Dictionary of Geographical terms Using the Dictionary commercial agriculture, subsistence agriculture anthracite A hard form of coal with a high carbon and peasant agriculture. See also agribusiness. content and few impurities. Geographical terms in the aid The provision of fi nance, personnel anticline An arch in folded strata; the opposite of and equipment for furthering economic syncline. See fold. dictionary are arranged development and improving standards of living anticyclone An area of high atmospheric pressure alphabetically. Bold words in in the Third World. Most aid is organized by with light winds, clear skies and settled weather. an entry identify key terms which international institutions (e.g. the United Nations), In summer, anticyclones are associated with warm are explained in greater detail by charities (e.g. Oxfam) (see non-governmental and sunny conditions; in winter, they bring frost organizations (NGOs); or by national governments. and fog as well as sunshine. within separate entries of their Aid to a country from the international institutions own. Important terms which is called multilateral aid. Aid from one country to do not have separate entries are another is called bilateral aid. shown in italic and are explained air mass A large body of air with generally the same temperature and moisture conditions throughout. in the entry in which they occur. Warm or cold and moist air masses usually develop over large bodies of water (oceans). Hot or cold and dry air masses develop over large land areas (continents). anticyclone alluvial fan A cone of sediment deposited API (application programming interface) A set A at an abrupt change of slope; for example, where of interfaces, methods, procedures and tools used abrasion The wearing away of the landscape by a post-glacial stream meets the fl at fl oor of a to build or customise a software program. rivers, glaciers, the sea or wind, caused by the load U-shaped valley. Alluvial fans are also common aquifer See artesian basin. of debris that they carry. See also corrasion. in arid regions where streams fl owing off arable farming The production of cereal and root abrasion platform See wave-cut platform. escarpments may periodically carry large loads of crops – as opposed to the keeping of livestock. accuracy A measure of the degree of correctness. sediment during fl ash fl oods. arc A coverage feature class representing lines and acid rain Rain that contains a high concentration polygon boundaries. of pollutants, notably sulphur and nitrogen oxides. archipelago A group or chain of islands. These pollutants are produced from factories, arctic circle Imaginary line that encircles the North power stations burning fossil fuels, and car Pole at latitude 66º 32'N. exhausts. Once in the atmosphere, the sulphur arête A knife-edged ridge separating two corries and nitrogen oxides combine with moisture to give in a glaciated upland. The arête is formed by the sulphuric and nitric acids which fall as corrosive progressive enlargement of corries by weathering rain. and erosion. See also pyramidal peak. alluvial fan administrative region An area in which organizations carry out administrative functions; alluvium Material deposited by a river in for example, the regions of local health authorities its middle and lower course. Alluvium comprises and water companies, and commercial sales silt, sand and coarser debris eroded from the regions. river’s upper course and transported downstream. adult literacy rate A percentage measure which Alluvium is deposited in a graded sequence: arête shows the proportion of an adult population able coarsest fi rst (heaviest) and fi nest last (lightest). artesian basin This consists of a shallow syncline to read. It is one of the measures used to assess the Regular fl oods in the lower course create extensive with a layer of permeable rock, e.g. chalk, level of development of a country. layers of alluvium which can build up to a sandwiched between two impermeable layers, e.g. aerial photograph A photograph taken from considerable depth on the fl ood plain. clay. Where the permeable rock is exposed at the above the ground. There are two types of aerial alp A gentle slope above the steep sides of surface, rainwater will enter the rock and the rock photograph – a vertical photograph (or ‘bird’s- a glaciated valley, often used for summer grazing. will become saturated. This is known as an aquifer. eye view’) and an oblique photograph where the See also transhumance. Boreholes can be sunk into the structure to tap the camera is held at an angle. Aerial photographs water in the aquifer. are often taken from aircraft and provide useful asymmetrical fold Folded strata where the two information for map-making and surveys. alp limbs are at diff erent angles to the horizontal. Compare satellite image. analysis