On May 18, 1980 a magnitude 5.1 earthquake triggered the most destructive volcanic eruption in recorded U.S. history. Mt. St. Helens in Washington state exploded violently.

1300 feet (400 meters) of the peak collapsed or blew outwards. As a result, 24 square miles (62 square kilometers) of valley was filled by a debris avalanche. 57 people were killed.

     

           Above image taken by Austin Post, all are courtesy of USGS.