Mount St. Helens is a volcano in Washington State, and it’s most famous for its catastrophic eruption on May 18, 1980—one of the most powerful and destructive volcanic eruptions in U.S. history.
Here’s a breakdown of what happened:
Before the Eruption
Mount St. Helens was dormant for over a century before 1980.
In March 1980, earthquakes and steam explosions started, warning that magma was rising.
A huge bulge formed on the north side of the mountain—growing 5 feet a day as pressure built.
May 18, 1980 – The Eruption
At 8:32 AM, a magnitude 5.1 earthquake triggered a massive landslide—the largest in recorded history.
This caused the volcano’s north face to collapse, releasing pressure instantly.
A lateral blast of hot gas, ash, and rock shot sideways at 300+ mph.
A vertical plume of ash rose over 15 miles into the sky.
Aftermath
57 people died, including volcanologist David A. Johnston and local resident Harry R. Truman, who refused to evacuate.
Hundreds of square miles of forest were flattened.
Lahars (mudflows) raced down rivers, destroying bridges and roads.
Ashfall blanketed towns across the Pacific Northwest, even reaching as far as the Midwest.
Today
The mountain lost about 1,300 feet of elevation, leaving a massive crater.
It remains an active volcano and is monitored constantly.
A lava dome has grown inside the crater over the years from smaller eruptions.
It’s now a popular site for science, hiking, and tourism, and a powerful reminder of nature’s force.
Want a diagram or satellite image of what it looked like before vs. after?