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The Eruption of Mount St. Helens

March 20-May 18, 1980

Mount St. Helens rises above Spirit Lake in this Northern Pacific Railway picture, released a few years before the eruption.
Mount St. Helens before the eruption

Located in the state of Washington, Mount St. Helens had been quiet for 123 years when, on March 20, 1980, it was shaken by an earthquake. Over the next seven days more than 100 major earthquakes and thousands of small ones were recorded. On March 27, just after noon, a boom came from the mountain that was heard miles away, and steam and ash began shooting into the air. Steam, gases, ash, ice, and rocks continued to spew from the volcano for the next few weeks, and small earthquakes and explosions continued to rock the mountain and surrounding area.

Volcanologists and other scientists began flocking to the area, as did tourists. The scientists warned that a major eruption was imminent, and people living on the mountain were evacuated. A "Red Zone" was marked offmon a map, and only scientists were allowed inside. As time went by and nothing dramatic happened, however, residents began defying the Red Zone, and even began selling maps showing tourists how to avoid the barricades by using logging roads.

Sightseers' cars were stopped by a police roadblock on March 29. Some people left their cars and hiked into the Red Zone to get a look at the rumbling mountain.
sightseers try to get a view of Mount St. Helens

By March 30 a 200-foot-wide crater at the summit had been "joined" by a second, smaller one.
Mount St. Helens crater of May 30

On March 31, the southwest flank of Mount St. Helens was covered with near pristine snow, while the northeast flank was coated with ash.
Mount St. Helens on March 31

By April 6 the two craters had merged into a single 1,500-foot-wide one.
Mount St. Helens

At 8:30 a.m. on May 18, Mount St. Helens was rattled by an earthquake, followed by several smaller ones. The quakes triggered a massive landslide that roared down the north slope. At 8:32, the top of the mountain exploded with a blast that was heard 200 miles away. Seconds later the north slope exploded out to the side. The second explosion instantly leveled trees and structures over more than 150 square miles, and triggered a massive mudflow that lasted for hours and caused even more devastation "downstream" from the mountain.

The "big blast" in an aerial view from the west. The ash plume rose over 60,000 feet into the atmosphere.
the explosion of Mount St. Helens

Fumaroles were all that was left of Spirit Lake after the explosions and mudslide.
Spirit Lake after the eruption

Some of the giant trees torn up and carried by the mudslide that followed the eruption.
mudflow debris left by Mount St. Helens

The mudslide tore this bridge completely off its moorings and carried it downstream.
bridge destroyed by mudslide

A soldier searches for possible bodies in a debris- and ash-covered car.
searching for victims

Volcanologist David Johnston was monitoring the volcano's activity from an observation post about 5 miles north of the crater on May 18, and reported the blast -- "Vancouver, Vancouver. This is it!" -- just before his radio went silent.
David Johnston

84-year-old Harry Truman, shown here about a week before the eruption, refused to leave his lodge on Spirit Lake and was given special permission to stay. He lost his life on the mountain he loved.
Harry Truman

When Mount St. Helens blew, 1.3 billion cubic yards of ash shot up 12 miles into the air, and also billowed out. Many people who weren't killed by the explosion or mudflow died in the suffocating ash "fallout." As the ash cloud moved with the wind northeastward across the sky, it "turned day into night" for hundreds of towns in its path, some over a hundred miles away.

News photographer Reid Blackburn's body was found in his car, which had been all but buried by ash.
Reid Blackburn's car

The Yakima Valley College baseball team was in the middle of a game when the cloud of ash arrived. The sky got so dark that even the field's lights proved too dim and the game was ultimately called.
playing baseball during an ash fall

Masks became part of the formal attire for this bride and groom who chose to go ahead with their wedding despite the ashcloud that descended on Yakima, Washington.
getting married during an ash fall

A surplus army mask became fashionable attire in Portland, Oregon, after the eruption.
Portland, Oregon, during the ash fall

Residents of Richland, Washington, 130 miles east of Mount St. Helens, saw this terrifying ash cloud darken their sky.
Richland, Washington, experiencing an ash cloud

PICTURE SOURCE
Rita Golden Gelman, Mount St. Helens: The Big Blast New York, New York: Scholastic Book Services, 1981

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The Robinson Library >> Science >> Geology >> Dynamic and Structural Geology

This page was last updated on 02/02/2018.