During the past 4,000 years, 

Mount St. Helens has 

erupted more frequently 

than any other volcano in 

the Cascade Range.

Most of Mount St. Helens 

is younger than 3,000 

years old (younger than 

the pyramids of Egypt).

Some Native American 

names that refer to smoke 

at the volcano include—

Lawala Clough, Low-WeLat-Klah, Low-We-NotThlat, Loowit, Loo-wit, 

Loo-wit Lat-kla, and 

Louwala-Clough. 

3,600 years ago—Native 

Americans abandoned 

hunting grounds 

devastated by an 

enormous eruption four 

times larger than the 

May 18, 1980 eruption.

1792—Captain George 

Vancouver named the 

volcano for Britain’s 

ambassador to Spain, 

Alleyne Fitzherbert, also 

known as Baron St. Helens. 

1975—U.S. Geological 

Survey geologists 

forecasted that Mount St. 

Helens would erupt again, 

“possibly before the end of 

the century.”

Morning of May 18, 1980—

The largest terrestrial 

landslide in recorded 

history reduced the summit 

by 1,300 feet and triggered 

a lateral blast.

Spring 1980—Rising 

magma pushed the 

volcano’s north flank 

outward 5 feet per day.

March 20, 1980—A magnitude 

4.2 earthquake signaled the 

reawakening of the volcano 

after 123 years.

Within 3 minutes, the lateral 

blast, traveling at more than 

300 miles per hour, blew 

down and scorched 230 

square miles of forest.

Afternoon of May 18, 

1980—The dense ash 

cloud turned daylight 

into darkness in eastern 

Washington, causing 

streetlights to turn on in 

Yakima and Ritzville.

Within 15 minutes, a 

vertical plume of volcanic 

ash rose over 80,000 feet.

The volcanic ash cloud 

drifted east across the 

United States in 3 days and 

encircled Earth in 15 days.

Lahars (volcanic mudflows) 

filled rivers with rocks, 

sand, and mud, damaging 27 

bridges and 200 homes and 

forcing 31 ships to remain 

in ports upstream.

Thousands of birds, 

mammals, reptiles, 

amphibians, and millions 

of hatchery fingerlings 

perished in the eruption.

The May 18, 1980 

eruption was the 

most economically 

destructive volcanic 

event in U.S. history.

Small plants and trees 

beneath winter snow, and 

roots protected by soil, 

survived the May 18, 1980 

eruption and now thrive.

Effects of the May 18, 1980 

eruption continue today. 

Biologists help wild salmon 

and steelhead by giving 

them a tank-truck ride to the 

pristine, clear creeks above 

sediment-choked rivers.

Late May 1980—Wind-dispersed 

spiders and scavenging beetles 

were among the first animals to 

return to the Mount St. Helens 

area.

The landscape devastated 

by the eruption has 

evolved into a rich and 

diverse habitat for plants 

and animals.

Late spring through 

fall 1980—Explosive 

eruptions on May 25, 

June 12, July 22, August 

7, and October 16–18 

rocked Mount St. Helens 

and sent ash to distant 

communities. 

October 1980 to 1986—

Over the course of 17 

episodes, lava eruptions 

began filling the crater, 

building a lava dome 

that reached 876 feet 

above the crater floor. 

Since 1986, snow and 

rock accumulating in 

the deep, shaded crater 

formed Crater Glacier, 

the youngest glacier on 

Earth. 

September 2004—Mount St. 

Helens reawakened, and it 

erupted continuously 

until January 2008.

During the 2004 to 2008 

eruptions—Mount St. 

Helens settled one half

inch due to magma 

withdrawal beneath the 

volcano.

Mount St. Helens remains 

a world-famous natural 

laboratory for the study 

of Earth’s processes and 

also nature’s response to 

catastrophe.

The Global Positioning 

System (GPS) instrument 

that detected the settling 

of Mount St. Helens can 

detect movement of as 

little as 1/16 of an inch and 

uses less power than a 

refrigerator lightbulb.

During the 1980 to 1986 

and the 2004 to 2008 

eruptions—Lava oozed 

onto the crater floor, 

building domes taller than 

the Empire State Building 

and restoring 7 percent of 

the volume lost in 1980.

1982—Mount St. Helens 

National Volcanic 

Monument was 

established for all to 

observe both the 

awesome destruction 

and the remarkable 

recovery of plants and 

animals.

October 2004 to January 

2008—Growing lava 

domes displaced and then 

divided Crater Glacier 

into east and west lobes. 

The ice lobes moved 

downslope as fast as 6 feet 

per day, converging below 

the lava dome a little more 

than three years later.

U.S. Department of the Interior March 2010

U.S. Geological Survey General Information Product 103

Available from U.S. Geological Survey, Information Services, 

Box 25286, Federal Center, Denver, CO, 80225, 1-888-ASK-USGS

Digital files available at http://pubs.usgs.gov/gip/103/

By

Carolyn Driedger1, Liz Westby1, Lisa Faust1, Peter Frenzen2, Jeanne Bennett3, Michael Clynne1

2010

1

U.S. Geological Survey, 2U.S. Forest Service, 3Mount St. Helens Institute

Photograph by Michael Doukas, USGS, July 22, 1980