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Mount St. Helens Eruption

May 18, 1980

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Eruption of Mount St Helens
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Mount St. Helens erupted at 8:32 a.m. PST on May 18, 1980, reminding Pacific Northwest residents and people around the world of the powerful and uncontrollable forces of nature. Physical effects of the eruption were experienced in dozens of U.S. states, with ash falling as far away as Oklahoma. Visit Mount St. Helens yourself to learn more about the volcano's history and current condition.

Here is the sequence of events that occurred during the May 18 eruption of Mount St. Helens:

  • A 5.1-magnitude earthquake
  • The bulge and surrounding area on the north face of the volcano slid away, resulting in a huge avalanche of rocks, mud, and debris the filled 24 square miles of valley
  • The resulting release of pressure from within the volcano released a plume of ash and pumice

The impacts of the 1980 eruption of Mount St. Helens included:

  • Mount St. Helens was reduced by over 1,300 feet in height
  • Volcanic ash fell as far as 930 miles away (see ash fall map)
  • The debris avalanche and mudflows buried the Toutle valley to a depth of almost 50 meters
  • The eruption lasted for 9 hours
  • 57 people lost their lives, or are still considered missing
  • 250 square miles of land was damaged
  • "Countless" animals were killed - estimates are 7,000 big game animals and millions of birds, fish, and small mammals
  • Minor eruptions continued into 1986

View a 1980 Satellite Photo of Blast Zone.

Facts and figures obtained from USGS summary

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