Introduction to Mount St. Helens
July 22,1980 eruption of Mount St. Helens. Taken by Mike Doukas, United States Geological Survey
The May 18, 1980 eruption of Mount St. Helens–a stratovolcano located in Washington state–was the only major volcanic eruption to occur in the contiguous United States since 1915. At 8:32 am, PDT, an earthquake caused the mountain’s north flank, already weakened by months of small earthquakes and eruptions, to break away, releasing a violent conglomeration of scalding ash, rock, and gas to destroy anything in its path over an area of 230 square miles. Additionally, the debris from the volcano formed a avalanche which collided with nearby Spirit Lake, creating a tsunami which rose to heights of 850 ft., devastating nearby mountainsides. The 1980 eruption of Mount St. Helens claimed the lives of 57 people and millions of animals, while causing approximately $3 Billion in damages. The purpose of this site is to explain the formation, ecological effects, and geological significance of the 1980 Mount St. Helens eruption.