FTCE Earth/Space Science 008 key terms

The set of processes that transform material among igneous, sedimentary, and metamorphic rock, driven by melting, weathering, erosion, deposition, compaction, and heat and pressure.

Rock formed when molten material cools and solidifies; slow cooling underground produces large crystals, while rapid cooling at the surface produces fine-grained or glassy textures.

An experimentally derived sequence describing the order in which silicate minerals crystallize from cooling magma, from olivine and calcium-rich plagioclase to quartz and potassium feldspar.

Incomplete melting of rock, usually at depth, that yields magma enriched in silica relative to the source rock because minerals melt at different temperatures.

The process by which a cooling magma body changes composition through crystal settling, partial melting, or mixing, producing a range of rock types from one parent magma.

Rock formed from deposited sediment or from dissolved ions, typically in horizontal layers, and the main archive for fossils and past surface environments.

The compaction and cementation of loose sediment into solid sedimentary rock after burial.

Low-temperature physical and chemical changes that alter sediment after deposition and during burial, including compaction, cementation, recrystallization, and replacement, short of metamorphism.

Solid-state recrystallization of rock in response to changed temperature, pressure, or fluid chemistry, producing new minerals and textures without melting the rock.

A planar layering or alignment of platy or elongate minerals in metamorphic rock, produced by directed pressure and useful for ranking metamorphic grade.

A mineral whose first appearance in a metamorphic rock marks a particular temperature and pressure condition, allowing geologists to map metamorphic grade zones.

In-place breakdown of rock by physical, chemical, or biological processes, producing regolith and dissolved ions without transporting the material away.

The detachment and removal of weathered material by moving water, wind, ice, or gravity, the step that precedes transport and deposition of sediment.

A setting, such as a river channel, beach, reef, or deep sea floor, whose energy and chemistry determine the texture, sorting, and structures of accumulating sediment.

The unifying theory that the lithosphere is divided into rigid plates that move over the asthenosphere, generating earthquakes, volcanoes, mountains, and ocean basins at their boundaries.

A plate margin where lithosphere pulls apart, creating new crust through seafloor spreading or continental rifting, accompanied by shallow earthquakes and basaltic volcanism.

A convergent margin where denser oceanic lithosphere descends beneath another plate, producing deep earthquakes, volcanic arcs, and trenches.

Creation of new oceanic crust at mid-ocean ridges as magma rises and cools, then moves laterally away from the ridge, recording magnetic reversals in symmetric stripes.

A dipping plane of earthquake foci that extends from a trench to depths near 700 kilometers and traces the descent of a subducting slab.

The condition in which rigid lithosphere floats in gravitational balance on the denser mantle, so that thick or low-density crust stands higher and adjusts as loads are added or removed.

Elastic energy traveling through Earth; P waves are compressional and fastest, S waves are shear waves that cannot pass liquids, and surface waves cause most structural damage.

The boundary between Earth's crust and mantle, identified by an abrupt increase in seismic wave velocity at roughly 5 to 70 kilometers depth.

The point within the crust or mantle where fault rupture begins and seismic energy is released; the surface point directly above it is the epicenter.

A fracture along which rock has moved, classified as normal, reverse, or strike-slip according to the direction of slip and the stress regime that produced it.

The principle that in an undisturbed sequence of layered sedimentary rock, each layer is younger than the one below it and older than the one above.

Establishing the order of geologic events without numerical ages, using superposition, cross-cutting relationships, inclusions, and fossil succession.

A fossil species that existed for a short interval but was geographically widespread, allowing rocks in different regions to be correlated to the same time span.

Correlation of rock layers using their contained fossils, based on the principle that fossil assemblages succeed one another in a consistent order.

A surface representing missing time in the rock record, formed by erosion or nondeposition and recognizable where younger strata overlie older eroded or folded rocks.

Determining the numerical age of a material from the measured ratio of parent to daughter isotopes and the known decay constant of the parent isotope.

