CIE A-Level Geography 9696 - Core Physical Geography Revision

Comprehensive vocabulary flashcards covering Topic 1 (Hydrology, river processes and hazards), Topic 2 (Atmospheric processes and global climate change), and Topic 3 (Earth processes and mass movements) for CIE A-Level Geography 9696.

Drainage basin

The land area drained by a river and its tributaries, separated from neighbouring basins by a watershed; operates as an open system where matter and energy cross its boundary.

Water balance

The hydrological relationship represented by the equation $P = Q + E + \text{change in storage}$, where $P$ is precipitation, $Q$ is runoff/discharge leaving the basin, and $E$ is evapotranspiration.

Interception store

Water temporarily retained on the leaves and branches of vegetation, which may either evaporate or reach the ground surface via throughfall and stemflow.

Groundwater store

Water stored in the fully saturated zone below the water table that sustains river baseflow during periods of dry weather.

Hortonian overland flow

Surface runoff that occurs when the rate of precipitation exceeds the infiltration capacity of the soil.

Saturation-excess overland flow

Surface runoff that occurs when rainfall lands on soil that has already reached full moisture saturation.

Porosity

The percentage of total void or open space within a body of soil or rock.

Permeability

The capacity of a rock or soil to transmit water through its interconnected pore spaces or fracture networks.

Lag time

The time delay between peak rainfall and peak river discharge on a storm hydrograph.

Baseflow

The sustained, slower contribution of groundwater flow feeding into a river channel, maintaining flow between rainfall events.

Hydraulic action

The mechanical erosive force of moving river water exerting pressure and compressing air within cracks along the bed and banks.

Abrasion (corrasion)

The mechanical wearing down and scouring of the channel bed and banks by transported sediment particles rubbing against them.

River competence

The maximum particle diameter or clast size that a river is capable of transporting under specific flow conditions.

River capacity

The total volume or quantity of sediment load that a river is able to transport at a given velocity and discharge.

Hjulstrom curve

A graphical model relating stream velocity to particle diameter, showing the critical threshold velocities required for erosion, transportation, and deposition.

Bradshaw model

A theoretical model illustrating downstream changes in a river, where channel width, depth, velocity, and discharge increase, while channel gradient and bedload particle size decrease.

Helicoidal flow

A corkscrew-like, cross-channel secondary water movement in meanders that drives erosion at the outer bank and transfers sediment to deposit on the inner bank.

Rejuvenation

Renewed vertical downcutting by a river caused by base-level fall, tectonic uplift, or increased discharge, forming features such as river terraces, knickpoints, and incised meanders.

Jubilee River

An approximately $11.6\,\text{km}$ artificial flood relief channel opened in 2002 designed to protect Maidenhead, Windsor, and Eton by diverting floodwater from the River Thames.

Environmental lapse rate

The average rate of temperature decrease with increasing altitude in the troposphere, measured at approximately $6.5^\circ\text{C per km}$.

Albedo

The fraction or percentage of incoming solar radiation reflected back into space by a surface.

Coriolis effect

The apparent force caused by Earth's rotation that deflects moving air and water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Dew point

The temperature to which an air parcel must be cooled at constant pressure and moisture content to reach $100\%$ relative humidity and achieve saturation.

Dry adiabatic lapse rate (DALR)

The rate at which an unsaturated parcel of dry air cools adiabatically as it rises through the atmosphere, equal to approximately $10^\circ\text{C per km}$.

Saturated adiabatic lapse rate (SALR)

The rate at which a saturated rising parcel of air cools adiabatically, variable but often around $4\text{--}7^\circ\text{C per km}$ due to the release of latent heat during condensation.

Convectional rainfall

Precipitation generated when strong ground heating warms the overlying air, causing it to become buoyant, rise, expand, cool adiabatically, and condense into towering cumulonimbus clouds.

Orographic (relief) rainfall

Precipitation produced when moist air is forced to ascend a mountain barrier, cooling adiabatically and raining on windward slopes while leaving a warm, dry rain shadow on leeward slopes.

Temperature inversion

An atmospheric situation where temperature increases with height, creating stable air conditions that suppress vertical motion and can trap pollution near the surface.

Lithosphere

The rigid, brittle outer layer of the Earth composed of the crust and uppermost solid mantle, broken into tectonic plates that move over the asthenosphere.

Asthenosphere

The semi-ductile, deformable upper mantle layer located beneath the rigid lithosphere, allowing tectonic plates to slide over it.

Palaeomagnetism

The record of past Earth magnetic reversals locked in cooling basaltic rock, showing symmetrical magnetic anomaly stripes across mid-ocean ridges that evidence seafloor spreading.

Slab pull

A major tectonic driving mechanism where the gravitational descent of cold, dense oceanic lithosphere sinking at subduction zones pulls the remainder of the plate along behind it.

Ridge push

A plate tectonic driving force resulting from the gravitational sliding of elevated, buoyant oceanic lithosphere down the slope away from mid-ocean ridges.

Lahar

A secondary volcanic hazard consisting of a fast-moving, destructive slurry or flow of water, mud, ash, and coarser volcanic debris.

Earthquake focus (hypocentre)

The precise subsurface rupture origin along a geological fault where accumulated elastic strain energy is abruptly released.

Epicentre

The geographic point located on the Earth's surface directly vertically above the underground focus (hypocentre) of an earthquake.

Mass movement

The downslope transfer of rock, soil, or superficial debris under the direct pull of gravity, occurring when shear stress exceeds shear strength.

Rotational slump

A mass movement slide where semi-coherent blocks of unconsolidated material or rock fail and rotate backward along a distinct curved, concave failure surface.

Soil creep

An extremely slow, continuous downslope movement of soil caused by repeated expansion and contraction cycles from freeze-thaw or wetting-drying, marked by terracettes and bent tree trunks.