Surviving the snow Last winter there was a avalache that Elyse Saugstad a profetional skier was in. She said it felt like she was in a washing machine she was taust all over she could not tell where up from down was but she thinks that a inflatable bag like a air bag is what saved her life. Because three of her friends who were with her died that day when they found them at the bottom of the slope. Karl Birkeland, director of the U.S. forest service avalanche center in Bozeman, montana, says being in a avalanche is like being in a violent river. But one important factor makes it worse. The density of flowing snow is a lot less than the density of water. He says density is a measure of how heavy something is compared with how big it is. People are denser than flowing snow, so they sink The making of an avalanche The most dangerous avalache is called slab avalanches. They happen when the thick block of snow breaks frr from the mountainside. People set off most avalanches. A persons weight alone can make the layer of snow come down and cause a avalanche.