Mount St. Helens is a young, active stratovolcano in southwestern Washington within the Cascade Volcanic Arc and the Pacific Ring of Fire. Known by Indigenous names long before receiving its English name through George Vancouver’s surveys, it was once famed for its near-symmetrical, snow-covered form. Its defining modern event came on May 18, 1980, when an earthquake triggered a huge debris avalanche and lateral eruption that lowered the summit, opened a broad crater, killed 57 people, and caused enormous destruction, making it the most economically destructive volcanic event in United States history. Activity continued until 2008, and the volcano remains a closely studied natural laboratory and popular climbing destination.