A Melt-Freeze Crust or Rain Crust is a discontinuity between
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
layers which can lead to
avalanche
An avalanche is a rapid flow of snow down a slope, such as a hill or mountain.
Avalanches can be set off spontaneously, by such factors as increased precipitation or snowpack weakening, or by external means such as humans, animals, and eart ...
s.
The layer can be created in two ways:
*A temperature high enough to allow surface snow to melt, creating a layer of melt water which may later re-freeze.
*Rain falling and freezing on the surface of existing snow, also creating a frozen layer.
This layer is brittle, smooth and slippery, and does not bond with snow layers above it, allowing the overlying slab of snow to move down the mountain under
gravity
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
when disturbed or if the accumulated snowfall exceeds a critical mass. The initial slab may be as large as 10,000m² and 10 metres thick.
References
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Snow