November 21, 2014
Winter 2013 - 2014

Skiers, Snowboarders, Snowshoers

The following three factors MUST be present for an avalanche to occur:

1) Terrain: The slope must be steeper than about 30 degrees and most often steeper than about 35 degrees. Slopes less than about 30 degrees are not steep enough to avalanche.

2) Snowpack: The snow must be unstable. Mountain snowpacks are a series of layers stacked on top of one another.  Some of the layers are hard and strong, some of them are soft and weak.  The snowpack is unstable when a harder stronger layer sets on top of a softer weaker layer and the soft weak layer can barely support the hard strong layer above it.

3) Trigger:  A trigger provides the stress that causes the weak layer to collapse and the snowpack to avalanche. A triggger could be additional weight from more snow or it could be you.

Next Section: Kinds Of Avalanches »