Assam HS Higher Secondary Geography key terms

The overall wearing down of the land surface through the combined action of weathering, mass movement, erosion and transport, which gradually lowers the land towards base level.

The breakdown and decay of rock where it lies, caused by physical, chemical or biological processes, without the broken material being carried away; it prepares rock for erosion.

The removal and carrying away of weathered rock debris by a moving agent such as running water, wind, ice or waves, which at the same time cuts and reshapes the land.

A broad bend in a river's course produced by faster lateral erosion on the outer bank and slower deposition on the inner bank, most common in the middle and lower stages.

A crescent-shaped lake left behind when a river cuts across the narrow neck of a sharp meander and abandons the old loop; in Assam such lakes are commonly called beels.

The flat strip of alluvial land on either side of a river, built up by sediment laid down during repeated floods; it is usually fertile, easily irrigated and densely settled.

A river course split into several shallow, shifting sub-channels separated by temporary sandbars and islands, typical of streams carrying a heavy bed load such as the Brahmaputra.

The incoming solar radiation received at the top of the atmosphere or at the Earth's surface; its amount varies with latitude, season, angle of the sun and clearness of the air.

The share of incoming solar radiation that a surface reflects back, expressed as a percentage; fresh snow reflects most, while dark forest, bare soil and open water reflect much less.

A seasonal reversal of prevailing wind direction that brings a distinct rainy season and dry season; the South Asian monsoon arises mainly from unequal heating of land and sea.

A narrow, fast-flowing band of strong westerly wind near the tropopause; its northward shift helps the summer monsoon set in over India and its retreat aids withdrawal.

The water vapour actually present in the air, expressed as a percentage of the maximum the air could hold at that temperature; it falls when air is warmed without adding vapour.

A line drawn on a weather map through places reporting the same atmospheric pressure at the same moment; the pattern of isobars shows pressure systems and the strength of winds.

A violent pre-monsoon thunderstorm of eastern India and Assam, arriving mainly in April and May with towering dark cloud, strong squalls and heavy showers; locally called Bordoisila.

The upper surface of the saturated zone, below which every pore and crack in soil or rock is filled with water; it rises in the wet season and falls in the dry season.

A body of rock or sediment that can store and pass on groundwater in usable quantities; porous sandstone and gravel work well, while limestone transmits water mainly through joints.

The entire area drained by a river and its tributaries, enclosed by a divide; its size, shape, slope, soil and land use together control the flow reaching its outlet.

A vertical section through soil down to the underlying rock, showing separate horizons such as the organic surface layer, the topsoil, the subsoil and the weathered parent material.

The downward washing out of soluble salts and fine particles by percolating rainwater, common in wet climates and largely responsible for the low fertility of laterite soils.

Loose clay, silt, sand and gravel laid down by running water; the alluvial soils of the Brahmaputra and Barak valleys are the most extensive and productive soils of Assam.

The average number of people per unit of area, usually per square kilometre, found by dividing total population by total land area; it conceals uneven distribution within a region.

The number of females counted for every 1,000 males in a population, used as an indicator of gender balance and influenced by mortality differences, migration and social customs.

The movement of people from one place to another for a considerable period or permanently, usually explained by push factors at the origin and pull factors at the destination.

The rising proportion of a country's population living in towns and cities, together with the spread of urban ways of living; it is measured as the percentage of people classed as urban.

Site is the actual ground a settlement occupies, such as a river terrace or hill; situation is its position relative to routes, rivers and resources, and both help explain growth or decline.

Work that provides services instead of goods, including trade, transport, banking, education, health care and tourism; such employment usually grows as incomes and cities expand.

The tongue of land lying between two rivers that converge or run close together; the word is widely used for the interfluves of the rivers crossing the northern plains of India.

A leached, iron-rich soil formed under heavy seasonal rainfall with alternating wet and dry spells; it hardens on exposure and needs fertiliser, and occurs in parts of Assam and the Deccan.

A scheme in which a river is used for several purposes at once, such as irrigation, hydel power, flood control, navigation, water supply and fisheries, through dams, canals and embankments.

The summer crop season of India, sown with the arrival of the monsoon in June and July and harvested in autumn; rice, jute, maize and cotton are typical kharif crops.

The package of high-yielding seed varieties, chemical fertiliser, assured irrigation and machinery adopted in India from the mid-1960s, which sharply raised wheat and rice output.

A composite measure combining life expectancy, education and per capita income, used to compare welfare between Indian states and between countries rather than output alone.

The high-speed, multi-lane highway network linking Delhi, Mumbai, Chennai and Kolkata, forming the main frame of India's national highway system and carrying a large share of freight.

A river route developed for regular freight and passenger transport; National Waterway 2 follows the Brahmaputra from Dhubri to Sadiya and is central to Assam's water transport plans.

A line on a map joining all points at the same height above sea level; closeness of contours shows steepness of slope and their shapes reveal valleys, ridges and plateaus.

The fixed relation between a distance measured on a map and the real distance on the ground, stated as a representative fraction, a written statement or a graduated bar.

Gathering information about the Earth's surface using sensors mounted on aircraft or satellites, which record reflected or emitted radiation without touching the objects studied.

A computer system that stores, links, combines and displays spatial data in layers tied to location, allowing maps to be queried and analysed for planning and management.

A line or narrow belt drawn across an area along which observations are recorded during field study, so that changes in soil, vegetation, land use or slope can be compared.

A written set of questions used to collect information directly from respondents; careful wording, pre-testing and a proper sample are needed for the replies to be reliable.