Avalanches are like land slides, but with snow.  It is a skiers/snowboarders worst nightmare.  They are caused by noise or by a form of ice on the bottom and a new layer of snow on the top.  When a skier/snowboarder goes over it and causes an avalanche.  Another way is by simply blasting it to cause an avalanche. It helps it by not causing a skier/snowboarder to die in an avalanche.