France, Austria, Switzerland and Italy are the countries with the largest number of avalanches each year. The United States is the fifth highest country in terms of avalanche danger, most prominently in Colorado, Alaska and Utah.
Avalanches occur in regions that contain mountainous areas and claim over 150 lives each year throughout the world. Ninety percent of avalanches happen on slopes between 30 and 45 degrees, since snow does not generally accumulate on mountains with steeper slopes. Avalanches occur when the pull of gravity is stronger than the strength of the snow. They can be caused by vibrations, loud sounds or changes in temperature.