Mount St. Helens

Mount St. Helens

The May 18, 1980 eruption was the most economically destructive volcanic event in U.S. history.

On March 20, 1980 a magnitude 4.2 earthquake signaled the reawakening of the volcano after 123 years.

The dense ash cloud created by the explosion on May 18, 1980 turned daylight into darkness in eastern Washington. In Yakima and Ritzville it caused street lights to turn on.

The volcanic ash cloud drifted had drifted east and covered the US in 3 days and only took 15 days to encircle the Earth

Since 1986, snow and rock accumulating in the deep, shaded crater formed Crater Glacier, have formed the youngest glacier on Earth.

During the 2004 to 2008 eruptions, Mount St. Helens settled one half inch due to magma loss beneath the volcano.

Mount St. Helens re awakened in Septeber of 2004, and erupted continuously until January 2008.

http://pubs.usgs.gov/gip/103/