During the past 4,000 years, Mount St. Helens remains Mount St. Helens has a world-famous natural erupted more frequently laboratory for the study than any other volcano in of Earth’s processes and the Cascade Range. also nature’s response to catastrophe. Most of Mount St. Helens is younger than 3,000 During the 1980 to 1986 years old (younger than and the 2004 to 2008 the pyramids of Egypt). eruptions—Lava oozed onto the crater floor, building domes taller than Some Native American the Empire State Building names that refer to smoke and restoring 7 percent of at the volcano include— the volume lost in 1980. Lawala Clough, Low-We- Lat-Klah, Low-We-Not- Thlat, Loowit, Loo-wit, The Global Positioning Loo-wit Lat-kla, and System (GPS) instrument Louwala-Clough. that detected the settling of Mount St. Helens can detect movement of as 3,600 years ago—Native little as 1/16 of an inch and Americans abandoned uses less power than a hunting grounds refrigerator lightbulb. devastated by an enormous eruption four times larger than the During the 2004 to 2008 May 18, 1980 eruption. eruptions—Mount St. Helens settled one half 1792—Captain George inch due to magma Vancouver named the withdrawal beneath the volcano for Britain’s volcano. ambassador to Spain, Alleyne Fitzherbert, also October 2004 to January known as Baron St. Helens. 2008—Growing lava domes displaced and then 1975—U.S. Geological divided Crater Survey geologists into east and west lobes. forecasted that Mount St. The lobes moved Helens would erupt again, downslope as fast as 6 feet “possibly before the end of per day, converging below the century.” the a little more than three years later. March 20, 1980—A magnitude 4.2 earthquake signaled the September 2004—Mount St. reawakening of the volcano Helens reawakened, and it after 123 years. erupted continuously until January 2008. Spring 1980—Rising magma pushed the Since 1986, and volcano’s north flank rock accumulating in outward 5 feet per day. the deep, shaded crater formed Crater Glacier, Morning of May 18, 1980— the youngest glacier on The largest terrestrial Earth. landslide in recorded history reduced the summit October 1980 to 1986— by 1,300 feet and triggered Over the course of 17 a lateral blast. episodes, lava eruptions began filling the crater, Within 3 minutes, the lateral building a lava dome blast, traveling at more than that reached 876 feet 300 miles per hour, blew above the crater floor. down and scorched 230 square miles of forest. 1982—Mount St. Helens National Volcanic Within 15 minutes, a Monument was vertical plume of volcanic established for all to ash rose over 80,000 feet. observe both the awesome destruction and the remarkable Afternoon of May 18, recovery of plants and 1980—The dense ash animals. cloud turned daylight into darkness in eastern , causing Late spring through streetlights to turn on in fall 1980—Explosive Yakima and Ritzville. eruptions on May 25, June 12, July 22, August 7, and October 16–18 The volcanic ash cloud rocked Mount St. Helens drifted east across the and sent ash to distant United States in 3 days and communities. encircled Earth in 15 days.

Effects of the May 18, 1980 (volcanic mudflows) The May 18, 1980 Small plants and trees Thousands of birds, Late May 1980—Wind-dispersed The landscape devastated eruption continue today. filled rivers with rocks, eruption was the beneath winter snow, and mammals, reptiles, spiders and scavenging beetles by the eruption has Biologists help wild salmon sand, and mud, damaging 27 most economically roots protected by soil, amphibians, and millions were among the first animals to evolved into a rich and and steelhead by giving bridges and 200 homes and destructive volcanic survived the May 18, 1980 of hatchery fingerlings return to the Mount St. Helens diverse habitat for plants them a tank-truck ride to the forcing 31 ships to remain event in U.S. history. eruption and now thrive. perished in the eruption. area. and animals. pristine, clear creeks above in ports upstream. sediment-choked rivers.

Photograph by Michael Doukas, USGS, July 22, 1980

By Carolyn Driedger1, Liz Westby1, Lisa Faust1, Peter Frenzen2, Jeanne Bennett3, Michael Clynne1 Available from U.S. Geological Survey, Information Services, 2010 Box 25286, Federal Center, Denver, CO, 80225, 1-888-ASK-USGS Digital files available at http://pubs.usgs.gov/gip/103/ 1U.S. Geological Survey, 2U.S. Forest Service, 3Mount St. Helens Institute U.S. Department of the Interior March 2010 U.S. Geological Survey General Information Product 103