BGCSE Geography (Botswana Senior Secondary Education BSSE) flashcards

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

Lithosphere

The rigid outer shell of Earth made of the crust and uppermost mantle, broken into tectonic plates that move over the weaker asthenosphere.

Isostasy

The state of balance in which lighter or thicker crust floats higher on the denser mantle, so loading causes subsidence and unloading causes uplift.

Subduction zone

A convergent boundary where a denser oceanic plate sinks beneath a lighter plate, producing deep ocean trenches, earthquakes and volcanic arcs.

Sea-floor spreading

The process at mid-ocean ridges where magma rises, cools to form new oceanic crust, and pushes older crust sideways away from the ridge.

Epicentre

The point on Earth's surface directly above the focus of an earthquake, where shaking is usually strongest.

Coriolis effect

The apparent deflection of moving air or water caused by Earth's rotation, to the right in the Northern Hemisphere and to the left in the Southern.

Relative humidity

The amount of water vapour in the air expressed as a percentage of the maximum the air could hold at that temperature.

Relief rainfall

Rain produced when moist air is forced to rise over hills or mountains, cools, condenses, and falls on the windward slopes.

Water table

The upper surface of saturated rock or soil where all pore spaces are filled with water, below which groundwater is stored.

Infiltration

The downward movement of water from the surface into soil and rock pores, which is faster on permeable, vegetated and gentle surfaces.

Watershed

The boundary, usually a ridge of high land, separating one drainage basin from another and dividing the direction of runoff.

Hydraulic action

River or wave erosion caused by the force of moving water compressing air in cracks, weakening and eventually breaking up rock.

Oxbow lake

A crescent-shaped lake formed when a meander loop is cut off from the main river channel by erosion and deposition.

Discharge

The volume of water flowing past a point in a river per second, calculated as cross-sectional area multiplied by mean velocity.

Longshore drift

The zigzag movement of sediment along a coast as waves approach at an angle, carrying material in the direction of the dominant waves.

Spit

A ridge of deposited sand and shingle extending from the land into the sea, formed where longshore drift continues across a river mouth or bay.

Fringing reef

A coral reef growing directly along a coastline in warm, shallow, clear water, forming a natural barrier against wave energy.

Trophic level

A feeding position in a food chain, such as producer or primary consumer, through which energy passes with about 90% lost at each transfer.

Mangrove

A salt-tolerant tree community growing in tropical coastal mudflats, providing nursery habitat for fish and reducing coastal erosion.

Leaching

The removal of soluble nutrients from upper soil horizons by downward-moving water, common in wet climates and causing low fertility.

Soil texture

The relative proportions of sand, silt and clay particles in a soil, which control drainage, water retention and workability.

Natural increase

The difference between the birth rate and the death rate of a population, usually expressed per thousand people per year.

Population density

The average number of people living in each square kilometre of an area, calculated by dividing population by total area.

Demographic transition

A model showing how birth and death rates change as a country develops, moving from high stationary to low stationary populations.

Multiplier effect

The process by which new investment creates jobs and income, generating further local demand and additional employment.

Value added

The difference between the selling price of a product and the cost of the inputs used to make it, indicating income generated.

Subsistence farming

Farming that produces mainly food for the farmer's own family, with little or no surplus sold at market.

Ecotourism

Tourism focused on natural environments that aims to conserve them and benefit local communities while limiting visitor impact.

Urban sprawl

The uncontrolled outward spread of a city into surrounding countryside, increasing car dependence and service costs.

Rural-urban fringe

The zone where a town meets the countryside, containing mixed land uses such as housing estates, farmland, airports and golf courses.

Storm surge

A rise in sea level near a coast caused by low pressure and strong onshore winds during a hurricane, causing severe flooding.

Contour lines

Lines on a map joining points of equal height above sea level; close spacing shows steep slopes and wide spacing shows gentle slopes.