Science
How does an avalanche happen?
An avalanche works when a mass of snow on a slope suddenly breaks loose and slides downhill, often picking up speed and more snow as it goes. It happens when the weight of the snow overcomes the friction holding it in place.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how an avalanche works.
Step by step
- 1Snow builds up in layers on a steep slope.
- 2A weak layer can give way under the weight above.
- 3Gravity overcomes friction and the slab slides loose.
- 4It accelerates, often gathering more snow on the way down.
- 5Triggers include new snowfall, warming, or a passing skier.
Frequently asked questions
- What triggers an avalanche?
- A weak snow layer failing under the weight above — set off by fresh snow, warming, wind-loading, or the weight of a person.
- Why are some slopes more dangerous?
- Steep slopes (around 30–45°) let gravity overcome friction most easily, making them the most avalanche-prone.
- How do people survive avalanches?
- Quick rescue is key; beacons, airbags, and probes help locate and free buried victims before they run out of air.