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Mount Saint Helens

Page history last edited by PBworks 16 years, 4 months ago


Photo by US Geological Survey - Mount St. Helens from north looking over Mount Margaret

Mount Saint Helens is located in the state of Washington.

Elevation: 8,363ft


Estimation of Earliest Eruption: 10,000 BP (Before Present)

Earliest Recorded Eruption: 1831

Most Recent Eruption: 1990


Number of Eruptions in 20th and 21st Centuries: 5


Largest Eruption: 1855 BP VEI=6; 1800 VEI=5; 1980 VEI=5 with 56 deaths

(VEI stands for Volcanic Explosivity Index and is measured on a scale from 1-8 and takes into account the mountain height, amount of distruction, and the distance of thrown objects.)

Noteable Features: Bulge on the north face was removed by lateral blast and removed 1,306.8 ft from the mountain


Notable Statistic: Lateral blast destroyed 229 square miles and decimated several million dollars of timber.

Type of Volcano: Stratovolcano




Located in the state of Washington, Mount Saint Helens is a stratovolcano that reaches a height of 8,363 feet. Stratovolcanoes are usually "steep, conical volcanoes built by the eruption of viscous lava flows, tephra, and pyroclastic flows" and are sometinmes called composite volcanoes. This type of volcano is slow growing and usually takes hundreds of thousands of years to form. They have a variety of lava types and due to highly viscious lava are prone to explosions. Stratavolcanos usually have several vents and domes on the surface through which an eruption can occur at any given time.


Mrs. Simonson's References







Photo 31 The image “http://www.ngdc.noaa.gov/seg/hazard/stratoguide/img/St_Helens_Collage.jpg” cannot be displayed, because it contains errors.Photo 32

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