Mount St. Helens Erupts in Lateral Blast

A magnitude-5.1 earthquake triggered the collapse of Mount St. Helens' north face in Washington state, releasing a lateral blast of superheated gas and rock traveling at speeds exceeding 480 kilometers per hour at temperatures around 350 degrees Celsius. The eruption destroyed approximately 600 square kilometers of forest and flattened an estimated 10 million trees. The debris avalanche was followed by pyroclastic flows and lahars that reshaped river valleys. Fifty-seven people died, including volcanologist David Johnston.