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Spirit Lake near Mount St. Helens

Spirit Lake near Mount St. Helens Famous Historical Events Geography STEM Disasters

This photograph depicts Spirit Lake, located near Mt. St. Helens, as it appeared before May 18, 1980.  

A popular tourist destination, before Mount St. Helens erupted, the once-gorgeous lake and its surrounding environment was scarred by volcanic debris (as depicted in this 4 October 1980 photo by Lyn Topinka working for the USGS):

https://upload.wikimedia.org/wikipedia/commons/7/78/MSH80_blast_area_spirit_lake_with_rainier_10-04-80_med.jpg

How could Spirit Lake have been so massively damaged? Were there warning signs that Mt. Saint Helens was likely to erupt?

The U.S. Geological Survey (USGS) relates what was happening inside the mountain in the months before its Plinian eruption on the 18th of May, 1980:

Magma began intruding into the Mount St. Helens edifice in the late winter and early spring of 1980. By May 18, the cryptodome (bulge) on the north flank had likely reached the point of instability, and was creeping more rapidly toward failure.

A magnitude-5+ earthquake was accompanied by a debris avalanche, which in turn unloaded the confining pressure at the top of the volcano by removing the cryptodome. This abrupt pressure release allowed hot water in the system to flash to steam, which expanded explosively, initiating a hydrothermal blast directed laterally through the landslide scar.

Because the upper portion of the volcano was removed, the pressure decreased on the system of magma beneath the volcano. A wave of decreasing pressure down the volcanic conduit to the subsurface magma reservoir, which then began to rise, form[ed] bubbles (degas), and erupt[ed] explosively, driving a 9-hour long Plinian eruption.

Robert Kimmel photographed the Plinian eruption of Mt. Saint Helens on May 18, 1980. His photo, taken for the USGS, depicts an aerial view of the eruption (as seen from the southwest).

Plinian eruption column from May 18, 1980 Mount St. Helens. Aerial view from the Southwest.

This massive eruption led to the deaths of 57 people and about $3 billion in other damages.

Click on the top image for a better view of the pre-eruption setting (with another Cascade stratovolcano, currently-at-rest Mt. Rainier, looming in the background).

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Author: Carole D. Bos, J.D. 5155stories and lessons created

Original Release: Oct 07, 2013

Updated Last Revision: Jul 17, 2018


Media Credits

Image online, courtesy the U.S. Geological Survey.

 

 

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"Spirit Lake near Mount St. Helens" AwesomeStories.com. Oct 07, 2013. Jul 17, 2018.
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