Today in the 20th Century: The Most Disastrous Volcanic Eruption in U.S. History – Mount St. Helens, May 18,1980

The tremors began on March 16, 1980. Eleven days later, a first explosion resulted in a 250-foot wide crater on the top of the mountain. Mount St. Helen had awakened and shook the area in warning. Not everyone was listening. Despite the tremors and the initial blast, despite the warnings issued by the authorities, despite the National Guard’s roadblocks, many residents still refused to evacuate the area.

(Aerial pictures of Mt St Helen’s eruption on May 18, 1980, taken by Richard Gordon Bowen)

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Despite the tremors and the initial blast, despite the warnings issued by the authorities, despite the National Guard’s roadblocks, many residents still refused to evacuate the area.

 

5/18/80.  Original photo of the eruption.
5/18/80. Original photo of the eruption.

 

On May 18, 1980, a massive 5.1 magnitude earthquake triggered the most disastrous volcanic eruption in United States history. The high-pressure explosion ripped off the north face of the mountain causing the largest landslide ever recorded while volcanic ash blasted in the air and eventually landed in 11 different states. The eruption and avalanche destroyed the area and killed 57 people.

 

helens_page03 7_22_80 645

7/22/80, 7:02 eruption. Measured height 50,000 feet. The ash cloud was measured by radar in Portland. This boast removed a dome measuring 300×100 feet which had built up in June and July, leaving a large hole.

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5/18/80. Original photo of the eruption. 10:35 am. Closer view from the south. See #10
7/17/80, shot after the eruption.
7/17/80, shot after the eruption.
helens_page03 7_22_80 630
7/22/80, 6:27 eruption., measured height 60,000 feet. The ash cloud was measured by radar in Portland. This boast removed a dome measuring 300×100 feet which had built up in June and July, leaving a large hole. See #20

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