How do avalanches start on steep mountain slopes?
Quick Answer
An avalanche begins when a snow layer loses stability and breaks free, sliding downhill under gravity. Triggers can include new snowfall, warming, wind loading, or a person crossing the slope.
The Full Story
Snow avalanches happen when the forces holding a snowpack together are weaker than gravity pulling it downslope. Layers within the snow can differ in density, temperature, and bonding, creating a weak layer that can fail suddenly. Fresh snow, strong winds, rising temperatures, or vibrations from people or explosions can trigger release. Once moving, the snow can accelerate rapidly and sweep up more snow, ice, and debris. Avalanches are a major hazard in mountain regions such as the Alps, Rockies, and Himalayas.
Key Facts
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