Snow Formation and Avalanches : Page 203

Dry-snow avalanches.—New snow: This is the most frequently encountered avalanche. The primary cause is a loss of internal cohesion soon after a snowfall, owing to evaporation or transformation of the branches of the snow crystals. This eliminates the bond initially provided by the interlacing of these branches, and permits the snow to flow. Avalanches of this type may occur during or soon after a snowfall, wherever the slope is steep enough. If the snow has fallen on a frozen crust, or even on settled snow when the temperature is well below freezing, the likelihood of avalanche is increased since the poor bond may permit slippage as well as flow, and more gradual slopes are apt to avalanche. If the layer of new snow is only a few inches thick, the likelihood and seriousness of an avalanche is slight, but if the fall has been very deep, or has been collected in large drifts, the likelihood of avalanche, and the possible damage from it, is great.