Persistent weak layer (slab avalanche)

Persistent weak layers. Film: NVE

This avalanche problem causes the most fatalities. The avalanche can be triggered from a distance and, unlike other avalanche problems, this avalanche problem lasts a very long time (persistent). Mild temperatures over a long period and rain are the only thing that can make this avalanche problem cease. It is very difficult to know where in the terrain the problem is present, since it is not visible on the snow surface.

Persistent weak layers often produce wide avalanches, and they can run a long way. Photo: Varsom