AP Intermediate Geography (BIEAP) key terms

The boundary surface separating Earth's crust from the mantle, marked by an abrupt increase in seismic wave velocity. It lies about 5–10 km below ocean floors and 30–70 km beneath continents.

The rigid outer shell of Earth comprising the crust and uppermost mantle, roughly 100 km thick. It is broken into tectonic plates that move over the weaker asthenosphere beneath.

Vibrations generated by earthquakes or explosions that travel through Earth. P-waves compress rock and pass through solids and liquids, while S-waves shear rock and cannot travel through liquids.

The theory explaining that Earth's lithosphere is divided into plates which drift on the asthenosphere. Their convergence, divergence and lateral sliding produce earthquakes, volcanoes, fold mountains and ocean trenches.

The process in which a denser oceanic plate sinks beneath a lighter continental or oceanic plate at a convergent boundary. It generates deep-sea trenches, volcanic arcs and powerful earthquakes.

The focus is the point inside Earth where an earthquake originates; the epicentre is the point on the surface directly above it. Shaking is usually strongest near the epicentre.

The breakdown of rocks in situ by physical, chemical or biological processes without transport of the debris. It produces regolith and prepares material for erosion and soil formation.

The removal and transport of weathered rock material by running water, wind, ice or waves. It shapes landforms such as valleys, gorges and deltas over long periods.

The laying down of eroded sediment when the transporting agent loses energy, for example where a river enters a sea or a glacier melts. It builds landforms such as deltas, floodplains and moraines.

Loose, fertile sediment of sand, silt and clay deposited by rivers. Extensive alluvial plains and deltas, such as those of the Godavari and Krishna, support intensive agriculture.

A vertical section through soil showing its horizons from surface to parent rock. Typical horizons are O (organic litter), A (topsoil), B (subsoil), C (weathered rock) and R (bedrock).

A dark clay-rich soil formed from basaltic lava, rich in iron and magnesia and highly moisture-retentive. It develops deep cracks when dry and is important for cotton in the Deccan region.

Incoming solar radiation received at Earth's surface, measured per unit area over time. Its intensity varies with latitude, season and angle of the sun's rays, driving atmospheric circulation.

Zonal bands of high and low atmospheric pressure produced by unequal heating and air movement: equatorial low, subtropical high, subpolar low and polar high. They shift seasonally with the sun.

A seasonal reversal of prevailing winds caused by differential heating of land and sea, bringing a wet summer and dry winter to South Asia. The Indian monsoon governs agriculture across the subcontinent.

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 is zero at the equator and strongest at the poles.

Large-scale, persistent movements of ocean water driven by winds, differences in temperature and salinity, and Earth's rotation. Warm and cold currents moderate coastal climates and influence fishing grounds.

The concentration of dissolved salts in seawater, usually expressed in parts per thousand. It averages about 35 ppt and varies with evaporation, precipitation, river inflow and ice melt.

The number of live births per 1,000 people in a population in a given year. Together with the death rate it determines the natural rate of population growth.

The number of deaths per 1,000 people in a population in a given year. Falling death rates, rather than rising birth rates, usually drive the early stages of demographic transition.

A model describing the shift of a population from high birth and death rates to low ones as a society develops. It passes through stages of early expanding, late expanding and low stationary growth.

The average number of people living per unit area, commonly per square kilometre. It reveals uneven distribution but conceals internal variation within a region.

The increasing share of a population living in towns and cities, accompanied by the growth of urban areas. It results from rural-to-urban migration and natural increase in cities.

A continuous urban area formed when expanding towns and cities merge into one another. Examples include the Mumbai–Pune corridor and the Kolkata metropolitan region.

Farming that produces mainly for the farmer's own family, using small plots and simple tools. It is labour-intensive, low-yielding and common in densely populated tropical regions.

Large-scale farming aimed at selling produce in markets, using machinery, fertilisers and hired labour. It is capital-intensive and typical of sparsely populated plains such as North America's prairies.

Farming that obtains high output per unit of land through heavy inputs of labour, water, fertiliser or technology. It includes wet rice cultivation in Asia and market gardening near cities.

An industry whose location is not tied to raw materials because its products are light and easily transported, such as electronics or software. It favours places with skilled labour and good infrastructure.

The conditions that influence where a factory is sited: raw materials, power, water, transport, labour, capital, markets and government policy. Their relative importance varies with the type of industry.

A large triangular plateau of peninsular India bounded by the Western and Eastern Ghats, formed largely of ancient crystalline rocks and basalt lava flows. It is drained by the Godavari, Krishna and Kaveri.

The southeastern coast of India along the Bay of Bengal, from Point Calimere to the Krishna delta. It receives most rain from the retreating northeast monsoon and is noted for rice and deltaic agriculture.

The second longest river of India, rising in the Western Ghats near Nashik and flowing east across the Deccan into the Bay of Bengal. Its large delta is a major rice-growing region.

The ratio between distance on a map and the corresponding distance on the ground, shown as a representative fraction, verbal statement or linear bar. It allows real distances to be measured from the map.

A line on a topographic map joining points of equal elevation above sea level. Spacing shows slope steepness, while the shapes reveal ridges, valleys and other relief features.

A set of numbers locating a point on a map by its easting and northing coordinates. In a four-figure reference the square is identified; a six-figure reference pinpoints a position within it.

A line along which observations are recorded during field study to reveal changes across an area, such as from a river bank to a hilltop. Data are plotted as a cross-section or graph.