From Washington To You
Gray eruption column rising from Mount St. Helens on May 18, 1980, with the collapsed north flank visible below the plume.
Photograph by Austin Post, U.S. Geological Survey, May 18, 1980. Public domain.

From Washington to you

Mount St. Helens

Mount St. Helens · Skamania County · May 18, 1980

On a clear May morning, the north side of the mountain gave way.

Before 1980, Mount St. Helens rose as a steep, symmetrical cone in the southern Cascades of Skamania County. That shape ended on May 18.

At 8:32 a.m. Pacific Daylight Time, a magnitude 5.1 earthquake accompanied the collapse of the volcano's bulging north flank. The landslide was the largest debris avalanche on Earth in recorded history. Most of it turned west down the North Fork Toutle River for about 14 miles.

Removal of that flank released pressure inside the volcano. A lateral blast roared north through what had been dense forest, and a Plinian eruption then ran for about nine hours. The debris avalanche took the upper 1,300 feet of the summit and left a horseshoe-shaped crater.

Ash blew east across Washington. Spokane, about 250 miles away, went dark in daytime. The mountain is still there — lower, open to the north, and one of five Washington volcanoes the state lists as high or very high threat. The sources below are the public USGS and Washington Geological Survey record of what happened.

  • Geography & Geology
  • History

Sources (3)

Last reviewed: September 20, 2026

Keep wandering

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    Washington's most remote active volcano is easy to miss from the cities — and has produced some of the biggest eruptions in the Lower 48.

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    The observatory sits in the center of the 1980 blast zone, about 5 miles north of the crater, and is named for the USGS volcanologist who died on duty that morning.

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    The 1980 debris avalanche raised the lake 64 meters, blocked its outlet, and forced a bedrock tunnel so the water would not break out down the Toutle.