The eruption of Mount St. Helens on May 18, 1980, was one of the most significant volcanic events in U.S. history. A massive landslide triggered the eruption, followed by a powerful blast that devastated over 230 square miles of forest. The eruption released ash that spread across several states and caused 57 deaths. It reduced the volcano’s summit by about 1,300 feet, leaving a massive crater and reshaping the surrounding landscape. | History In Pictures