GEOL 114 Lecture Notes - Lecture 12: Igneous Rock, Petrology, Oceanic Crust
Document Summary
The study of how minerals combine is called petrology. Three main categories: igneous: crystalize from a molten state. These rocks can be further classified by the way they cool and crystalize. Extrusive/volcanic: cool and crystallize rapidly at the surface. This process forms small crystals and thick layers of rock: formed by cooling lava of falling of ash after an eruption. This process forms large crystals: form the cores of mountain ranges. Magma flows between these structures and form dikes, sills, and batholiths. Both types of rocks can be classified by the amount of iron and magnesium. Mafic: high levels of mg and fe. Tend to be dense and dark, have a high melting temperature, and low viscosity. Magmas associated with this flow easily: form oceanic crust and continental basaltic flows such as columbia river basalts. Silicic: low levels of mg and fe. Tend to be light in color and have a low melting temperature.
