where is mount st helens?
Skamania County Washington
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 Mount St. Helens or Louwala @-@ Clough ( known as Lawetlat 'la to the indigenous Cowlitz people , and Loowit to the Klickitat ) is an active stratovolcano located in Skamania County , Washington , in the Pacific Northwest region of the United States . It is 96 miles ( 154 km ) south of Seattle , Washington , and 50 miles ( 80 km ) northeast of Portland , Oregon . Mount St. Helens takes its English name from the British diplomat Lord St Helens , a friend of explorer George Vancouver who made a survey of the area in the late 18th century . The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc , a segment of the Pacific Ring of Fire that includes over 160 active volcanoes . This volcano is well known for its ash explosions and pyroclastic flows . 

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 Mount St. Helens , which exhibited phreatic activity just prior to its catastrophic 1980 eruption ( which was itself Plinian ) . 

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 Mount St. Helens is 34 miles ( 55 km ) west of Mount Adams , in the western part of the Cascade Range . These " sister and brother " volcanic mountains are approximately 50 miles ( 80 km ) from Mount Rainier , the highest of Cascade volcanoes . Mount Hood , the nearest major volcanic peak in Oregon , is 60 miles ( 100 km ) southeast of Mount St. Helens . 

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 Two years after the eruption , the United States government set aside 110 @,@ 000 acres ( 450 km2 ) of land for the Mount St. Helens National Volcanic Monument . This protected area , which includes the Johnston Ridge Observatory and several other research and visitor centers , serves as an area for scientific research , tourism , and education . 

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 The 1980 eruption of Mount St. Helens in Washington , which ripped apart the volcano 's summit , was a Plinian eruption of Volcanic Explosivity Index ( VEI ) 5 . 
