VOLCANISM

VOLCANISM - VOLCANISM The processes by which magma and...

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VOLCANISM * The processes by which magma and gases are transferred from the Earth’s interior to near or on the surface. * 2 basic types: extrusive vs intrusive volcanism Extrusive: when magma (lava) flows out onto the Earth’s surface and then cools to form igneous rocks. * volcano: a landform with a vent, or fissure(crack) on the surface which is the end of a conduit originating from below the crust in the Asthenosphere * often a mountain landform (fissures usually do not form features of high relief) * magma originating in the Asthenosphere is expelled through the conduit & out the vent * magma originating in the Asthenosphere is expelled through the conduit and out the vent * crater: the surface depression at the summit of the volcano * a volcano may be categorized as Active: currently erupting, or has erupted during recorded history Dormant : an active volcano that is in repose but is expected to erupt in the future
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Extinct : a volcano that is not expected to erupt again * 75% of volcanoes are on the sea floor * most convergent and divergent plate boundaries have high volcanic activity * Hot spots are also areas of high volcanic and earthquake activity * lava : the molten rock issued from a volcano; the term used for magma once it has erupted onto the Earth’s surface * may be two types of material: mafic or felsic * mafic or basaltic lava : high in Mg & Fe, < 50% silica thus less viscous which means it flows readily, and thus less gas is trapped within leading to a less explosive eruption * felsic : richer in silica thus more viscous meaning it flows slower: it is also more acidic, and more gases are trapped leading to more explosive eruptions
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This note was uploaded on 07/10/2011 for the course GEOG 1101 taught by Professor Connor during the Spring '08 term at UGA.

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VOLCANISM - VOLCANISM The processes by which magma and...

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