MATSEC AM Geography key terms

The continuous movement of water between oceans, atmosphere, land and living things through evaporation, condensation, precipitation, interception, infiltration, runoff and storage, driven mainly by solar energy and gravity.

The downward movement of water from the ground surface into soil pores and rock openings. The rate depends on soil texture, slope, vegetation cover, antecedent moisture and whether the surface is sealed by concrete or compaction.

The slow downward movement of water through saturated or partly saturated rock and soil towards the water table. It recharges aquifers and is slower than infiltration because pore spaces in bedrock are smaller.

Water that flows over the land surface rather than soaking in, feeding streams and rivers. It increases when rainfall intensity exceeds infiltration capacity, when slopes are steep, or when vegetation and soil are removed.

The upper surface of the zone of saturation in permeable rock or soil, below which all pore spaces are filled with water. It rises and falls with rainfall, pumping and seasonal demand.

A body of permeable rock or sediment, such as sandstone, chalk or gravel, that can store and transmit usable quantities of groundwater. An aquifer is recharged by percolation and tapped by wells and boreholes.

The whole area of land drained by a river and its tributaries, bounded by higher ground along the watershed divide. Its size, geology, land use and climate determine the river's discharge regime.

A graph plotting river discharge against time after a rainfall event, showing the rising limb, peak discharge and recession limb. Steep, short hydrographs indicate rapid runoff from impermeable or urbanised catchments.

The volume of water passing a given point in a river per unit time, usually measured in cubic metres per second. It equals cross-sectional area multiplied by mean velocity and varies with rainfall and season.

The flat land beside a river that is built up by alluvium and covered by water during floods. It absorbs flood peaks, stores water and provides fertile farmland, but is often built on by expanding settlements.

Fine sediment of silt, sand and clay deposited by a river on its flood plain, in deltas or on the inside of meanders. Alluvium is fertile and easy to work, so it often supports intensive agriculture.

A broad bend in a river channel formed by lateral erosion on the outer bank and deposition on the inner bank. Continued migration and cut-off of meanders produce oxbow lakes and wide flood plains.

A cross-section of a river from source to mouth showing how gradient and height above sea level change downstream. It is typically concave, steep in the upper course and almost flat near the mouth.

The in-situ breakdown or decay of rock at or near the Earth's surface by physical, chemical or biological processes. Weathering produces regolith but does not itself transport the broken material.

The downslope transfer of soil and rock under gravity, ranging from slow creep to rapid landslides and mudflows. Slope angle, water content, vegetation and human activity such as undercutting influence its speed and type.

The zone where two lithospheric plates meet, either diverging at a constructive boundary, converging at a destructive boundary or sliding past at a conservative one. Most earthquakes and volcanoes occur along such boundaries.

The process where a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent boundary. It generates deep ocean trenches, earthquakes, fold mountains and chains of volcanic arcs.

The creation of new oceanic crust at mid-ocean ridges as magma rises and solidifies, then moves away on either side. The ocean floor therefore widens and records magnetic reversals in symmetrical stripes.

A fracture in the Earth's crust along which movement has occurred. Sudden slip on faults releases stored strain as earthquakes, while repeated movement can form rift valleys and offset rock layers.

The point within the Earth where an earthquake originates and where seismic energy is released. Its depth controls how widely and how severely the shock is felt at the surface.

The point on the Earth's surface directly above an earthquake's focus. Shaking and damage are usually greatest near the epicentre, weakening outwards as seismic waves spread and lose energy.

An instrument that records ground motion during an earthquake as a trace called a seismogram. The difference in arrival times of P and S waves allows the distance to the focus to be estimated.

A landform where magma, ash and gases reach the surface through a vent. Eruption style depends on magma viscosity and gas content, producing either gentle lava flows or explosive pyroclastic activity.

A fast-moving, dense cloud of hot ash, pumice and gas that sweeps down a volcano's slopes. It is one of the most dangerous volcanic hazards because of its speed, heat and ability to destroy everything in its path.

A rapid flow of volcanic debris mixed with water, often triggered when ash and loose material are mobilised by heavy rain or melting snow. Lahars can travel far beyond the volcano and bury settlements.

A natural or human-induced event or condition that threatens life, property and livelihoods. A hazard becomes a disaster only when it affects a vulnerable population unable to cope with its impact.

The degree to which people, places or assets are likely to be harmed by a hazard because of exposure, poverty, poor building standards, weak governance or lack of preparedness. Reducing vulnerability lowers disaster risk.

