Mount St. Helens erupts catastrophically in Washington State
On this day · 18 May 1980
A magnitude-5.1 quake triggered the largest landslide in recorded history and a lateral blast that killed 57 people in seconds.
At 8:32 a.m. on May 18, 1980, a magnitude-5.1 earthquake shook loose the bulging north flank of Mount St. Helens in Washington State, unleashing the largest landslide in recorded history.
With the mountain’s side gone, pressurized gas and magma exploded sideways. The lateral blast flattened forests across some 230 square miles, scything down centuries-old trees and racing outward faster than the cars trying to outrun it. Ash rose more than 15 miles into the sky and drifted across the country.
Volcanologist David Johnston radioed “Vancouver! Vancouver! This is it!” moments before the blast claimed him.
The eruption killed 57 people and destroyed 200 homes, 47 bridges, and miles of highway and railway. It remains the deadliest and most economically destructive volcanic eruption in U.S. history — and it reshaped the science of forecasting eruptions.
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