This Washington Volcano’s 1980 Explosion Sent Ash Across 11 States & Flattened Forests in Minutes

Mount St. Helens, Washington

The warning signs were there for months, but nothing could prepare the Pacific Northwest for what Mount St. Helens had in store.

When the mountain finally erupted on a spring morning in 1980, it unleashed forces that reshaped the land and took 57 lives.

This is the story of that fateful day.

The Warning Signs

Mount St. Helens slept quietly for over a century after its last eruptions in the 1840s. That peaceful slumber ended on March 15, 1980.

A series of small earthquakes began rattling the mountain that day. Scientists rushed to install monitoring equipment.

On March 20, a stronger magnitude 4.2 earthquake shook the mountain.

One week later, on March 27, the first visible eruption occurred. Steam explosions blasted through the summit ice cap.

Within days, the newly formed crater stretched 1,300 feet across and large cracks split the entire summit area.

North Flank Bulge Grew Daily

By mid-April, scientists spotted a concerning bulge forming on the north slope. Geologists called this swelling a cryptodome, which is magma pushing up beneath the surface.

The mountain’s north face stretched outward at about 5 feet per day throughout April. By May 17, the north flank had swelled outward approximately 450 feet.

USGS volcanologist David Johnston Mount St. Helens compared the bulging mountain to “a keg of dynamite with the fuse lit.”

Sunday Morning Catastrophe

Sunday, May 18, 1980, dawned clear and bright. At precisely 8:32 a.m., a magnitude 5.1 earthquake struck beneath Mount St. Helens.

This tremor triggered the most destructive volcanic eruption in U.S. history and destabilized the entire north face.

The weakened north slope collapsed in the largest landslide ever recorded. This massive wall of rock, ice, and soil slid away at tremendous speed.

The landslide removed the top 1,300 feet of the mountain in seconds. Where a symmetrical peak once stood, a gaping horseshoe-shaped crater remained.

The new crater measured nearly 2 miles wide and 2,084 feet deep.

The Lateral Blast Levels Forests

When the north face collapsed, it released pressure on the magma chamber like uncorking a shaken bottle. The mountain exploded sideways through the new opening.

Rather than shooting upward like most eruptions, Mount St. Helens blasted laterally at hurricane force. The superheated mixture of gas and rock fragments accelerated to speeds over 300 mph.

It easily overtook the massive landslide racing down the mountain. The sideways explosion flattened everything across 230 square miles.

Within 6 miles of the summit, no trees remained standing in forests that had thrived for centuries. Trees farther out were knocked flat, all pointing away from the blast center.

Ash Cloud Darkens Cities

Following the lateral blast, Mount St. Helens pumped ash high into the atmosphere. Within 15 minutes, the eruption column soared more than 15 miles above the mountain.

The towering ash plume reached 80,000 feet. Prevailing winds carried the dense cloud eastward across Washington State.

During nine hours of continuous eruption, the volcano ejected approximately 540 million tons of ash, which spread across more than 22,000 square miles.

By noon, cities as far away as Spokane – 250 miles from the volcano – plunged into darkness. Residents described the experience as night falling at midday.

The ash eventually circled the globe within two weeks.

Scientist’s Final Radio Call

Volcanologist David Johnston monitored Mount St. Helens from an observation post 6 miles north of the summit.

The 30-year-old USGS scientist had relieved a colleague at the site just 13 hours before the eruption. Johnston knew the dangers but believed scientific monitoring was worth the risk.

When the eruption began, Johnston made a final radio transmission: “Vancouver! Vancouver! This is it!” Seconds later, the lateral blast overwhelmed his position at speeds exceeding 300 mph.

Johnston had advocated strongly for keeping the area closed to the public. His warnings convinced authorities to maintain the closure, saving thousands of lives.

Fifty-Seven Lives Lost

The 1980 eruption of Mount St. Helens killed 57 people, making it the deadliest volcanic event in U.S. history. Most victims died from asphyxiation after inhaling scorching ash and gases.

Others perished from thermal burns or blast injuries. Among those lost was Harry R. Truman, an 83-year-old innkeeper who refused to leave his lodge near Spirit Lake.

The debris avalanche buried his property under hundreds of feet of material. Photographers Reid Blackburn and Robert Landsburg also perished while documenting the eruption.

Landsburg protected his film by placing his camera in his backpack before being overcome.

Wildlife and Forest Destruction

The eruption devastated animal populations across the blast zone and nearly 7,000 large mammals perished, including deer, elk, and bears.

Birds and small mammals died by the thousands. Fish populations in Spirit Lake were eliminated when the lake temperature rose dramatically.

Approximately 4 billion board feet of timber – enough to build 300,000 homes – was destroyed in moments.

Massive lahars – volcanic mudflows with the consistency of wet concrete – swept down river valleys at high speeds. These flows carried trees, boulders, and buildings, destroying 47 bridges and 185 miles of highway.

The mudflows reshaped entire watersheds, altering the landscape for generations.

Life Returns to the Wasteland

When scientists first surveyed the blast zone, they expected recovery would take decades. To their surprise, life began returning within weeks.

By the late 1980s, the first significant recovery appeared in areas farthest from the volcano. Plants established themselves, followed by insects and small mammals.

Today, the diversity of plant and animal species actually exceeds what existed before the eruption.

Memorial at Johnston Ridge

Following David Johnston’s death, the ridge where he lost his life was renamed in his honor. Johnston Ridge Observatory stands at this location, 5 miles north of the volcano.

Inside the facility, sensitive equipment tracks seismic activity, ground deformation, and gas emissions. Data feeds directly to scientists at the USGS Cascades Volcano Observatory.

In May 2023, heavy rains triggered a landslide that destroyed the Spirit Lake Outlet Bridge. This damage has closed access to Johnston Ridge Observatory until 2027.

Visiting Mount St. Helens National Volcanic Monument

You’ll find the monument in Gifford Pinchot National Forest, southwestern Washington State. At the site, you’ll be able to see the crater, lava domes, and remarkable landscape recovery.

Several viewpoints and visitor centers provide different perspectives on the volcano. The Mount St. Helens Visitor Center at Silver Lake, operated by Washington State Parks, is located 30 miles west of the volcano.

This facility offers exhibits on the eruption and ecological recovery. Ape Cave, one of North America’s longest lava tubes at 2.5 miles, remains open to visitors year-round.

Anyone wishing to hike above 4,800 feet elevation, including climbs to the summit, must obtain a permit.

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