The likelihood of harm occurring, combining the probability of a hazard event with the vulnerability and exposure of people and assets. Risk can be reduced by mitigation, preparedness and land-use planning.

Actions taken to reduce the severity or likelihood of hazard impacts, such as flood defences, earthquake-resistant buildings, afforestation and land-use zoning. Mitigation differs from adaptation in that it targets the hazard or its effects directly.

Long-term shifts in temperature, precipitation and wind patterns, currently driven mainly by human emissions of greenhouse gases. Effects include sea-level rise, more intense rainfall and shifting agricultural zones.

The warming of the lower atmosphere as gases such as carbon dioxide, methane and water vapour absorb outgoing infrared radiation and re-emit it towards the surface. It makes Earth habitable but is being strengthened by human emissions.

Adjusting systems and practices to reduce harm from actual or expected climate impacts, for example drought-resistant crops, coastal defences or early-warning systems. Adaptation addresses consequences rather than the causes of climate change.

A graph showing the age and sex structure of a population as horizontal bars. Its shape reveals birth and death rates, migration history and the dependency burden on the working-age population.

A model describing how birth and death rates change through stages as a country develops, moving from high stationary rates to low stationary rates. It links population growth to economic and social change.

The proportion of people outside the working-age range (children and elderly) compared with those of working age. A high ratio places pressure on workers to support dependants through taxes and care.

The average number of people per unit area, usually per square kilometre. It is an average that hides uneven distribution, which is influenced by relief, climate, soils, resources and economic opportunity.

Conditions that drive people away from a place (push), such as unemployment or conflict, and conditions that attract them elsewhere (pull), such as jobs or services. Together they help explain migration flows and directions.

The permanent or semi-permanent movement of people from one place to another, either internally or across borders. It may be voluntary or forced and has economic, social and demographic effects on both source and destination.

A person who has fled their country because of war, persecution or disaster and cannot safely return. Refugees are protected under international law, unlike economic migrants who move mainly for work.

Money sent by migrants back to family in their home country. Remittances can be a major source of foreign income, supporting households, education and housing, though they may also create dependence.

The rising proportion of a population living in towns and cities, driven by rural-to-urban migration and natural increase. Rapid urbanisation can outpace housing, services and employment, creating informal settlements.

The outward spread of low-density development at the edge of cities, often consuming farmland and increasing car dependence. It results from rising incomes, cheap land and weak planning controls.

The purpose for which land is used, such as housing, industry, farming, recreation or conservation. Land-use patterns reflect physical conditions, accessibility, planning policy and competing economic demands.

The division of land into zones where particular uses are permitted, restricted or forbidden. Zoning aims to separate incompatible activities, protect amenities and manage growth, but can also segregate people and activities.

The cultivation of crops and rearing of livestock for food, fibre and fuel. Farming systems range from subsistence to commercial and intensive to extensive, shaped by climate, soils, technology and market access.

A system that obtains high output per unit area of land through heavy inputs of labour, capital, fertiliser, irrigation or machinery. It raises yields but can cause soil degradation, pollution and loss of biodiversity.

Reliable access by all people to sufficient, safe and nutritious food that meets their needs. It depends on availability, affordability, distribution and stability of supply, not simply on total production.

The growth of manufacturing and related activity as a share of an economy and workforce. It typically raises incomes and urban growth but brings pollution, resource demand and regional change.

A broad category of economic activity: primary (extraction), secondary (manufacturing), tertiary (services) and quaternary (knowledge and research). The balance between sectors changes as economies develop.

The growing interconnection of economies, cultures and societies through trade, investment, migration and communication. It spreads technology and lowers prices but can expose local industries and workers to intense competition.

A large company that operates production, sales or services in more than one country, often locating branches where costs or markets are favourable. Such firms can transfer jobs, technology and profits between countries.

The temporary movement of people to places away from home for leisure, business or other purposes, and the industries that serve them. It generates income and jobs but can strain resources and damage environments.

The maximum population or level of use an environment can support without lasting degradation. In tourism and recreation it marks the point beyond which visitor pressure damages resources and reduces visitor enjoyment.

Development that meets present needs without compromising the ability of future generations to meet theirs. It balances economic growth, social equity and environmental protection in decisions about land, resources and industry.

A population with a rising share of older people, caused by falling birth rates and longer life expectancy. It increases demand for health and care services and raises the dependency ratio.