GLG 301 Lecture Notes - Lecture 3: Continental Crust, Oceanic Crust, Metamorphic Rock
Document Summary
Rocks are naturally-occurring aggregates of minerals (and by definition glass and coal) They are generally classified by: how they formed. Chemical composition texture (grain or crystal size) Texture and composition can tell us a lot about the history of the rock. Formed from the cooling of molten rock (magma) either on or below the surface of the earth. Magmas form (rocks melt) if one or more of the following occurs: Increase temperature past melting point of specific minerals. Usually by bringing hotter material (or magma) up into cooler areas. Melting of only some minerals is called partial melting: decrease pressure. Decompression by rising hot mantle rock (plumes) Decompression beneath rifts and mid-ocean ridges: add volatiles (especially water) In particular water is brought to depth in the process of subduction. As they cool, the minerals can react with the remaining melt and change into new minerals: differentiation.
