Mt. St. Helens Eruption 40 Year Anniversary

Mount St. Helens erupted on May 18, 1980. The volcano, located in southwestern Washington, used to be a beautiful symmetrical cone about 9,600 feet (3,000 meters) above sea level.

Header Image Credit - By Gregg M. Erickson (talk · contribs) - Own work, CC BY 3.0,

Mt. St. Helens Changed Our World.

Mt. St. Helens Eruption 40 Year Anniversary

Mount St. Helens erupted on May 18, 1980 at 8:32am

Vancouver! Vancouver! This is it!

On March 1, 1980, a new system of seismographs at the University of Washington went into operation to monitor earthquake activity in the Cascades. On March 20, it recorded a magnitude-4.2 earthquake deep beneath Mount St. Helens, inaugurating a round-the-clock watch that was to save many lives. From March 25 to March 27, quakes of magnitude 4.0 rocked the mountain as many as three times a day, and smaller quakes occurred several times every hour.

At 8 a.m. PST on March 27, the U.S. Geological Survey issued an official Hazard Watch for Mount St. Helens; around noon, the first eruption of steam from the summit sent a column of ash and steam 6,000 feet (1,829 meters) into the air. Twin fissures opened on the mountain’s north face.

On the morning of May 18, USGS volcanologist David A. Johnston, camped on the ridge with his lasers, radioed in his regular 7 a.m. report. The changes to the bulging mountain were consistent with what had been reported several times daily since the watch began. At 8:32, a magnitude-5.1 earthquake registered on the seismographic equipment. His excited radio message, “This is it!” was followed by a stream of data. It was his last transmission; the ridge he camped on was within the direct blast zone.


Lives Lost


Damage Costs


Height Before Eruption


Height After Eruption


Homes Destroyed


Mudflows Speed


Estimated Ash

2200sq miles

Ash Covered


Roads Destroyed


Railways Damaged

Mt. St. Helens 40th Anniversary Events

There are no upcoming events at this time.

On Shaky Ground

Mt. St. Helens Eruption Timeline

Mount St. Helens is most notorious for its major eruption on May 18, 1980, the deadliest and most economically destructive volcanic event in U.S. history.
  • 3,000 years agoMt. St. Helens is born

    Most of Mount St. Helens is younger than 3,000 years old (younger than the pyramids of Egypt)
  • 3,000 years agoLoowit

    Some Native American names that refer to smoke at the volcano include— Lawala Clough, Low-We- Lat-Klah, Low-We-Not- Thlat, Loowit, Loo-wit, Loo-wit Lat-kla, and Louwala-Clough.
  • 1792Mt. St. Helen's is named by Captain Vancouver

    Captain George Vancouver named the volcano for Britain’s ambassador to Spain, Alleyne Fitzherbert, also known as Baron St. Helens. Alleyne FitzHerbert, 1st Baron St Helens PC was a British diplomat. He was Minister Plenipotentiary to Russia from 1783 to 1788, appointed Chief Secretary for Ireland and a member of the Privy Council (Great Britain & Ireland) in 1787, serving in the former position until 1789. He was Minister plenipotentiary to Spain from 1790 to 1794.
  • 1800'sExplosive Eruption

    Mount St. Helens erupts explosively in 1800; intermittently from 1831 to 1857; then enters a 123-year quiet phase.
  • March 1980Magnitude 4.1 earthquake

    Magnitude 4.1 earthquake signals reawakening. Eruption of ash and steam March 27, opening a 250-foot crater.
  • May 1980Swelling North Face

    Swelling on the north face creates an ominous bulge. Hundreds of earthquakes shake the mountain.
  • 8:32 a.m. May 18, 1980 Historic Modern Eruption

    St. Helens’ eruption, with its lateral blast, debris avalanche, mudflows and floods, claims 57 lives and obliterates virtually everything within an eight-mile radius. An ash column rises 15 miles and travels east at 60 mph, circling the globe in two weeks.
  • June-October 1980New Dome Forms

    Continuing eruptions destroy a lava dome inside the crater. A new dome forms.
  • September 1980Timber Salvage

    Weyerhaeuser Co. begins salvaging some of the 62,000 acres of timber and young plantations damaged by the blast.
  • Aug. 27, 1982National Monument

    President Reagan signs a bill establishing the 110,000-acre Mount St. Helens National Volcanic Monument.
  • 1987Summit Reopens

    Volcano summit reopened to recreational climbing.
  • 1987Sediment Dam Built

    U.S. Army Corps of Engineers builds a dam to hold back sediment carried downstream by the North Fork of the Toutle.
  • 1994Memorial Hwy Opens

    The reconstructed 52-mile-long Spirit Lake Memorial Highway opens to traffic, connecting Castle Rock to stunning viewpoints in the blast zone.
  • 1997Johnston Ridge Opens

    The U.S. Forest Service opens the Johnston Ridge Observatory five miles from the crater.
  • Sept 23, 2004Flurry of Earthquakes

    The mountain stirs with a flurry of earthquakes.
  • Oct. 2, 2004Evacuation of Johnston Ridge

    Sustained tremors inside the mountain indicate movement of magma. The Forest Service evacuates visitors from Johnston Ridge Observatory.
  • Oct. 11, 2004Lava Emerges

    Lava emerges on the crater surface for the first time in 18 years.
  • Nov. 5, 200426 Million Cubic Yards

    New dome reaches 26 million cubic yards.
  • Jan. 16, 2005Explosive Eruption

    A 17-minute explosive eruption destroys instruments inside the crater.
  • March 8, 2005Ash Plume

    The mountain sends ash and steam to an altitude of 36,000 feet, wowing spectators just before sunset.’
  • Early 2008Dome Building

    Dome-building slows to a halt and seismic activity drops.
  • July 13, 2008Eruptions End

    Scientists declare that the 2004-2008 eruption has ended after building a new, 125-million-cubic-yard lava dome.
  • 2005 - PresentSeismic Activity Resumes

    Mount St. Helens continues to experience low rates of seismicity, low emissions of steam and volcanic gases, minor production of ash, and the growth of a new lava dome inside the crater.

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