NSSCAS Geography 8233 key terms

The drop in temperature of an air parcel as it rises and expands under lower pressure, without gaining or losing heat to its surroundings. It drives cloud formation and orographic rainfall.

The actual rate at which still air temperature falls with height in the troposphere, averaging about 6.5 degrees Celsius per kilometre but varying with local conditions and humidity.

A layer of the atmosphere where temperature increases with height instead of falling. It traps pollutants and moisture beneath it, producing fog and smog in valleys and cities.

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. It shapes global wind belts and ocean currents.

The rate of change of atmospheric pressure over horizontal distance. A steep gradient produces strong winds, while a gentle gradient gives light winds and calm conditions.

A high-pressure system where air descends and diverges at the surface. It usually brings settled, clear weather in summer but can produce fog, frost and temperature inversions in winter.

Rain produced when moist air is forced to rise over hills or mountains, cooling and condensing on the windward slope while leaving a drier rain shadow on the leeward side.

The tendency of built-up areas to be warmer than surrounding countryside, caused by heat-absorbing surfaces, reduced vegetation, traffic and domestic heating, and trapped pollution.

The whole area of land drained by a river and its tributaries, bounded by a watershed. Its inputs, stores and outputs of water form a useful system for study.

A graph plotting river discharge against time after a rainfall event. It shows the lag time, peak discharge and recession limb, revealing how a basin responds to precipitation.

The delay between the peak of rainfall and the peak of river discharge in a drainage basin. Short lag times indicate rapid runoff, often linked to impermeable surfaces or steep slopes.

The movement of sediment along a coast in a zigzag path, as waves arrive at an angle and backwash returns perpendicular to the shore. It builds spits and bars.

A narrow ridge of sand or shingle extending from the land into open water, formed by longshore drift continuing across a bay or river mouth where the coastline changes direction.

The zone where two lithospheric plates meet, either diverging, converging or sliding past each other. Each type produces characteristic earthquakes, volcanoes and landforms.

The process where a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent boundary, generating deep ocean trenches, earthquakes and volcanic arcs.

The breakdown of rock in situ by physical, chemical or biological processes, without the transport of material. It prepares rock for erosion and shapes slopes and soils.

The downslope transfer of rock, soil or mud under gravity, ranging from slow creep to rapid landslides and mudflows. Water content and slope angle strongly influence its speed.

A community of living organisms interacting with each other and their non-living environment, exchanging energy and nutrients. Examples include tropical rainforest, savanna and coral reef.

The circulation of elements such as carbon, nitrogen and phosphorus between living organisms, soil, water and atmosphere. Rapid recycling supports dense rainforest, while leaching depletes poorer soils.

The removal of soluble nutrients and minerals from soil by downward-percolating rainwater. It is intense in hot, wet climates and leaves soils acidic and infertile.

A vertical section through soil showing distinct horizons from surface litter to parent material. The arrangement of horizons reflects climate, vegetation, drainage and time.

The variety of living things within a place, measured at genetic, species and ecosystem levels. High biodiversity is typical of tropical rainforests and coral reefs and is threatened by habitat loss.

A paired bar graph showing the age and sex structure of a population. Its shape reveals birth rates, death rates, migration and dependency ratios, and helps predict future needs.

A model describing how birth and death rates change as a country develops through stages from high stationary to low stationary. It helps explain population growth patterns over time.

The proportion of people too young or too old to work compared with the working-age population. A high ratio places pressure on services, carers and government spending.

A population with a rising share of older people, caused by falling birth rates and longer life expectancy. It raises demand for healthcare and pensions and can shrink the labour force.

Conditions that drive people away from a place, such as poverty or conflict, and attractions that draw them elsewhere, such as jobs or safety. Together they explain migration decisions.

The permanent or semi-permanent movement of people between places, whether within a country or across borders. It may be voluntary or forced and changes both source and destination areas.

Money sent by migrants back to their home country or region. They can support families, fund education and housing, and form a significant share of national income in some economies.

The difference in wealth, income and quality of life between richer and poorer countries or regions. It is measured by indicators such as GDP per capita and the Human Development Index.

A composite measure combining life expectancy, education and income per person to rank countries by human wellbeing. It gives a broader picture than income alone.

The total value of goods and services produced within a country in a year. It is a common measure of economic output but ignores inequality and unpaid work.

Economic activity that is unregistered and unregulated, such as street trading or casual labour. It provides income for many urban poor but offers little security or protection.

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 and service provision.

The movement of people from cities to smaller settlements or rural areas, often after retirement or as commuting becomes possible. It can revitalise villages but raises house prices.

The transformation of countryside areas through agricultural modernisation, diversification, tourism or in-migration. It alters employment, landscapes and community structures.

Disagreement between groups with competing interests in how a piece of land should be used, such as housing, farming, recreation or conservation. Planners seek to balance these demands.

Meeting present needs without compromising the ability of future generations to meet theirs. It balances economic growth, social wellbeing and environmental protection in policy and planning.

The planned use and conservation of natural resources such as water, energy and minerals to balance supply, demand and environmental impact over time.

A situation where demand for water approaches or exceeds reliable supply, causing shortages, competition between users and environmental damage. It is worsened by population growth and climate change.

Selecting a representative subset of a population or environment for measurement, using strategies such as random, systematic or stratified methods to reduce bias in fieldwork data.

The extent to which repeated measurements or observations give consistent results. It is improved by careful technique, adequate sample size and clear recording methods.

The degree to which data or a method actually measures what it claims to measure. A valid study answers the research question rather than collecting irrelevant information.

A map in which areas are shaded or patterned in proportion to a value, such as population density. It shows broad patterns clearly but can hide variation within large areas.