An avalanche occurs when a massive layer of snow collapses and starts to slide downhill. These giant clouds of snow can rush towards you as fast as 90 km/h or 55 mi/h. There are more than 150 people killed by an avalanche every year. After being buried in an avalanche for an hour, the only one in three victims is found alive. The majority of avalanche related deaths are suffocation, hypothermia, and injuries sustained during the disaster.