Igneous petrology
Igneous petrology is the study of rocks formed when magma or lava cools and solidifies, including their origins, composition, and evolution.
Igneous rock: A rock formed by the cooling and solidification of magma or lava. This is the rock family that igneous petrology investigates.
Fractional crystallization: The separation of early-formed crystals from a melt as crystallization proceeds. Removing crystals changes the residual magma and can produce evolved igneous rocks.
QAPF diagram: A classification diagram for many plutonic rocks based on quartz, alkali feldspar, plagioclase, and feldspathoids. It assigns systematic names to coarse-grained rocks using their modal mineral proportions.
James Hutton: An eighteenth-century Scottish geologist whose work helped establish geology as a historical science. His observations of intrusive rocks supported explanations based on processes operating within Earth.
Metamorphic petrology: The study of rocks transformed by heat, pressure, and chemically active fluids without complete melting. It examines solid-state changes rather than crystallization from magma or lava.
Magma: Molten or partly molten rock beneath Earth's surface, commonly containing crystals and dissolved gases. Its composition and evolution shape the igneous rocks it produces.
Partial melting: The melting of only some minerals in a rock, producing a melt compositionally distinct from its source. Different degrees of melting help explain variation among primary magmas.
TAS diagram: A diagram that classifies volcanic rocks by total alkalis and silica content. It provides names for fine-grained volcanic rocks when mineral modes are difficult to determine.
Norman L. Bowen: A Canadian geologist known for experimental studies of silicate melts and mineral crystallization. His experiments established a framework for interpreting crystallization and magma differentiation.
Sedimentary petrology: The study of sediments and sedimentary rocks, including their formation, composition, and alteration. Its rocks form through deposition and lithification rather than magma solidification.