How Do Avalanches Start? An avalanche occurs when a layer of snow collapses and slides downhill. Avalanches are caused by four factors: a steep slope, snow cover, a weak layer in the snow cover and a trigger. Roads and railway tracks may be rerouted to reduce risks. Safe avalanches may be triggered in dangerous snow
How Fast Do Avalanches Travel? The moving mass picks up even more snow as it rushes downhill. A large, fully developed avalanche can weigh as much as a million tons. It can travel faster than 320 kilometers per hour (200 miles per hour). Avalanches occur as layers in a snowpack slide off. Can you outrun
How Often Do Avalanches Occur? The thickness and speed of slab avalanches make them a threat to skiers, snowboarders, mountaineers, and hikers. In the mountains of the western United States, there are about 100,000 avalanches each year. Avalanches kill more than 150 people worldwide each year. Most are snowmobilers, skiers, and snowboarders. What are the