Avalanches can be anything falling down the side of a mountain. Snow avalanches can be dangerous because of the power of the snow falling. They can happen at almost any snow covered mountain at any time. In the United States and Canada, avalanches happen in the Pacific Mountains and the Rockies. In other continents, they happen in the Himalayas, the Andes, the Alps, and many different places. Countries that are crossed by snowy mountain ranges should be concerned about avalanches. Every year, over one million avalanches happen. Over 100,000 occur in North America.They mostly happen where there are few trees.
Avalanches occur when snow falls pile snow on top of each other. Then loud noises or movement trigger the avalanche. The time they are most likely to happen is after a fresh snowfall. The ski patrol use large guns to shoot explosives at the mountains. They do this to cause avalanches, when no one else is around, so people can ski down the mountain without worrying about being buried by the dangerous avalanches. In many avalanches, only the top layer of snow moves; when this happens it is called sloughs. They are the least dangerous avalanches, because less snow is falling down.
How people can control avalanches
People can control avalanches by planting trees in the starting zones of the avalanches, the areas were avalanches start. Other people put large snow fences in the starting zones. Both of these ways keep the snow in place. People who live or work near an avalanche path sometimes build walls of rock, earth, or concrete into the run out zone of the avalanche. Just remember, avalanches can happen at any time.
