GEOL 101 Chapter Notes - Chapter 4: Plate Tectonics, Flux Melting, Mantle Plume
Document Summary
Magma is liquid rock (under the earth"s surface. Lava is melt that has erupted from a volcano at the earth"s surface. Magma forms when hot rock in the earth melts. When magma rising from the mantle transfers heat into the crust. During partial melting, only part of the source rock melts to form magma. Silica preferentially goes into the melt, so magmas tend to contain more silica than the rock from which they were derived. The composition of magma reflects the original composition of the rock from which the magma formed and the way the magma evolves. Magma rises from depth because of its buoyancy and because of pressure caused by the weight of overlying rock. Felsic melt is more viscous than mafic melt. Cooler melt is more viscous than hotter melt. Extrusive igneous rocks solidify from lava that erupts out of a volcano. Intrusive igneous rocks develop from magma that freezes inside the earth.
