5.1.6 Snow deformation

Many people think that snowpack behaves as a solid mass, unable to stretch, compress, or bend. In fact, snow is a viscoelastic material, meaning that an entire snowpack or particular layer can shear and stretch. Understanding this is important when assessing the stability of a snowpack.

A layer of snow has slid off a greenhouse window and deformed

Snow layers can move in several ways:

  • By gliding, where the entire snowpack detaches at the bed (underlying surface) and moves slowly down the slope; the same process occurs with avalanches but at a much faster pace
  • By creep, the slow, differential movement of a slab down the slope, with the upper portion traveling faster than the lower portion; this process occurs slowly, but can produce tension in the snowpack that can eventually produce a slide