Week 4 - Mout St. Helens - Mike Loranger

A good portion of my rather large family lives in the pacific northwest, specifically Wenatchee, WA a few hours outside of Seattle.  During trips to see family, we have driven as close as I have ever been to a volcano – Mount St Helen’s.  It hasn’t really been all that long since Mount St. Helen’s erupted explosively, throwing nearly a cubic kilometer of ash and rock into the air.  You can still see the horseshoe-shaped crater, between 1 and 2 miles wide, carved out of the volcano. 

Bulge on the north side of Mount St. Helens developed as magma pushed up within the peak before May 18, 1980. View from the northeast.

The volcano has layers of ash, pumice, and basalt that indicate varying degrees of viscosity and gas content.  The ash and pumice indicate an explosive eruption caused by highly viscous lava with high gas content.  The basalt was likely formed by low viscosity lava flows, due to its low silica content, that move relatively quickly.

Steam-blast (phreatic) eruption from the summit crater of Mount St. Helens on April 6, 1980. Aerial view to the southwest.

While the volcano remained active up until 2008, it is no longer considered in imminent danger of an imminent eruption.  Mount St. Helens is still considered an active volcano and regularly have seismic activity below the surface.  The volcano is located at the edge of the Juan de Fuca plate, where it meets the North American as part of the Cascade Range.  The fact that this area is at the edges of these plates and has frequent earthquakes, indicates that there will likely be continued eruptions well into the future.  In fact, this area is dotted with many, smaller volcanos.

Mount St. Helens crater, with the Pumice Plain in the foreground. October 2004

References

1980 Cataclysmic Eruption. (n.d.). Retrieved November 25, 2019, from https://volcanoes.usgs.gov/volcanoes/st_helens/st_helens_geo_hist_99.html

Cascades Volcano Observatory (CVO). (n.d.). Retrieved November 25, 2019, from https://volcanoes.usgs.gov/observatories/cvo/

Why Study Cascade Volcanoes? (n.d.). Retrieved November 25, 2019, from https://volcanoes.usgs.gov/observatories/cvo/cascade_volcanoes.html

Wikipedia contributors. (2019a, November 6). Mount St. Helens. Retrieved November 25, 2019, from https://en.wikipedia.org/wiki/Mount_St._Helens

Wikipedia contributors. (2019b, November 17). Cascade Range. Retrieved November 25, 2019, from https://en.wikipedia.org/wiki/Cascade_Range

www.Mount St. Helens.com - Mount St. Helens Discovery Group, LLC. (n.d.). MountStHelens.com Information Resource Center & Visitor Guide. Retrieved November 25, 2019, from http://mountsthelens.com/