GCE A/L Geography key terms

The process where a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent boundary, generating deep ocean trenches, earthquakes and magma that feeds volcanic arcs.

A plate margin where two lithospheric plates move towards each other, producing subduction, collision or mountain building depending on the plate types involved.

The creation of new oceanic crust at mid-ocean ridges as magma rises and solidifies, pushing older crust sideways and recording magnetic reversals in symmetrical stripes.

A dipping plane of earthquake foci that marks the descending slab of a subducting plate, reaching depths of up to about 700 km beneath island arcs.

A fixed plume of anomalously hot mantle that melts the overriding plate to produce volcanism, often forming chains of islands as the plate moves over it.

A relative rise or fall of land level caused by changes in the load or buoyancy of the crust, for example unloading by ice-sheet melt or loading by sediment.

A global change in sea level caused by alterations to the volume of water in the oceans or the capacity of ocean basins, notably thermal expansion and ice-sheet melt.

The zigzag movement of sediment along a coastline as waves approach at an oblique angle, carrying material in the swash and returning it at right angles in the backwash.

A largely self-contained stretch of coastline within which sediment is recycled between sources, transfer zones and sinks, used as a unit for coastal management.

The loss of intertidal habitat when rising sea levels push ecosystems landwards against fixed defences or developed land, leaving no room for landward migration.

Erosion caused by rock fragments embedded in the base of a glacier scraping and smoothing the bedrock as the ice slides over it, producing striations and rock polish.

The process by which meltwater freezes into joints in bedrock, and the glacier then tears away blocks of rock as it moves, leaving jagged, quarried surfaces.

Describing environments marginal to ice sheets where freeze-thaw processes dominate, typically underlain by permafrost and shaped by ground ice, solifluction and patterned ground.

Ground that remains at or below 0°C for at least two consecutive years, often with an active layer that thaws each summer and can become unstable when degraded.

The slow downslope flow of water-saturated soil above a frozen layer, producing lobate sheets typical of periglacial slopes during seasonal thaw.

A graph plotting river discharge against time after a rainfall event, showing lag time, peak discharge and the rising and falling limbs of the flow.

The delay between the peak of rainfall and the peak of river discharge, shortened by impermeable surfaces, steep slopes, compacted soil and drainage channels.

The condition in which a population lacks reliable access to sufficient, safe and affordable water for health, livelihoods and ecosystems, often driven by scarcity, pollution or poor governance.

The volume of water embedded in the production of a good or service, transferred between regions through trade and often used to relieve local water scarcity.

The proportion of incoming solar radiation reflected by a surface; ice and snow have high values while oceans and forests have low ones, creating feedbacks in the climate system.

The additional warming caused by human emissions of greenhouse gases such as carbon dioxide and methane, adding to the natural greenhouse effect that keeps Earth habitable.

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

The tendency for built-up areas to be warmer than surrounding rural areas because of heat storage in concrete, reduced vegetation, vehicle emissions and low evaporation.

A model describing the sequence of changes in birth and death rates as a country develops, moving from high stationary through transitional stages to low stationary and declining populations.

A paired bar chart showing the age and sex structure of a population, whose shape reveals past fertility, mortality and migration and indicates likely future needs.

The proportion of a population outside working age compared with those of working age, indicating the economic burden of supporting children and elderly people.

Conditions that respectively drive people away from a source area, such as conflict or unemployment, and attract them to a destination, such as jobs or safety.

The in-migration of wealthier residents into a previously deprived inner-city area, raising property prices and rents and often displacing lower-income occupants.

The movement of people and economic activity from cities to smaller towns and rural areas, driven by housing costs, quality of life and improved transport links.

The outward, low-density expansion of built-up areas into surrounding countryside, increasing car dependence, infrastructure costs and loss of agricultural or green land.

The principle that a country benefits from specialising in goods it can produce at a lower opportunity cost than trading partners, even if it is less efficient in absolute terms.

The ratio of a country's export prices to its import prices, indicating how much imported goods can be bought with a given volume of exports.

The growing interconnection of economies, cultures and societies through trade, investment, migration and communication, enabled by falling transport costs and digital technology.

A firm that operates production or service facilities in more than one country, often locating stages of its supply chain to exploit cost, market or regulatory differences.

The combination of primary energy sources a country uses, such as coal, gas, nuclear, hydro and wind, determined by resource endowment, cost, policy and technology.

Reliable, affordable and uninterrupted access to energy supplies, threatened by dependence on imports, political instability, price volatility and inadequate infrastructure.

The state in which all people have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and preferences.

The distance food travels from production to consumption, used as an indicator of the environmental cost of food supply chains alongside other measures.

A statistical test measuring the strength and direction of a monotonic relationship between two ranked variables, giving a value from -1 to +1 that can be tested for significance.

A non-parametric test comparing whether two independent samples differ significantly, used when data are ordinal or not normally distributed.

The selection of representative sites or individuals for measurement, using strategies such as random, systematic or stratified sampling to reduce bias in fieldwork data.