Slab Avalanche Release Dynamics

Tamar Young
Physics 211

Photo: T. Hocken 2002

Every year in Alaska as fall fades into winter recreaters and explorers prepare their equipment for another season of winter fun. High in the hills some something else is being prepared though.  As the snow depth increases from centimeters to meters a deadly crystalline structure is forming.  These “weak layers” that often develop in the snow pack can lay dormant for weeks or even months waiting for something or some one to tip the critical balance between strength and strain in the snow pack. All too often the trigger is a backcountry traveler and year after year the death toll in Alaska rises.
How can a soft fluffy slope of new snow shatter like a pane of glass, and turn in to a river a frozen ice crystals?  Before we can investigate how slab avalanches are triggered we must first gain an understanding of how snow acts as a material and how slab avalanches form.

Snow as a Material

Avalanche Formation

Forces on the Snowpack