Sun crust

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Sun crust is a type of snow crust formed by refreezing after surface snow crystals have been melted by the sun.
Sun crust is a type of snow crust formed by refreezing after surface snow crystals have been melted by the sun.

Sun crust is a type of snow crust formed by refreezing after surface snow crystals have been melted by the sun.

This type of crust is composed of individual ice particles such as firn, but the sun's action may also produce a film crust.

A frozen sun crust sometimes forms a hard bed surface for future avalanches to run upon. However, a sun crust typically has a fairly rough texture when compared to the more slippery rain crust, and snow deposited on the crust tends to bond better than you would imagine.

However, a sun crust forms a strong mechanical discontinuity in the snowpack, which tends to concentrate any shear deformation within the snowpack to the layers just above and below the sun crust.

But probably more important, crusts tend to concentrate temperature gradients above and below them and they can grow a thin and almost invisible layer of weak faceted snow.

This probably accounts for most of the avalanches that occur on sun crusts, especially in non-maritime climates. Also, surface hoar that grows on top of a sun crust can be a very nasty weak layer.


[edit] Also See

[edit] Reference

  1. Glossary of Meteorology Sun crest [1]
  2. National Avalanche Center and The Friends of the Utah Avalanche Forecast Center. Sun crest [2]
  3. Glossary of Meteorology Snow Crest [3]



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