Avalanche Triggers

Natural avalanches are initiated or triggered by something in nature, such as new snow overloading an existing snowpack, a cornice breaking off, snowmelt, a rockfall, or even an earthquake.

Photograph of a large cornice formed by prevailing winds over a ridgetop, Alaska

In contrast, artificial avalanches are triggered by people and wildlife. Avalanche hazard reduction personnel intentionally trigger avalanches using explosives in order to keep roads, railway corridors, and ski areas safe for use.

Photograph of an avalanche crew firing a howitzer as an avalanche control method on Sylvan Pass in Yellowstone National Park

Natural and artificial avalanches can occur at any time.

  • Direct-action avalanches occur during a storm or just after it’s ended
  • Delayed-action avalanches occur more than 24 hours after a storm has stopped
Recall the avalanche on Glory Bowl. It was triggered and was a avalanche.
Artifically and direct-action

This was an artificially triggered avalanche since it was set off by the snowboarder. It occurred within 24 hours of a snowstorm, making it a direct-action avalanche.