Week 4 - Vocanos

After learning about volcanos during my physical geology class, I was so interested in the topic that I decided to go and see one for myself. After a little bit of research I decided to go to Washington state and visit Mount St. Helens. I was surprised to discover that Mount St. Helens had erupted not to long ago, to be precise, it last erupted on May 18, 1980. According to the informational pamphlets, Mount St. Helens' eruption is often considered as the most disastrous volcanic eruption in US history. This is how the mountain looks like today.

Mount St. Helens is part of the Cascade Volcanic Arc. The Cascade Arc extends from southwestern British Columbia through Washington and Oregon to Northern California.  There are about 18 major volcanos in this area.

Volcanism occurs in this area due to subduction of the Juan de Fuca plate off the western coast of North America. As the plate slides under the continental plate, it dips deeper and deeper and it gets hotter. The water released by the minerals lowers the melting point of the mantle, and the solid mantle begins to melt until eventually erupting.

The 1980 eruption of Mount St. Helens was a major volcanic explosion. The eruption was so powerful that removed the upper 1,300 feet of the summit. Everything within eight miles of the blast was wiped out. The shockwave expanded for another 19 miles leveling the forest's century-old trees. An area of 230 square miles was devastated by the blast. 

Magma began intruding into the mountain's edifice earlier that year. By May, the bulge had reached the point of instability. When an earthquake accompanied by an avalanche unloaded the confining pressure on the mountain, the pressure release ultimately triggered the volcano to blast through the landslide scar.

The US Geological Survey (USGS) has been keeping an eye on the volcanos activity since the last eruption. They don't believe we have to worry about another eruption just yet, but recent earthquakes do remind them the mountain could be recharging. So we better keep an eye on Mount St. Helens as well.

Sources: usgs.gov, livescience.com, wire.com