Mount St. HelensBy Maha, Camille, and Esther

Type of Volcano

Mount St. Helens is an active stratovolcano (composite volcano).

Geographic Location

Latitude and Longitude:46.2000° N, 122.1892° W

Mount St. Helens

Nearest Major City

• Nearest City: Vancouver, Washington

• Population: 161,791

• Distance from Volcano: 47 miles

Eruptions

• Most Recent Eruption: 2004 – July 10, 2008

• Most Destructive Eruption: May 18, 1980

Other Events Associated with Eruption

• In 1980 there was an Earthquake with the magnitude of 5.1 a mile below the volcano, which set the volcano off

• Also during the 1980 eruption an avalanche was caused which would be recorded as the largest landslide debris avalanche in historic time

Tectonic Plates

Formation of Volcano

New crust is continually being pushed away from divergent boundaries (where sea-floor spreading occurs), increasing Earth's surface. But the Earth isn't getting any bigger. What happens, then, to keep the Earth the same size? The answer is subduction.

In locations around the world, ocean crust subducts, or slides under, other pieces of Earth's crust. The boundary where the two plates meet is called a convergent boundary. Deep trenches appear at these boundaries, caused by the oceanic plate bending downward into the Earth.

Deep below the Earth's surface, subduction causes partial melting of both the ocean crust and mantle as they slide past one another. This melting generates magma that makes its way to the surface, producing volcanoes, such as Mt. St. Helens. Most of the subducting plate continues into the mantle, perhaps to reappear much later at a distant divergent boundary.

Other Interesting Facts

• During the past 4,000 years Mount St. Helens has erupted more frequently than any other volcano

• Mount St. Helens erupted continuously from 2004-2008

• Mount St. Helens is 8,364 ft. but used to be 9,677 ft.

• Mount St. Helens was named after a British soldier• On May 18,1980 a vertical plume of ash rose over

80,000 ft.

Picture URLs

Tile Page: http://en.wikipedia.org/wiki/Mount_St._HelensType of Volcano: http://entequilaesverdad.blogspot.com/2010/05/happy-30th-anniversary-mount-saint.htmlGeographic Location: http://webspace.ship.edu/cjwolt/geology/cas.htmNearest Major City: http://en.wikipedia.org/wiki/Mount_St._HelensEruptions: http://www.boston.com/bigpicture/2010/05/mount_st_helens_30_years_ago.htmlOther Events: http://www.worldtravelattractions.com/mount-saint-helens-eruptions/Formation: http://www.pbs.org/wgbh/aso/tryit/tectonics/convergent.htmlFacts: http://en.wikipedia.org/wiki/1980_eruption_of_Mount_St._Helens