GCE A/L Geography flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Subduction zone

A convergent boundary where denser oceanic lithosphere sinks beneath another plate, generating deep ocean trenches, earthquakes and volcanic arcs.

Moment magnitude scale

A logarithmic measure of earthquake energy release; each whole-number increase represents roughly 31.6 times more energy than the previous level.

Hotspot volcanism

Volcanic activity above a fixed mantle plume; as the plate moves, a chain of progressively older volcanoes forms, recording plate motion direction and rate.

Longshore drift

The movement of sediment along a coast by swash at an oblique angle and backwash at right angles, producing net transport in the dominant wave direction.

Discordant coastline

A coast where rock strata run perpendicular to the shoreline, producing alternating headlands and bays as resistant and less resistant rocks erode at different rates.

Sediment budget

The balance between sediment inputs to a coastal system and outputs from it; a negative budget causes net erosion and shoreline retreat.

Glacier mass balance

The difference between accumulation of snow and ice and ablation by melting, sublimation and calving; positive balance advances the glacier snout.

Drumlin

A streamlined mound of glacial till with a blunt stoss end and tapered lee end, indicating the direction of former ice flow.

Solifluction

Slow downslope flow of saturated soil over frozen ground or permafrost, common in periglacial environments during seasonal thaw of the active layer.

Storm hydrograph

A graph of river discharge against time after rainfall, showing rising limb, peak discharge, recession limb and lag time between rainfall and peak flow.

Water balance equation

Precipitation equals runoff plus evapotranspiration plus or minus change in storage, describing the inputs, outputs and stores of a drainage basin.

Virtual water

The volume of water used in producing a good or crop; importing water-intensive products effectively transfers water between countries.

Enhanced greenhouse effect

Additional warming caused by human emissions of greenhouse gases, which absorb and re-emit outgoing longwave radiation back towards the Earth's surface.

Milankovitch cycles

Long-term variations in Earth's orbit and axial tilt (eccentricity, obliquity and precession) that alter solar radiation receipt and drive glacial-interglacial cycles.

Urban heat island

The tendency of urban areas to be warmer than surrounding rural areas, caused by low-albedo surfaces, reduced evapotranspiration and anthropogenic heat release.

Dependency ratio

The number of people aged under 15 and over 64 divided by the working-age population aged 15 to 64, expressed per 100 workers.

Demographic transition model

A five-stage model describing changes in birth and death rates as a country develops, from high stationary through expanding stages to low stationary and declining.

Push and pull factors

Conditions at origin that drive people away (poverty, conflict, hazard) and conditions at destination that attract them (jobs, services, safety).

Bid-rent theory

A model explaining urban land use by the willingness of different activities to pay for central locations, with retail and offices outbidding others near the CBD.

Gentrification

The process by which wealthier residents and businesses move into a deprived urban area, raising property values and often displacing existing lower-income residents.

Counter-urbanisation

The movement of people from cities to rural areas, often driven by housing costs, quality of life and improved transport or remote working.

Comparative advantage

The principle that countries gain from specialising in goods they can produce at lower opportunity cost than trading partners, raising total output through trade.

Terms of trade

The ratio of a country's export prices to its import prices, expressed as an index; a fall means more exports are needed to buy the same imports.

Human Development Index

A composite development measure combining life expectancy, education (mean and expected years of schooling) and gross national income per capita.

Water-food-energy nexus

The interdependence between water, food and energy systems, where producing food and energy requires water and moving or treating water requires energy.

Energy mix

The combination of primary energy sources a country uses, such as coal, oil, gas, nuclear, hydro, wind and solar, affecting security and emissions.

Food security

A condition where all people have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs.

Spearman's rank correlation

A statistical test measuring the strength and direction of association between two ranked variables, giving a coefficient between minus one and plus one.

Systematic sampling

A sampling strategy selecting data points at regular intervals along a transect or grid, suitable for detecting gradients and easy to repeat.

Standard deviation

A measure of dispersion showing the average distance of data values from the mean; a large value indicates widely spread data.

Choropleth map

A map using shading or colour to represent the density or value of a variable across defined areas, such as population density by district.

Chi-squared test

A statistical test comparing observed frequencies with expected frequencies to determine whether differences between categories are statistically significant.