The examination of the constituent parts aff orestation The conversion of open land to of a complex entity. forest; especially, in Britain, the planting of anemometer An instrument for measuring the coniferous trees in upland areas for commercial velocity of the wind. An anemometer should be asymmetrical fold gain. Compare deforestation. fi xed on a post at least 5 m above ground level. The agglomerate A mass of coarse rock fragments or wind blows the cups around and the speed is read atlas A collection of maps. blocks of lava produced during a volcanic eruption. off the dial in km/hr (or knots). atmosphere The air which surrounds the Earth, agribusiness Modern intensive farming which and consists of three layers: uses machinery and artifi cial fertilizers to increase the troposphere (6 to 10km from the Earth’s surface), yield and output. the stratosphere (50km from the Earth’s surface), and Thus agriculture resembles an industrial process anemometer the mesosphere and ionosphere, an ionised region of in which the general running and managing of the annotation Labels in the form of text or graphics rarefi ed gases (1000km from the Earth’s surface). farm could parallel that of large-scale industry. that can be individually selected, positioned or The atmosphere comprises oxygen (21%), nitrogen agriculture Human management of the stored in a database. (78%), carbon dioxide, argon, helium and other en vironment to produce food. The numerous antarctic circle Imaginary line that encircles the gases in minute quantities. forms of agriculture fall into three groups: South Pole at latitude 66º 32'S. attrition The process by which a river’s load is eroded through particles, such as pebbles and Batholiths may eventually be exposed at the Earth’s of habitats, from the highest mountains to the boulders, striking each other. surface by the removal of overlying rocks through deepest oceans. weathering and erosion. birth rate The number of live births per 1000 people in a population per year. B bituminous coal Sometimes called house coal – a backwash The return movement of seawater off the medium-quality coal with some impurities; the beach after a wave has broken. See also longshore typical domestic coal. It is also the major fuel drift and swash. source for thermal power stations. bar graph A graph on which the values of block mountain or horst A section of the Earth’s batholith a certain variable are shown by the length crust uplifted by faulting. Mt Ruwenzori in the of shaded columns, which are numbered bay An indentation in the coastline with a headland East African Rift System is an example of a block in sequence. Compare histogram. on either side. Its formation is due to the more mountain. rapid erosion of softer rocks blowhole A crevice, joint or fault in coastal rocks, enlarged by marine erosion. A blowhole often leads from the rear of a cave (formed by wave action at the foot of a cliff ) up to the cliff top. As waves bar graph break in the cave they erode the roof at the point barchan A type of crescent-shaped sand dune of weakness and eventually a hole is formed. Air formed in desert regions where the wind direction bay and sometimes spray are forced up the blowhole to is very constant. Wind blowing round the edges of beach A strip of land sloping gently towards the sea, erupt at the surface. the dune causes the crescent shape, while the dune usually recognized as the area lying between high may advance in a downwind direction as particles and low tide marks. are blown over the crest. beach bearing A compass reading between 0 and 360 degrees, indicating direction blowhole barchan of one location from another. bluff See river cliff . barograph An aneroid barometer connected to an boreal forest See taiga. arm and inked pen which records pressure changes boulder clay or till The unsorted mass of debris continuously on a rotating drum. The drum dragged along by a glacier as ground moraine and usually takes a week to make one rotation. dumped as the glacier melts. Boulder clay may barometer An instrument for measuring be several metres thick and may comprise any atmospheric pressure. There are two types, bearing The bearing from A to B is 110º. combination of fi nely ground ‘rock fl our’, sand, the mercury barometer and the aneroid barometer. Beaufort wind scale An international scale of wind pebbles or boulders. The mercury barometer consists of a glass tube velocities, ranging from 0 (calm) to 12 (hurricane). breakwater or groyne A wall built at right angles containing mercury which fl uctuates in height as bedrock The solid rock which usually lies beneath to a beach in order to prevent sand loss due to pressure varies. The aneroid barometer is a small the soil. longshore drift. metal box from which some of the air has been bergschrund A large crevasse located at the rear of removed.