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   Mount St. Helens

   Roughly 700 years of dormancy were broken in about 1480, when large amounts of pale gray dacite pumice and ash started to erupt, beginning the Kalama period. ... Mount St. Helens erupted on May 18, 1980, at 08:32 a.m. Pacific Daylight Time
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   1980 eruption of Mount St. Helens

   The 1980 eruption of Mount St. Helens, a stratovolcano located in Washington state, in the United States, was a major volcanic eruption.
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   The Eruption of Mount St. Helens!

   1980 eruption of Mount St. Helens
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   Mount St. Helens National Volcanic Monument

   It was established on August 27, 1982 by U.S. President Ronald Reagan following the 1980 eruption of Mount St. Helens.
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   Washington State Route 504

   On May 18, 1980, Mount St. Helens erupted after two months of small earthquakes and pre-avalanche eruptions.
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   2004–2008 volcanic activity of Mount St. Helens

   The new dome did not rise above the caldera created by the 1980 eruption of Mount St. Helens.
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   1980 in the United States

   Mount St. Helens erupts on May 18 in Washington state, killing 57 people
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   Cascade Volcanoes

   When Cascade volcanoes do erupt, pyroclastic flows, lava flows, and landslides can devastate areas 10 or more miles away; and huge mudflows of volcanic ash and debris, called lahars, can inundate valleys more than 50 miles (80 km) downstream. ... 1980 Eruption of Mount St. Helens
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   Geology of the Pacific Northwest

   Mount St. Helens erupts on May 18, 1980 ... This newly formed magma rises toward the Earth's surface to erupt, forming a chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone.
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    Prediction of volcanic activity

    Mount St. Helens erupted explosively on May 18, 1980 at 8:32 a.m. PDT ... Since he knew that these two volcanoes were connected by a small fissure, he knew that Mt. Nyiragongo would erupt soon.

Explore the following pages on Powerset:

• Mount St. Helens,
• 1980 eruption of Mount St. Helens,
• The Eruption of Mount St. Helens!,
• Mount St. Helens National Volcanic Monument,
• Washington State Route 504,
• 2004–2008 volcanic activity of Mount St. Helens,
• 1980 in the United States,
• Cascade Volcanoes,
• Geology of the Pacific Northwest,
• Prediction of volcanic activity

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