The time required for half of the radioactive parent atoms in a sample to decay into daughter products; it is constant for each isotope and independent of temperature and pressure.

An atom of an element with the same number of protons but a different number of neutrons; unstable isotopes decay and are used as geologic clocks and environmental tracers.

A geologically rapid loss of a large share of species, recorded in the fossil record and commonly linked to asteroid impact, flood volcanism, or rapid climate and ocean change.

The hierarchical division of Earth history into eons, eras, periods, and epochs, with boundaries placed at major changes in the fossil record and radiometrically dated.

The model in which the solar system formed from a rotating cloud of gas and dust that collapsed, flattened into a disk, and accreted into a central star and orbiting planets.

The growth of larger bodies by collision and sticking together of smaller particles and planetesimals in the early solar nebula.

A kilometer-scale solid body formed in the protoplanetary disk whose collisions built the planets and whose fragments survive as asteroids and meteorites.

Three statements describing orbital motion: orbits are ellipses with the Sun at one focus, equal areas are swept in equal times, and orbital period squared is proportional to semimajor axis cubed.

The rule that gravitational attraction between two masses is proportional to their product and inversely proportional to the square of the distance between them, explaining orbits and tides.

A number from zero to one describing how much an orbit departs from a circle; zero is circular and values near one are highly elongated ellipses.

The full range of electromagnetic radiation ordered by wavelength and energy, from gamma rays through visible light to radio waves, each band revealing different physical processes.

The shift in observed wavelength caused by relative motion between source and observer; redshift indicates recession and blueshift indicates approach.

A measure of a star's intrinsic brightness defined as its apparent magnitude if it were placed at a standard distance of 10 parsecs.

A plot of stellar luminosity against temperature or spectral class that reveals the main sequence, giants, supergiants, and white dwarfs and serves as a tool for studying stellar evolution.

The long-lived stage in which a star fuses hydrogen to helium in its core; the Sun and most stars fall along this diagonal band on the Hertzsprung-Russell diagram.

Formation of chemical elements by nuclear reactions, occurring in the Big Bang, in stellar cores, and in supernova explosions that disperse heavy elements into space.

The explosive end of certain massive stars or accreting white dwarfs, which briefly outshines a galaxy and disperses newly formed heavy elements into the interstellar medium.

The observation that distant galaxies recede at speeds proportional to their distance, implying an expanding universe and providing a way to estimate cosmic distances and age.

The model in which the universe began in a hot, dense state and has expanded and cooled since, supported by cosmic expansion, the microwave background, and primordial element abundances.

A distance unit equal to about 3.26 light-years, defined as the distance at which one astronomical unit subtends an angle of one arcsecond.

The distance light travels in vacuum in one year, about 9.46 trillion kilometers, used to express interstellar and intergalactic distances.

The periodic rise and fall of sea level caused mainly by the Moon's and Sun's gravitational pull, modified by coastline shape, water depth, and Earth's rotation.

The amount of solar radiation reaching a given area of Earth's surface, varying with latitude, season, and axial tilt and driving atmospheric and ocean circulation.

The fraction of incoming solar radiation reflected by a surface; ice and clouds have high values and dark oceans low values, so albedo changes feed back into climate.

Warming of a planet's surface because atmospheric gases absorb and re-emit outgoing infrared radiation, raising surface temperature above the value expected without an atmosphere.

The apparent deflection of moving air or water to the right in the Northern Hemisphere and left in the Southern Hemisphere because of Earth's rotation.

The exchange of carbon among the atmosphere, oceans, biosphere, soils, and rocks through photosynthesis, respiration, dissolution, burial, and combustion over varied timescales.

The record of Earth's past magnetic field direction and intensity preserved in magnetic minerals in rocks, used to document seafloor spreading and continental drift.

The thicker, less dense, granitic portion of Earth's crust that stands above sea level in isostatic balance and is too buoyant to subduct readily.

A simplified representation of a natural system used to explain observations and make testable predictions, always subject to revision as evidence accumulates.