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.

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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.


57

Lives Lost


$1.1Billion

Damage Costs


9600feet

Height Before Eruption


8300feet

Height After Eruption


200

Homes Destroyed


90mph

Mudflows Speed


5400000tons

Estimated Ash


2200sq miles

Ash Covered


185miles

Roads Destroyed


15miles

Railways Damaged


Mt. St. Helens 40th Anniversary Events


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.
May 18, 0001

Mt. St. Helens is Born 3,000 Years Ago

Most of Mount St. Helens is younger than 3,000 years old (younger than the pyramids of Egypt) Loowit Some Native American names that refer to smoke […]
January 1, 1792

Mt. 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 […]
February 1, 1800

1800’s Explosive Eruption

Mount St. Helens erupts explosively in 1800; intermittently from 1831 to 1857; then enters a 123-year quiet phase.
March 27, 1980

March 1980 Magnitude 4.1 earthquake

Magnitude 4.1 earthquake signals reawakening. Eruption of ash and steam March 27, opening a 250-foot crater.
May 13, 1980

May 1980 Swelling North Face

Swelling on the north face creates an ominous bulge. Hundreds of earthquakes shake the mountain.
May 18, 1980

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 […]
June 13, 1980

June-October 1980 New Dome Forms

Continuing eruptions destroy a lava dome inside the crater. A new dome forms.
September 3, 1980

September 1980 Timber Salvage

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

Aug. 27, 1982 National Monument

President Reagan signs a bill establishing the 110,000-acre Mount St. Helens National Volcanic Monument.
May 13, 1987

1987 Summit Reopens

Volcano summit reopened to recreational climbing.
June 1, 1987

1987 Sediment Dam Built

U.S. Army Corps of Engineers builds a dam to hold back sediment carried downstream by the North Fork of the Toutle.
May 13, 1994

1994 Memorial Hwy Opens

The reconstructed 52-mile-long Spirit Lake Memorial Highway opens to traffic, connecting Castle Rock to stunning viewpoints in the blast zone.
May 13, 1997

1997 Johnston Ridge Opens

The U.S. Forest Service opens the Johnston Ridge Observatory five miles from the crater.
August 2, 2004

Oct. 2, 2004 Evacuation of Johnston Ridge

Sustained tremors inside the mountain indicate movement of magma. The Forest Service evacuates visitors from Johnston Ridge Observatory.
September 23, 2004

Sept 23, 2004 Flurry of Earthquakes

The mountain stirs with a flurry of earthquakes.
October 11, 2004

Oct. 11, 2004 Lava Emerges

Lava emerges on the crater surface for the first time in 18 years.
November 5, 2004

Nov. 5, 2004 26 Million Cubic Yards

New dome reaches 26 million cubic yards.
January 16, 2005

Jan. 16, 2005 Explosive Eruption

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

March 8, 2005 Ash Plume

The mountain sends ash and steam to an altitude of 36,000 feet, wowing spectators just before sunset.’
May 13, 2005

2005 – Present Seismic 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 […]
February 13, 2008

Early 2008 Dome Building

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

July 13, 2008 Eruptions End

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



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