GSU GEOL 1122K - Study Guide Chapter 4 Geology Questions (11 pages)

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Study Guide Chapter 4 Geology Questions



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Study Guide Chapter 4 Geology Questions

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Pages:
11
School:
Georgia State University
Course:
Geol 1122k - Introductory Geosciences Ii

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Essentials of Geology 4th edition by Stephen Marshak 2 Chapter 4 Up from the Inferno Magma and Igneous Rocks Introduction PowerPoint slides prepared by Rick Oches Professor of Geology Environmental Sciences Bentley University Waltham Massachusetts 1 Essentials of Geology 4th edition by Stephen Marshak Chapter 4 Up from the Inferno Volcano a vent where molten rock comes out of Earth Example Kilauea Volcano Hawaii Hot 1 200oC lava pools around the volcanic vent Hot syrupy lava runs downhill as a lava flow The lava flow slows loses heat and crusts over Finally the flow stops and cools forming an igneous rock 3 Introduction Igneous rock is formed by cooling from a melt Magma melted rock below ground Lava melted rock once it has reached the surface Igneous rock freezes at high temperatures T 1 100 C 650 C depending on composition There are many types of igneous rock 4 Igneous Rocks Melted rock can cool above or below ground Extrusive igneous rocks cool quickly at the surface Lava flows streams or mounds of cooled melt Pyroclastic debris cooled fragments Volcanic ash fine particles of volcanic glass Volcanic rock fragmented by eruption 5 Igneous Rocks Melted rock can cool above or below ground Intrusive igneous rocks cool out of sight underground Much greater volume than extrusive igneous rocks Cooling rate is slower than for extrusives Large volume magma chambers Smaller volume tabular bodies or columns PowerPoint slides prepared by Rick Oches Professor of Geology Environmental Sciences Bentley University Waltham Massachusetts 2 Essentials of Geology 4th edition by Stephen Marshak 2013 W W Norton Company Chapter 4 Up from the Inferno Magma and Igneous Rocks 6 Why Does Magma Form Magma is not everywhere below Earth s crust Magma only forms in special tectonic settings Partial melting occurs in the crust and upper mantle Melting is caused by pressure release volatile addition heat transfer 7 Causes of Melting Decrease in pressure P decompression The base of the crust is hot enough to melt mantle rock But due to high P the rock doesn t melt Melting will occur if P is decreased P drops when hot rock is carried to shallower depths Mantle plumes Beneath rifts Beneath mid ocean ridges 8 Causes of Melting P drops when hot rock is carried to shallower depths Mantle plumes Beneath rifts Under mid ocean ridges 9 Causes of Melting Addition of volatiles flux melting Volatiles lower the melting T of a hot rock Common volatiles include H2O and CO2 Subduction carries water into the mantle melting rock 10 Causes of Melting Heat transfer melting Rising magma carries mantle heat with it This raises the T in nearby crustal rock which then melts 11 What Is Magma Made Of Magmas have three components solid liquid and gas Solid solidified mineral crystals are carried in the melt Liquid the melt itself is composed of mobile ions Dominantly Si and O lesser Al Ca Fe Mg Na and K Other ions to a lesser extent Different mixes of



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