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Volcano's Deadly Warning. Volcanoes Online. National Geographic: Eye in the Sky. Volcanoes are awesome manifestations of the fiery power contained deep within the Earth.

National Geographic: Eye in the Sky

These formations are essentially vents on the Earth's surface where molten rock, debris, and gases from the planet's interior are emitted. When thick magma and large amounts of gas build up under the surface, eruptions can be explosive, expelling lava, rocks and ash into the air. Less gas and more viscous magma usually mean a less dramatic eruption, often causing streams of lava to ooze from the vent. The mountain-like mounds that we associate with volcanoes are what remain after the material spewed during eruptions has collected and hardened around the vent. This can happen over a period of weeks or many millions of years. A large eruption can be extremely dangerous for people living near a volcano. Volcanoes tend to exist along the edges between tectonic plates, massive rock slabs that make up Earth's surface. Volcanoes - Introduction.

Volcano Live, John Seach. Volcano Hazards Program. Volcano Field Trip. Volcanoes can be exciting and dangerous.

Volcano Field Trip

They are also educational since they tell us a lot about the earth and even other planets. The inside of the Earth is very hot. Sometimes, this heat melts through the rock of the earth's crust, sending hot liquid rock (called magma) and gases onto the Earth's surface. A buildup of lava and ash around the area of an eruption becomes a volcano. Volcanoes can erupt for a very brief time or they can erupt many times over millions of years.

Concepts How are volcanoes formed? Terms To Learn. Terrestrial Volcanoes. Terrestrial Volcanoes By turns hot embers from her entrails fly, And flakes of mountain flame that arch the sky.

Terrestrial Volcanoes

-Virgil's Aeneid. SAVAGE EARTH Online. Please note: SAVAGE EARTH ONLINE looks best when viewed using Netscape 3.0 or above, or Internet Explorer 3.0 or above, on Macintosh, Windows 95 or Windows 3.1.

SAVAGE EARTH Online

If you have an earlier version, or another browser, all pages may not be presented exactly as designed. To view the animations in SAVAGE EARTH ONLINE, you will need the free Flash plug-in. Premiere: July 19, 1998, at 8 pm (ET) on PBS. (Watch for repeat showings on your local PBS station.) A Study of Plate Tectonics. Mount St Helens. Feature Pictured is the ash-and-gas plume produced during the plinian phase of the climactic eruption of Mount St. Helens that began shortly after 8:32 a.m. Mount St. Helens - May 18, 1980. Seismogram from station CPW, 112 km (70 mi) northwest of Mount St.

Mount St. Helens - May 18, 1980

Helens, May 18, 1980 Summary of Events. Mount St. Helens National Volcanic Monument. Fireweed, growing in Mount St.

Mount St. Helens National Volcanic Monument

Helens' devastated area; view from the north. Summer 1984. The Mount St. Helens National Volcanic Monument is within the Gifford Pinchot National Forest and managed by the USDA Forest Service. The Monument was established in 1982 to designate 445 km2 (110,000 acres) around Mount St Helens for research, recreation, and education. The Monument offers many seasonal activities such as hiking, camping, fishing, snow sport, and ranger led educational programs. Mauna Loa, Decade Volcano. How Volcanoes Work. Global Volcanism Program: Worldwide Ho. Mount Saint Helens. Cascades Volcano Observatory (CVO) Mh Overlay represents area within CVO's area of responsibility.

Cascades Volcano Observatory (CVO)

Students Explore Fluvial Sediment Sampling Techniques in Training Course Near Mount St. HelensApril 10, 2014 CVO staff and sediment specialists from USGS offices around the country led the Sediment Data Collection Techniques training course in Castle Rock, Washington. The week-long course was attended by 30 students representing the USGS, U.S. Natural Hazards Explained: New Article Describes Behavior of Debris FlowsMarch 31, 2014 Over the past half-century, great advances have been made in understanding debris flow behavior.

Quick LinksPhoto ArchiveHot Stuff ArchiveMaps and GraphicsFrequently Asked QuestionsGlossaryPublicationsHydrologyLegacy CVO Home Page. Volcano's Deadly Warning. By Lexi Krock Posted 11.12.02 NOVA What's the difference between lava and magma?

Volcano's Deadly Warning

What are volcanic vents, dikes, and fissures? In this anatomy of a volcano, explore the basic geological features of a volcano such as Mt. The 3 basic rock types. Ask GeoMan...

The 3 basic rock types

What are the 3 basic types of rocks? Just as any person can be put into one of two main categories of human being, all rocks can be put into one of three fundamentally different types of rocks. They are as follows: Igneous Rocks Igneous rocks are crystalline solids which form directly from the cooling of magma. This is an exothermic process (it loses heat) and involves a phase change from the liquid to the solid state. Sedimentary Rocks In most places on the surface, the igneous rocks which make up the majority of the crust are covered by a thin veneer of loose sediment, and the rock which is made as layers of this debris get compacted and cemented together.

Clastic: your basic sedimentary rock. Click here for more on sedimentary processes and rocks (RCC). Metamorphic Rocks The metamorphics get their name from "meta" (change) and "morph" (form). Click here to ask GeoMan a question Return to Ask GeoMan's Index of Questions Return to GeoMan's Home Page.