Mount St. Helens is most famous for its major eruption on May 18, 1980, the deadliest and most economically destructive volcanic event in U.S. history. Fifty-seven people were killed; 200 homes, 47 bridges, of railways, and of highway were destroyed. A massive debris avalanche, triggered by a magnitude 5.1 earthquake, caused a lateral eruption that reduced the elevation of the mountain's summit from to , leaving a  wide horseshoe-shaped crater. The debris avalanche was in volume.The 1980 eruption caused terrestrial ecosystems near the volcano to diminish biological production. By contrast, aquatic ecosystems in the area greatly benefited from the amounts of ash, allowing life to multiply rapidly. Six years after the eruption, most lakes in the area went back to their normal state.