Who causes avalanches?
Photo: Bruce Tremper What is an avalanche? There are a couple of basic kinds, loose snow and slab, but slab avalanches are the true danger. Think of the snow pack as a series of layers, akin to a stack of pancakes. The earth would be the plate supporting the stack. The first storm of the season deposits a couple of feet of snow, your first pancake. It sits a few days, but then another storm comes along and deposits the next layer of snow, your second pancake, and so on for the rest of the season until you end up with a large stack. If you were to tilt your plate of pancakes, eventually some of them would naturally slide off due to gravity. Some would slide sooner than others depending on how much friction there were between the individual pancakes. Slopes steep enough will exhibit the same behavior; that is, gravity will cause some of the snow layers to shear and slide depending again on the friction (the bond, in the case of snow) between the individual layers. When a layer of snow sl
