CSET Earth & Space Sciences (219) key terms

The long stable stage of a star's life when hydrogen fuses into helium in its core, balancing gravity; the Sun and most stars spend most of their lives here.

A graph plotting stars by luminosity against temperature or spectral class; it reveals that most stars fall along a diagonal band and helps classify stellar life stages.

The process in which light atomic nuclei join to form heavier ones, releasing energy; it powers stars and converts hydrogen to helium in stellar cores.

An evolved star that has swollen and cooled after exhausting core hydrogen, becoming large and reddish; a late stage for medium-mass stars like the Sun.

The dense, Earth-sized remnant left when a medium-mass star sheds its outer layers; it no longer fuses fuel and slowly cools over billions of years.

A catastrophic stellar explosion that can outshine an entire galaxy; it occurs when a massive star collapses or a white dwarf gains too much mass, scattering heavy elements.

The leading model explaining that the Solar System formed from a rotating cloud of gas and dust that collapsed under gravity into a disk, with the Sun at its center.

A small body of rock and ice, kilometers across, formed by collisions of dust in the early solar disk; planetesimals merged to build planets.

The gradual buildup of larger bodies by the collision and sticking together of smaller particles, planetesimals, or gas; the process that assembled the planets.

Three rules describing orbits: planets travel on ellipses with the Sun at one focus, sweep equal areas in equal times, and have periods squared proportional to orbital radius cubed.

A number describing how stretched an orbit is, from 0 for a perfect circle toward 1 for a highly elongated ellipse; it measures orbital shape, not size.

The time a body takes to complete one revolution around another; for planets it increases with distance from the Sun according to Kepler's third law.

A small, dense, rocky planet with a solid surface and thin atmosphere, like Mercury, Venus, Earth, and Mars; formed close to the Sun where it was too hot for ices.

A large, low-density gas or ice giant such as Jupiter, Saturn, Uranus, or Neptune, with thick atmospheres and no solid surface; formed farther out where ices persisted.

The total amount of energy a star emits per unit time, often compared to the Sun; it depends on stellar size and surface temperature.

The theory that Earth's rigid outer shell is broken into plates that move over the mantle, causing earthquakes, volcanoes, mountain building, and continental drift.

A convergent boundary where one tectonic plate descends beneath another into the mantle, producing deep ocean trenches, earthquakes, and volcanic arcs.

A boundary where tectonic plates move apart and new crust forms from upwelling magma; examples include mid-ocean ridges and continental rift valleys.

A boundary where two tectonic plates collide, causing subduction or continental collision; it builds mountains and generates powerful earthquakes.

The process at mid-ocean ridges where magma rises, solidifies, and pushes older oceanic crust outward on both sides, creating new seafloor and recording magnetic reversals.

A naturally occurring, inorganic solid with a definite chemical composition and ordered atomic structure; minerals are the building blocks of rocks.

Rock formed when molten material cools and solidifies; slow cooling underground makes coarse crystals, while rapid cooling at the surface makes fine ones.

Rock formed from compacted and cemented sediments or from chemical precipitation; layers called strata often preserve fossils and record past environments.

Rock changed by heat, pressure, or chemically active fluids while remaining solid; foliation and recrystallization are common signs of metamorphism.

A relative ranking from 1 (talc) to 10 (diamond) of how easily minerals are scratched; a harder mineral scratches a softer one, aiding identification.

The breakdown of rocks and minerals at or near Earth's surface by physical, chemical, or biological processes; it produces sediment without transporting it.

The removal and transport of weathered material by water, wind, ice, or gravity; it shapes landforms and moves sediment toward depositional basins.

The laying down of sediment when transporting agents lose energy, such as a river slowing or a glacier melting; deposited layers may later become sedimentary rock.

The ongoing set of processes that transform rock among igneous, sedimentary, and metamorphic types through melting, cooling, weathering, burial, and deformation.

The warming of a planet's surface as atmospheric gases absorb and re-emit outgoing infrared radiation; it keeps Earth habitable but intensifies with added greenhouse gases.

The fraction of incoming solar radiation reflected by a surface; bright surfaces like ice and clouds have high albedo, dark surfaces absorb more energy.

Heat transfer by the movement of fluid; warm, less dense material rises while cooler, denser material sinks, driving winds, ocean currents, and mantle motion.

The apparent deflection of moving air or water due to Earth's rotation; it turns motion to the right in the Northern Hemisphere and left in the Southern Hemisphere.

The global deep-ocean conveyor driven by differences in temperature and salinity; cold, salty water sinks and drives slow currents that redistribute heat worldwide.

The amount of dissolved salts in water, usually expressed in parts per thousand; it affects density and helps drive deep ocean circulation.

The continuous movement of water among oceans, atmosphere, land, and living things through evaporation, condensation, precipitation, runoff, and infiltration.

The change of liquid water into vapor, taking up energy; it drives the water cycle and cools the surface from which water leaves.

Water falling from clouds to the surface as rain, snow, sleet, or hail; it returns atmospheric moisture to the land and oceans.

Determining the order of past events without assigning numerical ages, using principles such as superposition and cross-cutting relationships.

The principle that in undisturbed sedimentary layers, each layer is older than the one above it and younger than the one below.

Estimating the numerical age of a sample by measuring the ratio of a radioactive parent isotope to its decay product, given the isotope's known half-life.

The time required for half the atoms of a radioactive isotope to decay; it provides the clock used in radiometric dating of rocks and fossils.

A fossil of a species that lived over a short time span but across a wide area, allowing geologists to correlate and date rock layers in different places.

Preserved evidence of past life, such as bones, shells, impressions, or traces; fossils are most common in sedimentary rocks and document evolution and past environments.

The process by which individuals with inherited traits better suited to their environment survive and reproduce more, shifting the traits of populations over generations.

An inherited feature or behavior that improves an organism's ability to survive and reproduce in its environment; it arises through natural selection over generations.

A geologically brief event in which a large share of species dies out worldwide, such as the end-Permian and end-Cretaceous events, reshaping ecosystems.

The calendar of Earth history dividing time into eons, eras, periods, and epochs based on major events and fossil changes recorded in rocks.

A gap in the rock record where layers were eroded away or where deposition paused before younger layers formed; it marks missing time.

A persistent, intuitive idea that conflicts with accepted scientific understanding, such as the belief that seasons result from Earth's changing distance from the Sun.

Teaching that engages students in asking questions, planning investigations, gathering and analyzing data, and constructing evidence-based explanations rather than memorizing facts.

Ongoing checks of student understanding during instruction, used to adjust teaching and give feedback rather than to assign a final grade.

A simplified representation of a system or process used to explain observations and make predictions; models are revised as evidence accumulates.