How old is Mount St. Helens?
The eruptive history of Mount St. Helens began about 40,000 years ago with dacitic volcanism, which continued intermittently until about 2,500 years ago. This activity included numerous explosive eruptions over periods of hundreds to thousands of years, which were separated by apparent dormant intervals ranging in length from a few hundred to about 15,000 years.
The range of rock types erupted by the volcano changed about 2,500 years ago. Since then, Mount St. Helens repeatedly has produced lava flows of andesite, and produced basalt on at least two occasions. Other eruptions during the last 2,500 years produced: dacite and andesite pyroclastic flows and lahars as well as dacite, andesite, and basalt airfall tephra. Major intervals of dormancy over the last 2,500 years range in length from about 200 to 700 years.
Learn more: USGS Cascades Volcano Observatory
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Will extinct volcanoes on the east coast of the U.S. erupt again?
No. The geologic forces that generated volcanoes in the eastern United States millions of years ago no longer exist. Through plate tectonics, the eastern U.S. has been isolated from the global tectonic features (tectonic plate boundaries and hot spots in the mantle), that cause volcanic activity. So new volcanic activity is not possible now or in the near future. If you wait around several hundred...
Eruptions of Mount St. Helens : past, present, and future
Mount St. Helens - From the 1980 eruption to 2000
Volcanic-hazard zonation for Mount St. Helens, Washington, 1995
Road guide to volcanic deposits of Mount St. Helens and vicinity, Washington
The 1980 eruptions of Mount St. Helens, Washington
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- FAQ
Will extinct volcanoes on the east coast of the U.S. erupt again?
No. The geologic forces that generated volcanoes in the eastern United States millions of years ago no longer exist. Through plate tectonics, the eastern U.S. has been isolated from the global tectonic features (tectonic plate boundaries and hot spots in the mantle), that cause volcanic activity. So new volcanic activity is not possible now or in the near future. If you wait around several hundred...
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Filter Total Items: 17
Eruptions of Mount St. Helens : past, present, and future
No abstract available.AuthorsRobert I. Tilling, Lyn J. Topinka, Donald A. SwansonMount St. Helens - From the 1980 eruption to 2000
Mount St. Helens, Washington, is the most active volcano in the Cascade Range. Its most recent series of eruptions began in 1980 when a large landslide and powerful explosive eruption created a large crater, and ended 6 years later after more than a dozen extrusions of lava built a dome in the crater. Larger, longer lasting eruptions have occurred in the volcano's past and are likely to occur in tAuthorsSteve Brantley, Bobbie MyersVolcanic-hazard zonation for Mount St. Helens, Washington, 1995
No abstract available.AuthorsE.W. Wolfe, T. C. PiersonRoad guide to volcanic deposits of Mount St. Helens and vicinity, Washington
Mount St. Helens, the most recently active and most intensively studied Cascades volcano, is in southwestern Washington. The volcano is a superb outdoor laboratory for studying volcanic processes, deposits of observed events, and deposits whose origins are inferred by classic geologic techniques, including analogy to recent deposits. During the past 4,500 years, Mount St. Helens has been more actiAuthorsMichael P. DoukasThe 1980 eruptions of Mount St. Helens, Washington
No abstract available.AuthorsPeter W. Lipman, Donal Ray Mullineaux - News