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Show Heaps, ridges ( waves) and dunes of driven snow present their more gentle slope to the wind; with low- relief features of old " eroded" snow residue - steps, old tracks, etc. -, the opposite is true. Moderate and strong winds form cornices of driven snow over the edges ( brinks) of abruptly sloped hills which lie in the wind's path. The forward edges of these snow cornices projecting over precipices gradually sag. Later storms bring new layers of snow, bringing the thickness of the cornice to several meters. When the relief is right, and the growth of the snow layer at the edge of the drop is rapid, later snow layers do not pile up immediately over the old cornices, but accumulate above, forming gaps that describe a curve as the cornice droops. Usually, the density of cornice snow is 0.30 or more. On slopes under cornices are non- turbulent zones where these same wind- driven storms form numerous pillows of soft snow. Here in these still zones the snow accumulates under undisturbed conditions and is more or less homogeneous. Layers cannot always be distinguished even in snow pillows 2 m in thickness. Wind action gradually wears away these snow pillows, and to some extent the cornices, furnishing the material for the clouds of snow dust which upslope winds carry to higher ridges to sweep up into vertical columns - " snow ghosts". These erect snow whorls are particularly striking in the setting sun, when the valleys are in darkness and the mountain tops appear wrapped in a fiery red glow. On narrow, steep ridges, the wind, blowing alternately from different directions, will sweep up ragged, pointed crests of considerable size. Along gashes ( cuts), such crests take the form of triangular cones, pointed upward. In February, 1934, a snow crest 3- 4 m high was observed along a fault saddle on Mount Yukspor, connecting the main massif with a plateau to the west. What were perhaps its different phases at different places were observed as it advanced over the narrow ridge. Driven Snow " Driven ( swept) snow" is the term we will apply to snow deposited by wind storms. Such snow may be loose ( friable) or hard ( compact). A layer of loose driven snow is not strong and will not support a man. It can be broken into fragments with ragged edges or into plates with rough surfaces; each layer separates easily from the one below it. Such a snow layer is formed during mild storms, has a density of 0.08 - 0.25, and is broken up and transferred by winds of 9- 10 m/ sec. A layer of hard driven snow consists of finely ground crystals transported by the wind. Like the loose snow above, hard driven snow can be broken into ragged- edged fragments and plates; it can be separated in layers even when deposited during a single blow, provided the wind is unsteady and veering. Such a layer is strong; it is not always possible to work it with a metal shovel, and the metal tips of alpenstocks scarcely leave a mark on the denser surfaces. Hill slopes open to the wind are often covered with this type of snow. A layer of this snow is formed by " ground blows" or other strong winds, has a density of 0.25 - 0.50, or even 0.55, and is broken up only by strong winds, as when a " ground blow" scours it off. - 6- |