SACE Stage 2 Earth and Environmental Science key terms

The rigid outer shell of Earth, made of the crust and the uppermost solid mantle. It is broken into tectonic plates that move slowly over the softer layer beneath.

The hot, partly molten layer of the mantle just below the lithosphere. It flows very slowly, allowing the rigid plates above it to shift and drift over long periods.

The theory that Earth's lithosphere is divided into plates that move relative to each other, driven by mantle motion. Their collisions, separations and slides cause earthquakes, volcanoes and mountain building.

A circular pattern of movement in a fluid caused by heating from below and cooling from above. In the mantle, hot rock rises, spreads, cools and sinks, helping to drive plate motion.

The process where one tectonic plate, usually denser oceanic crust, sinks beneath another plate into the mantle. It produces deep ocean trenches, earthquakes and chains of volcanoes.

A long underwater mountain range formed where two plates pull apart and magma rises to create new oceanic crust. New sea floor spreads outward from the ridge on both sides.

The gradual addition of new oceanic crust at mid-ocean ridges as magma rises and solidifies, pushing older crust sideways. Magnetic stripes in the crust record reversals of Earth's field and support the process.

The set of natural processes that transform rock among igneous, sedimentary and metamorphic forms through melting, cooling, weathering, erosion, deposition and heat and pressure.

The breakdown of rock and minerals where they lie, by physical, chemical or biological processes. The broken material stays in place unless it is later moved by erosion.

The removal and transport of weathered rock, soil and sediment by agents such as water, wind, ice or gravity. It shapes landforms and moves material to new locations for deposition.

The laying down of transported sediment, soil or dissolved material when the carrying agent loses energy. Deposited layers may later be compacted and cemented into sedimentary rock.

Rock formed from deposited sediment or from minerals left by evaporation, then compacted and cemented over time. Its layers often preserve fossils and evidence of past environments.

Preserved remains, impressions or traces of once-living organisms, usually found in sedimentary rock. Fossils provide evidence of past life, environments and the relative ages of rock layers.

The study of the order and arrangement of layered rock, especially sedimentary strata. Its principles allow geologists to establish relative ages and correlate layers across different locations.

Working out the sequence in which events or rock layers occurred, without giving exact ages. It uses principles such as superposition, cross-cutting relationships and fossil succession.

A method of finding the absolute age of a material by measuring the ratio of a radioactive parent isotope to its decay product, using the known half-life.

The time taken for half of the atoms of a radioactive isotope in a sample to decay. Each isotope has a fixed half-life, which allows radiometric dating over different time ranges.

The warming of a planet's surface because certain gases in the atmosphere absorb outgoing infrared radiation and re-emit some of it back toward the surface, slowing heat loss to space.

A gas whose molecules absorb and re-emit infrared radiation, such as carbon dioxide, methane, water vapour and nitrous oxide. Higher concentrations strengthen the greenhouse effect and warm the surface.

A reservoir or process that removes more carbon from the atmosphere than it releases, such as forests, soils or oceans. Sinks slow the rise in atmospheric carbon dioxide.

A reservoir or process that releases more carbon to the atmosphere than it absorbs, such as burning fossil fuels, deforestation or volcanic activity. Sources increase atmospheric carbon dioxide.

The change in the balance of incoming and outgoing energy at the top of the atmosphere caused by a factor such as a gas increase or a change in solar output, measured in watts per square metre.

A process in which a change causes further changes that either amplify the original change (positive feedback) or reduce it (negative feedback). Feedback shapes how strongly a climate system responds.

The fraction of incoming solar radiation that a surface reflects. Bright surfaces such as ice and snow have high albedo, while dark surfaces such as open ocean absorb more energy.

Indirect evidence used to reconstruct past climates, such as tree rings, ice cores, corals, sediments and pollen. Proxy data let scientists extend climate records far beyond direct measurements.

A cylinder of ice drilled from a glacier or ice sheet that preserves layers of snow from past years. Trapped air bubbles and isotope ratios reveal past temperatures and greenhouse gas levels.

A carbon-rich fuel such as coal, oil or natural gas formed from buried organic matter over millions of years. Burning it releases carbon dioxide and other gases into the atmosphere.

A natural resource that is replenished by natural processes at a rate comparable to or faster than its use, such as solar energy, wind, flowing water or timber from managed forests.

A natural resource that forms very slowly or is fixed in amount, so it is used up faster than it is replaced. Fossil fuels and most mineral ores are examples.

Meeting present needs without reducing the ability of future generations to meet their own needs. It involves balancing environmental, social and economic factors in resource use.

The maximum population of a species that an environment can support indefinitely given its resources. Exceeding it leads to resource depletion, decline or environmental damage.

A benefit that people obtain from functioning ecosystems, such as clean water, pollination, flood control or food. These services can be degraded by overuse or pollution.

The upper surface of the zone where all spaces in soil and rock are filled with water. Its level rises and falls with recharge and extraction and affects wells and springs.

A layer of rock or sediment that can store and transmit useful amounts of groundwater. Water can be extracted from it through wells, sometimes faster than it is recharged.

Water held beneath the ground surface in pores and cracks of soil and rock. It supplies wells and springs and can be depleted or contaminated by human activity.

A testable, falsifiable statement that proposes an explanation for an observation. It guides an investigation and is supported or rejected by evidence collected in experiments.

The factor that an investigator deliberately changes or selects in an experiment. Its effect is observed by measuring the dependent variable while other factors are controlled.

The factor that is measured or observed in an experiment and is expected to respond to changes in the independent variable.

A factor that is kept constant across trials so that it cannot affect the outcome. Controlling variables increases confidence that observed changes are due to the independent variable.

The extent to which repeated measurements or trials give consistent results. It is improved by taking multiple readings, using larger samples and controlling sources of variation.

The extent to which an investigation actually measures what it claims to measure and its conclusion follows from the evidence. Poorly controlled variables or biased methods reduce validity.

How closely repeated measurements of the same quantity agree with each other, often reflected in the number of significant figures and the size of random error.

How close a measured value is to the true or accepted value. Systematic errors, such as an uncalibrated instrument, reduce accuracy even when readings are precise.

A statistical relationship in which two variables change together. Correlation alone does not prove that one variable causes the other, because other factors may be involved.