Fire Mountain: The Eruption and Rebirth of Mount St. Helens
Two hundred and thirty square miles leveled in moments Five hundred and forty million tons of ash and volcanic rock exploded twelve miles high One cubic mile of earth blasted from the crest of one of the world's most beautiful snowcapped domes Captured in rare and spectacular aerial photography and survivor's own words and pictures, witness the terrifying fury of the worst volcanic disaster in American history
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| Stratovolcano Steep, conical volcanoes built by the eruption of viscous lava flows, tephra, and pyroclastic flows, are called stratovolcanoes. Usually constructed over a period of tens to hundreds of thousands of years, stratovolcanoes may erupt a variety of magma types, including basalt, andesite, dacite, and rhyolite. All but basalt commonly generate highly explosive eruptions. A stratovolcano typically consists of many separate vents, some of which may have erupted cinder cones and domes on the volcano's flanks. A synonym is composite cone.  Mount Mageik volcano viewed from the Valley of Ten Thousand Smokes, Katmai National Park and Preserve, Alaska. Mageik's broad summit consists of at least four separate structures built above different vents. |
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Of Earth's 1,511 volcanoes known to have erupted in the past 10,000 years, 699 are stratovolcanoes.
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Earth's highest volcano is a stratovolcano; Nevado Ojos del Salado in Chile is 6,887 m above sea level. The highest volcano with historic eruptions is Llullaillaco, Chile, at 6,739 m. Both volcanoes are located in the northern Chilean Andes.
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Mount St. Helens is the youngest stratovolcano in the Cascades and the most active. Geologists have identified at least 35 layers of tephra erupted by the volcano in the past 3,500 years.
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Mount Shasta is the largest stratovolcano in the Cascades.
Lava Flows and Lava Tubes
40-minute video uses spectacular and unusual footage of erupting volcanoes from Hawaii and around the world to explain the features found in many of our volcanic national parks and monuments, and to show how they form. It presents up-to-date scientific ideas about lava flows: how they move, how they change, and how they create lava tubes
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