What Are Avalanches

An avalanche is a large mass of snow that suddenly slides down a mountainside. Avalanches happen when snow becomes unstable and breaks loose from the slope. Understanding avalanches is important because they can cause serious damage and harm to people living in or visiting mountain areas.

Several things can trigger, or start, an avalanche. Heavy snowfall adds weight to the snow already on the mountain, making it more likely to slide. Warming temperatures can melt the bottom layer of snow, creating a slippery surface. Strong winds can pile snow unevenly on slopes, creating weak spots. Even loud sounds, like thunder or explosions, can shake the snow enough to start an avalanche. Think of it like stacking blocks—if you add too many or bump the tower, it falls down.

Once an avalanche starts, it picks up speed quickly as it rushes downhill. The moving snow collects more snow along the way, growing larger and heavier. This is similar to rolling a small snowball down a hill and watching it grow bigger. Avalanches can reach speeds of 80 miles per hour and bury everything in their path under many feet of heavy snow.

Avalanches are most dangerous in mountainous areas where people ski, hike, or live in valleys below steep slopes. They can bury roads, destroy buildings, and trap people under snow. Avalanche warnings are alerts that tell people when conditions are dangerous. These warnings help people stay out of risky areas and save lives.

Interesting Fact: The largest avalanche ever recorded happened in 1970 in Peru, when an earthquake triggered a massive snow and ice slide that traveled 11 miles down a mountain!