snow Stability Because of Recrystallization. 3) Crumbled snow: The decrease in cohesive force in loose snow following recrystallization may continue to the point where the upper snow layers begin to crumble. The type of rupture for such avalanches has not yet been clearly determined. The dump is a flat or humpy elongated cone. The avalanche snow is a loose, fast- frozen mass of granular ice. We observed that crumbled snow avalanches come only from deep gullies after prolonged periods ( 20- 30 days) of relatively still weather. Since precipitation and windstorms are constantly adding fresh snow to the snowcover, these avalanches are infrequent in the " pure" type. Granular snow will be mixed with fresh snow in the dump. By the same token, an addition of granular snow is often found in the dumps of pulverized snow avalanches. During our entire period of observation, only six avalanches of this type occurred. The volume of the largest was 500 m3. The idea that avalanches can be generated by the crumbling of snow following recrystallization was prompted by our own observations. Confirmation of this hypotheses was found in avalanche reports for the first year of observation. Here, an avalanche deposit consisting of granular ice was reported for December 5, 1936. Later on, in January, 1938, five more such avalanches were observed and reported on Mount Ukspor. Fine granular snow is as capable of crumbling as granular snow. The dumps left by avalanches of fine granular snow, however, are difficult to distinguish from those of pulverized snow. Mixed during avalanche movement, fine granular snow binds quickly and the resultant hardened snow mass is very much like the snow in the dump of a pulverized snow avalanche, especially if it has an addition of fresh snow. A more certain indication of the difference is the presence on the cone- shaped dump of " shoulders" or wave ridges, looking as though formed by the loosening up of distinct parts of the snow. Where the avalanche is observed right after its occurrence, loose fine granular snow can be observed in the tail ( of the deposit). Paulke notes that in the Alps avalanches occur several days or as much as two weeks after a snowfall rather than right after this addition to the snowcover. Evidently the cases he cites are those of avalanches - 47- |