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Jerry Wilson

on 27 September 2011

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Transcript of Volcanoes

Volcanoes and
Volcanic Landforms A VOLCANO is a cone-shaped mountain produced by magma rising to the surface and forming igneous rock. Beneath every volcano is a MAGMA CHAMBER, a large reservoir of molten rock. One or more vents bring magma from the magma chamber to the surface. Lava is magma that has come to the surface. Lava cools and becomes igneous rock. The CRATER is a large hole at the top of the volcano where lava exits the vent. Some eruptions are explosive, sending large plumes of volcanic ash into the atmosphere. Hot fragments of rock and debris can speed down the slope of the mountain in what is known as a PYROCLASTIC FLOW. Two Kinds of
Lava flows
More common with island volcanoes
Pyroclastic flows
Ash clouds
More common with continental volcanoes
Ash cloud can cause widespread damage. Three Kinds of
Volcanic Cones CINDER CONES are small, cone-shaped volcanoes that are formed from explosive eruptions. TEPHRA is the term for any type of debris thrown off by a volcano, such as:
Ash - Fine, dust-like particles
Cinders - Medium-sized particles of volcanic debris
Bombs - Boulder-sized or larger chunks of debris SHIELD CONES are broad-based, gently-sloping volcanoes formed from the accumulation of lava that has cooled into igneous rock, like basalt. They form from quiet eruptions. They are the largest volcanoes. COMPOSITE CONES are formed by alternating layers of hardened lava and tephra. They form from volcanoes that produce both lava flows and explosive eruptions. Landforms Produced
by Volcanoes BATHOLITH - Mountain-sized hunk of igneous rock underground An exposed batholith mountain. SILL - layer of igneous rock formed as magma squeezes between layers of sedimentary rock. DIKE - layer of igneous rock cutting across other rock layers VOLCANIC NECK - hardened lava inside a volcano's vent Devil's Tower in Wyoming is a volcanic neck. Shield Volcanoes are large and wide and made of lava flows. Composite cones are made of layers of both lava and ash. Is being near an erupting volcano safe? Dike Sill
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