Cameroon GCE A-Level Geography key terms

The theory that Earth's outer shell is broken into large rigid slabs that drift over the mantle, colliding, separating or sliding past each other and so generating earthquakes, volcanoes and mountain belts.

A belt where one tectonic plate sinks beneath another, producing deep ocean trenches, earthquakes and chains of volcanoes such as the Cameroon Volcanic Line's offshore segment.

The inclined band of earthquake foci that marks a descending oceanic slab, deepening inland from a trench and used as evidence for plate subduction.

A long trough formed where the crust is pulled apart and a block sinks between parallel faults, as along the Cameroon Volcanic Line and the wider Gulf of Guinea rift system.

A fracture in the crust along which rocks have moved, often marked by springs, scarps and aligned valleys, and a common site of earthquake activity.

A linear chain of volcanoes and intrusive centres not parallel to a plate margin, such as the Cameroon Volcanic Line running from the Gulf of Guinea through Mount Cameroon to the Adamawa Plateau.

A fixed zone of upwelling heat in the mantle that melts the crust above it, creating volcanic centres; movement of the plate over it can produce chains of volcanoes.

The breakdown of rock in place by physical, chemical or biological processes, producing regolith; it is distinct from erosion, which removes the material.

A hard, iron- and aluminium-rich crust that forms in humid tropical areas where heavy leaching removes silica and bases, leaving behind resistant sesquioxides.

The downward washing of soluble bases and nutrients out of soil by percolating rainwater, common under high rainfall and responsible for the low fertility of many tropical soils.

A vertical section through soil showing its horizons from surface litter down to weathered bedrock, used to compare fertility and development between sites.

The downslope transfer of soil and rock under gravity, ranging from slow creep to rapid landslides and mudflows, often triggered by heavy rain or slope undercutting.

Sudden collapse of a hillside when shear stress exceeds the strength of the material, frequently caused by saturation, deforestation or road cutting on steep terrain.

The whole area drained by a river and its tributaries, bounded by a watershed; it acts as a system with inputs of precipitation and outputs of discharge and evaporation.

The boundary, usually a ridge or crest, separating one drainage basin from another; rain falling on either side flows into different river systems.

A graph plotting river discharge against time after a rainfall event, showing lag time, peak flow and recession, and revealing how a basin stores and releases water.

A river channel divided into several shifting threads by bars of coarse sediment, typical where load is abundant and discharge fluctuates, as in some Sahelian and mountain streams.

The flat land bordering a river, built up by alluvium during overbank floods and often used for farming because of its fertile, easily worked soils.

Fine sediment of silt, sand and clay deposited by flowing water on flood plains, in deltas and in channel beds, generally making fertile and workable farmland.

A low-lying tract of sediment built where a river enters standing water and loses velocity, often forming distributary channels and valuable agricultural land.

The upper surface of saturated rock or soil, which rises in the wet season and falls in the dry season and controls where wells and springs yield water.

A permeable rock or sediment layer that stores and transmits groundwater in usable quantities, recharged by rainfall and tapped by wells and boreholes.

The average and range of weather conditions at a place over many years, described by temperature, rainfall, humidity and wind, and controlled by latitude, altitude and distance from the sea.

The belt near the equator where the trade winds of both hemispheres meet, producing rising air, heavy convectional rain and a marked wet season.

Rain produced when moist air is forced to rise over high ground, cooling and condensing on the windward side while leaving a drier rain-shadow on the leeward side.

The spread of desert-like conditions into formerly productive dry land through drought, overgrazing, deforestation and poor farming, reducing vegetation cover and soil quality.

The permanent removal of forest cover for timber, fuel, farming or settlement, leading to soil erosion, loss of biodiversity and changes in local runoff and climate.

Keeping more livestock on a pasture than it can support, so that vegetation is stripped, soil is exposed and erosion or desertification follows.

The average number of people per unit area, usually per square kilometre, calculated by dividing total population by total land area of the territory.

The pattern of where people live across a territory, ranging from sparse upland or forest zones to crowded towns, plantations and coastal settlements.

A paired bar chart showing the number or percentage of males and females in each age group, revealing birth rates, dependency ratios and past shocks such as epidemics or conflict.

The number of children and elderly people compared with the working-age population, showing how many dependants each worker must support.

The movement of people from one place to another to live, either within a country or across a border, driven by push factors such as poverty and pull factors such as jobs.

Movement of people from villages to towns and cities in search of work, education and services, which swells urban populations and can leave farmland underused.

The rising proportion of a population living in towns and cities, accompanied by the physical growth of built-up areas and demand for housing, water and transport.

A city that is disproportionately larger and more influential than the second city of the same country, concentrating administration, trade and services.

A crop grown mainly for sale rather than subsistence, such as cocoa, coffee or cotton, which earns export income but exposes farmers to world price changes.

Farming that produces mainly food for the farmer's own household, using simple tools and small plots, with little surplus for sale.

A farming system in which plots are cleared, cropped for a few years and then abandoned to recover fertility while the farmer moves on.

A large estate growing one crop, usually for export, with hired labour and capital investment in processing and transport, typical of cocoa and oil-palm estates.