Basic Geology/Glossary

This is an incomplete list of geological terminology with brief explanations of each concept. Andesite: Viscous lava erupted from a volcano above a subduction zone. Igneous Rock: A rock produced by the crystallization of magma. Geology: The study of Earth's physical structure and the processes that act on it. Lahar: River of mud, ash, and water. Metamorphic Rock: A rock that has experienced intense temperature and/or pressure after its formation and has changed its composition and/or texture. Mineral: A naturally occurring solid inorganic substance with a distinct crystal structure. Pahoehoe: Lava with an undulating surface, may have a ropey appearance. Rift Valley: A gap between the continental crust marked by volcanism; rift valleys may eventually develop into oceans, seas, etc. Rock: A natural material composed of minerals. Sedimentary Rock: A rock that has been formed by the lithification of sediment but has not been metamorphosed. Subduction zone: Area where plates meet, and one slides beneath the other. Texture: The physical appearance of a rock.