Geography Dictionary

Backwash – used in both physical and human geography

• in physical geography, the movement of water down a beach to the sea after having run up the beach in the swash.
• in human geography, the movement of resources from periphery to core through a series of circuits: capital concentrates in the core, depriving the periphery and reducing wealth generation there; migration tends to take younger, more employable workers to the core leaving older, less productive workers in the periphery; lack of investment in services, amenities and infrastructure further widen the gap.

Bacteria – a class of organisms known as Prokaryotes in which the cell has no nucleus. They are single-cell microbes which can be found virtually everywhere. They ‘eat’ almost anything which lends them an enormous variety of very useful functions, although they can also be responsible for sickness. Geographers may be interested in the role they play in health patterns, especially in the ELDW, or in soil formation, or many other topic areas.

Bahada – gently sloping plain formed when a number of alluvial fans exiting closely spaced wadis in desert areas coalesce into a larger feature.

Balance of payments – net sum of a country’s income from and expenditure on foreign trade which can run to a surplus or a deficit.

Balance of trade – the net sum of imports and exports of visible goods. Forms part of the balance of payments along with the same calculation for invisibles.

Bankfull discharge – the maximum discharge that a particular river channel is capable of carrying without flooding.

Baobab tree – a pyrophitic tree found in savannah areas. It has an enormous trunk which stores water and tiny leaves to minimize evapotranspiration.

Bar – see sand bar.

Barchan – crescent-shaped sand dune which form in desert areas experiencing generally constant winds. The ‘horns’ of the crescent point downwind, having moved ahead more rapidly, where they become sheltered and stable. Sand moves up the windward side and collapses down the leeward side which is steeper. This net movement of sand from the windward to the leeward side causes the dune to move forwards.

Bar chart – bars of equal width placed within perpendicular axes and used to represent varied amounts or frequencies through variations in length.

Barrage – a dam or barrier with adjustable gates and sluices built across an estuary in order to harness tidal energy.

Barrier beach – low-lying, bar-shaped sand and/or coral island lying parallel to but slightly away from a coastline. The landward side tends to be marshy or a lagoon.

Basal sapping – the undercutting and retreat of a slope caused when erosion and/or weathering are concentrated at its base.

Basal slipping – during summer time in warmer glacial areas, limited melting lubricates the base of the glacier allowing it to move more freely. Movement increases pressure, raising temperature and allows further melting as the ice reaches its pressure melting point.

Basalt – an igneous rock, fine-grained and glass-like, formed by rapidly cooled lava often under water.

Base flow – that portion of river discharge derived from groundwater flow.

Base level – the lowest elevation to which erosion can take place. Usually sea-level but could be lower if a river drains into an inland sea or lake whose level is below sea-level.

Basic volcano – where low viscosity, extremely hot lava flows from a vent it will spread rapidly to form a shallow sloped, low altitude cone.

Batholith – a massive intrusive volcanic feature. Magma forces its way into the crust but becomes trapped and solidifies into rock e.g. granite.

Battery farming – intensive, commercial livestock (usually poultry or cattle) production where animals are reared in cages and fed and watered automatically to reduce the per unit cost. May also include hormone treatment.

Bay – a curved indent to the coastline, usually created by greater erosion rates than neighbouring parts of the coast. Bays often contain beaches and provide an area of shelter both for boats and for settlements.

Beach – accumulation of sand and shingle material at a coast or at the fringes of a body of water due either to low energy brought about by sheltered conditions or due to an excess of sediment.

Beach depletion – net loss of sand and/or shingle from a beach due to reduced replenishment while removal processes such as longshore drift continue unabated. Natural replenishment rates are thought to have slowed as sea-levels have risen, river loads have reduced, beaches have stabilized and humans have dredged offshore sediments.

Beach nourishment – human replenishment of depleted beaches using material from land pits or dredged deposits. Beach material may be allowed to move by longshore drift before being returned to where it started.

