Axia Week 5 Geology

Topics: Plate tectonics, Earth, Igneous rock Pages: 4 (1129 words) Published: December 3, 2011
Associate Program Material

History of Rock Worksheet

Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of igneous rocks.

| Plate tectonics play a major role in the origin of igneous rocks. Igneous rocks are called fire rocks and are formed either| |underground or above ground. Underground, they are formed when the melted rock, called magma, deep within the earth becomes trapped| |in small pockets. As these pockets of magma cool slowly underground,the magma becomes igneous rocks. Igneous rocks are also formed | |when volcanoes erupt, causing the magma to rise above the earth's surface. When magma appears above the earth, it is called lava. | |Igneous rocks are formed as the lava cools above ground. Rock formed of lava is called extrusive, rock from shallow magma is called| |intrusive and rock from deep magma is called plutonic. Igneous rocks form in three main places. They form where lithospheric plates| |pull apart at mid-ocean ridges, where plates come together at subduction zones and where continental crust is pushed together, | |making it thicker and allowing it to heat to melting. | |Most magmas are associated with plate tectonics. Basaltic and ultramafic magmas form along the divergent mid oceanic ridges and | |are major components of new oceanic crust. More felsic magmas, such as andesites and rhyolites, are associated with the edges of | |continental crust at subduction zones along converging plate boundaries. Whether a magma is intermediate or felsic may depend on | |the relative amounts of oceanic crust and continental crust in the subduction zone that melt to form the magma. The great abundance| |of granitic intrusions in continental crust is thought to be related to the partial melting of the lower continental crust.Plate | |tectonics is the study of how the Earth's plates are driven and shaped by geological...
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