Mount St. Helens was once enjoyed for its serene beauty and was considered one of America’s most majestic volcanoes because of its perfect cone shape, similar to Japan’s beloved Mount Fuji. Nearby residents assumed that the mountain was solid and enduring. That perception changed during the early spring of 1980. Then, on May 18, 1980, following 2 months of earthquakes and small explosions, the volcano’s over-steepened north flank collapsed in a colossal landslide and triggered a near-horizontal blast, followed by a powerful vertical eruption. The high-speed, rock-filled, and gas-charged blast quickly evolved into a gravitationally driven pyroclastic flow, which leveled millions of trees, stripped them of their branches and bark, and scoured soil from bedrock. The vertical eruption that followed fed a towering plume of ash for more than 9 hours. Winds carried the ash from the volcano and deposited it hundreds of miles away. Lahars (volcanic mudflows) buried river valleys. These catastrophic events caused the worst volcanic disaster in the recorded history of the conterminous United States. The events violently transformed Mount St. Helens and left a lasting impression on the hearts and minds of people living in the Pacific Northwest and beyond.
- Digital Object Identifier: 10.3133/fs20203031
- Source: USGS Publications Warehouse (indexId: fs20203031)