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Show 2 The lee slopes on the Bridger Range average about 35° in inclination. On such slopes, maximum vertical thicknesses of cornices in late winter measure about 10 m. These cornices correspondingly extend upward and outward from the ridgeline as much as 15 m. ( Fig. 3a). If the slopes are steeper than 35 , the horizontal component of development is limited because there is less support along the lee slope line. On 35° lee slopes, measurements made April 2, 1967, indicate that approximately $ k acre feet ( 67,688 m3) 0f water was contained within the cornice masses along the 2.5 km crestline above the Maynard Creek watershed ( Fig. 6). This amounted to about one percent of the total equivalent water estimated to have been stored in the watershed at that time. CORNICE MECHANICS Wedge and Sheet Cornice Growth. Several processes may contribute to cornice growth. The most common type of growth is caused by the downwind accretion of snow particles in progressive outward and upward extending layers. The process forms a wedge shaped"! mass along the leading edge. As a variation to the wedge type growth, under conditions of particularly effective grain to grain adhesion and copious supply of stellar flakes, a horizontal sheet of snow only a few cm. thick may extend as much as 10 cm. into space ( Fig. 2C). These sheets or wedges may eventually collapse or sluff off their own weight, may stiffen to form the base on which succeeding layers build, or may curl downward plastically under the influence of gravity. In the wedge type, the accretion face ( Fig. 1) has an under-slope that slants inward toward the main cornice mass at an initial angle of about 55°. When the wedge is deformed, as it usually is, the angle of the accretion face changes, of course. |