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Volcanoes

Types of volcanic materials GAS: Huge quantitles pour from volcano during eruption. Mostly steam; Includes carbon dloxide, nitrogen and sulfur dloxlde. TEPHRA: Fragments of lava blasted into the air. Sizes range from volcanic dust to volcanic bombs, which can be 4 feet across and weigh 100 tons. Cooled lava flow Central vent Volcanoes | LAVA: Magma that has escaped to Earth's surface. Can be hotter than 2,000 degrees Fahrenheit. Cone . Volcanoes reveal the powerful forces that are continually reshaping the Earth's surface. But new ones aren't commonly found. Now, however, scientists have discovered a mass of magma moving beneath the Mendocino area, 120 miles north of San Francisco. The surging magma may reach the surface in a few years, a few thousand years, or never. Side eruptions are created by secondary conduits Lava flows down the cone, adding to the cone's mass once it cools Side eruption that cooled between older layers of compressed material turns to obsidian. ers of ash and Lay rock from previous eruptions build up the sides of a volcano over time Enormous pressure forces magma to the surface Magma chamber Types of eruptions Types of volcanoes SHIELD Formed when lava flows from a vent and spreads out QUIET ERUPTION Fluid lava streams from side vents, forming a shield volcano. FISSURE Formed when lava comes to the surface through a crack instead of a vent. HOT-ASH ERUPTION Molten rock is violently expelled by gases. Dust and ash settle and form COMPOSITE Formed when lava, dust and rock fragments erupt from vent, piling up in layers Lake Pillshury cinder cone. VIOLENT ERUPTION Magma sometimes plugs the central vent. Pressure builds until magma is blasted into volcanic dust and volcanic bombs. Much of the mountain can be blown apart. surce CİNDER CONES Formed when rock fragments and dust erupt from a vent and settle around it. Potential volcanoes in California Mammoth Mountain Inactive caldera * volcano has growing seismic activity and is releasing carbon diaxide CALDERA Formed when a violent eruption blows off the top of an existing cone. Pockets of moving magma identified by researchers Lake Pillsbury Underground sound sensors have detected magma movement (see left) SOURCES: Dorling Kindersley books, Knight Ridder/Tribune; Union-Tribune research PAUL HORN/Union fribune

Volcanoes

shared by kcatoto on Jan 24
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Volcanoes reveal the powerful forces that are continually reshaping the Earth's surface. But new ones aren't commonly found. Now, however, scientist have discovered a mass of magma moving beneath the ...

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