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Avalanches are a mass movement of snow and ice down a hillside,
which take place when certain circumstances of topography and climate
come together. The topographic factors include the steepness of
slope, the slope inclination (the direction it faces), and the type
of its surface.
A second set of circumstances concerns the amount and characteristics
of each layer of snow. Repeated snowfall in a snow season creates
layers of snow on mountain slopes. When layers differ (have discontinuities)
with those above or below them, there may be circumstances promoting
layers to slide along one another. One example is when a heavy layer
falls on top of hardened snow below it. The nature of snow can also
affect the nature of the sliding: when snow is dry or powderlike,
it may contain a large volume of air, and can reach a high speed
when going downslope. When the snow that is sliding is wet, it will
slide as large blocks.
Descriptions for each of the major avalanches shown on the map are found in the document Major
Avalanches. |
