GL101 Chapter Notes - Chapter 3: Silicate Minerals, Igneous Textures, Continental Crust
Igneous rocks: most igneous rock activity occurs at divergent plate boundaries. Igneous rocks: form from molten rock material, cools and solidifies, parent material is magma. Forms from partial melting of rocks inside earth. Magma that reaches the surface is called lava. Extrusive igneous rocks: form when magma solidifies at the surface, also called volcanic rocks. Intrusive igneous rocks: most igneous rocks are from this type, form at depth from magma that crystallizes slowly, also called plutonic rocks, a body of plutonic rock is called a pluton. Generating magma from solid rock: role of heat. Geothermal gradient: change in temperature with depth. Rocks in lower crust and upper mantle are near their melting points. Bulk of magma forms without additional heat. Melting beings if confining pressure drops or it volatiles (fluid, gases) are introduced: role of pressure. Melting occurs at higher temperatures at depth due to higher confining pressure. When confining pressures drop, decompression melting occurs: role of volatiles.