Summary and Conclusion

A number of well-established physical and mechanical laws are often improperly applied to snow, which is a very particular medium regarding compacity, viscosity, friction, rupture, etc. Snow is described as a changeable granular and porous material, and analyzed using a combination of statistical and deterministic approaches, with the help of the theory of dynamical systems. Specific models are developed for slab, superficial, and full-depth avalanches. The series of successive physical mechanisms responsible for slab avalanche triggering is now perfectly known, involving weak layer collapse and expansion, in which possible healing may abort the whole process. Loose snow avalanches are reminiscent of Bak’s sand pile model, and full-depth avalanches are modeled in terms of snow-water percolation. The specific arrest mechanisms are analyzed. The present analysis should help in taking wise decisions in the face of unexpected situations. The future of snow avalanches is explored in the context of present climate warming.