New Zealand Scholarship Earth and Space Science key terms

The gravitational balance in which buoyant lithosphere floats on the denser mantle, so thicker or less dense crust rides higher, and loading or erosion causes vertical adjustment until equilibrium is restored.

The rigid outer shell of a planet comprising the crust and uppermost mantle, broken into tectonic plates that translate, rotate and deform above the weaker asthenosphere.

Slow circulation of hot rock driven by heating from below and cooling from above, transporting heat outward and providing the main force that moves tectonic plates across Earth's surface.

A zone where two lithospheric plates meet, classified as divergent, convergent or transform depending on relative motion, and marked by characteristic earthquakes, volcanism and topography.

The sinking of dense oceanic lithosphere beneath another plate at a convergent boundary, generating deep earthquakes, arc volcanism, trenches and recycling of crust into the mantle.

A naturally occurring, inorganic solid with a definite chemical composition and an ordered internal atomic structure, identified by properties such as hardness, cleavage, lustre and crystal form.

Rock formed by cooling and crystallisation of molten material, either slowly underground producing coarse grains or rapidly at the surface producing fine grains or glass.

Solid-state recrystallisation of existing rock in response to changed temperature, pressure or fluid conditions, producing new mineral assemblages and fabrics without melting the bulk rock.

Incomplete fusion of rock in which only the lowest-melting components liquefy, producing magma of different composition from its source and driving chemical differentiation of the crust.

Separation of early-formed crystals from remaining melt, progressively changing magma composition toward silica-rich, lower-temperature liquids and explaining compositional variation among igneous rocks.

The use of mineral compositions and equilibria preserved in rocks to estimate the temperature and pressure at which they formed, allowing reconstruction of burial and exhumation histories.

Age determination from the measured ratio of parent to daughter isotopes in a sample, combined with a known decay constant, giving absolute ages for minerals and rocks.

The time required for half the radioactive atoms in a sample to decay, a fixed property of each isotope that sets the useful age range of a dating method.

The internationally agreed subdivision of Earth history into eons, eras, periods and epochs, calibrated by radiometric ages and defined by characteristic fossils and events.

Correlation of rock layers using their contained fossils, especially short-ranging index species, allowing relative ages to be established between separated sequences.

The study of processes affecting organisms after death, including decay, transport, burial and mineralisation, which determine whether and how fossils enter the rock record.

A geologically rapid loss of a large proportion of species across many habitats, recorded by abrupt changes in fossil assemblages and often linked to volcanism, impacts or climate shifts.

The description and interpretation of layered rocks, applying superposition, original horizontality and cross-cutting relationships to establish sequences and relative timing of geological events.

The exchange of carbon among atmosphere, ocean, biosphere, soils and rocks through photosynthesis, respiration, weathering, burial and volcanism, operating over timescales from hours to millions of years.

The fraction of incoming solar radiation reflected by a surface or planet, influencing energy balance; ice and cloud changes alter albedo and can amplify or damp climate change.

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

The change in net energy flux at the top of the atmosphere caused by a factor such as greenhouse gases, aerosols or solar variation, expressed in watts per square metre.

Large-scale overturning of the ocean driven by differences in temperature and salinity, which set density and control sinking of cold salty water and slow upwelling elsewhere.

Deflection of moving fluids and objects caused by planetary rotation, to the right in the Northern Hemisphere and left in the Southern, shaping winds, currents and storm rotation.

The ocean depth below which carbonate minerals dissolve faster than they accumulate, so seafloor sediment lacks calcium carbonate; its position tracks ocean chemistry and climate.

Discrete wavelengths absorbed or emitted by atoms and ions as electrons change energy levels, providing a diagnostic fingerprint of composition, temperature and motion of distant matter.

Change in observed wavelength caused by relative motion between source and observer; redshift indicates recession and blueshift approach, enabling measurement of stellar and galactic velocities.

A plot of stellar luminosity against temperature or spectral class revealing main sequence, giants, supergiants and white dwarfs, and providing the framework for stellar evolution.

Formation of chemical elements by nuclear fusion inside stars and in supernova explosions, accounting for the abundances of elements heavier than helium in planets and living things.

The observed proportionality between a galaxy's recession velocity and its distance, implying an expanding universe and providing the basis for estimating cosmic distances and age.

Faint, nearly uniform microwave radiation from the early universe, whose tiny temperature fluctuations record density variations that seeded galaxy formation.

Three empirical rules describing planetary orbits as ellipses with the Sun at one focus, sweeping equal areas in equal times, and having period squared proportional to orbital radius cubed.

Separation of a planetary body into layers of differing density, such as core, mantle and crust, driven by melting and gravity early in its history.

The fixed interval in which half of a radioactive parent isotope decays to its daughter, allowing measured isotope ratios to be converted into absolute ages for rocks and minerals.

An indirect archive of past conditions, such as ice cores, tree rings, sediment layers or coral chemistry, whose measurable properties are calibrated against instrumental data to infer ancient environments.

The quantified range within which a measured or inferred value is expected to lie, arising from instrument limits, sampling and natural variability, and essential when judging whether trends are real.

Reconstruction of past positions of continents and oceans from magnetic anomalies, fossil and rock correlations, and geometric fitting, testing hypotheses about ancient climates and biogeography.

The record of ancient magnetic field direction and intensity preserved in magnetic minerals in rocks, used to track plate motion, continental drift and reversals of Earth's field.