Beaufort scale – a scale for wind speed, and therefore strength, based on observable effects.

Bedding plane – the boundary between adjacent layers or strata in a sedimentary rock.

Bedload – larger load which is unable to move in suspension but is transported by saltation and traction.

Bedrock – solid rock underlying other surface materials.

Benioff Zone – boundary between an oceanic plate undergoing subduction beneath a continental plate. Characterized by earthquakes and the melting of the oceanic plate.

Bergeron-Findeison process – a theory of raindrop formation. At temperatures between -5°C and -25°C both water droplets and ice crystals exist in the same space. Vapour is sublimated onto the ice crystals and the deficit in vapour is compensated by the evaporation of the water droplets leading to further sublimation and thus growth of the ice crystals. These may coalesce into snowflakes which then overcome gravity and fall. When air temperatures at the surface are greater than zero the flakes melt into water drops before they land.

Bergschrund – a large crevasse at the upper portion of a corrie glacier, close to the back-wall.

Berm – a low ridge towards the rear of a beach marking the uppermost level that waves reached during the previous high tide.

Best-fit line – a line drawn on a scatter-graph, as close to all the points as possible, which thus indicates any trend in the pattern. Points that are very disparate may not provide an opportunity to draw a best-fit line and thus show no trend or correlation. If the points all lie on the line, the correlation is perfect.

Beta index – a measurement of connectivity using the formula

                                    β =  e   

                                           v

where e is number of edges and v is number of vertices. The higher the value of β the greater the connectivity.

Bias – distortion in sampling which means that the sampled data does not represent the population which it is meant to represent.

Bid-rent theory – the idea that land is acquired by the highest bidder which is in turn a function of the user who can make the most profit from the site. Usually related to accessibility.

Bifurcation ratio – in a drainage basin, the relationship between the streams of one order of magnitude and those of the next highest order, obtained by dividing the number of lower order streams with the number of the higher order. The lower the number the greater the risk of flooding. (see also stream order)

Bilharziasis – disease caused by a parasitic worm which enters the human body by penetrating the skin while swimming/bathing/working in infected waters. Mostly found in tropical areas of Africa, Asia and South America. Causes particular problems for the liver and kidneys by mass production of eggs. Leads to anemia and lethargy but not usually directly fatal. At least 200 million infected and a further billion under threat.

Biodiversity – the range of species in a particular area.

Biofuel – fuel derived from biomass. In primitive form this could mean burning firewood. More usually used to refer to gas or alcohol products derived from biomass for burning either to produce electricity or as vehicle fuels.

Biogas – a form of biofuel where methane gas is obtained from decomposing biomass for energy use.

Biological control – use of natural organisms to fight weeds and pests in agriculture.

Biomass – total amount of organic material.

Biome – large-scale natural community named for its dominant vegetation.

Biotechnology – use of biological knowledge and research to developing technologies especially in pharmaceutical areas.

Biotic factors – the influence of living organisms on the growth and distribution of plants such as shade provided by leaves or seed dispersal by animals.

Bi-polar test – the provision of two opposite views between which strength of feeling can be measured e.g. a scale of one to five in which one represents negative feelings and five positive.

Birth control programme – a systematic approach to controlling the birth rate in a particular area, usually at the national or sub-national level in an ELDC.

Birth rate – number of live births per thousand people per year.

Blizzard – a heavy snowstorm combined with high speed wind.

Blockfield – extensive area of large angular rock fragments in periglacial regions. 

Blocking anticyclone – when an anticyclone breaks northwards to 50°-70°N where it can come to rest for several weeks and divert other, more usual weather systems, off their usual paths leading to extended periods of clear, dry weather.

Blowout depression – a small, shallow bowl-shaped feature created by wind erosion in coastal and arid areas.

Bluff – slope created by lateral river erosion causing the retreat of interlocking spurs. 

B.O.D. – biological oxygen demand – milligrams of dissolved oxygen per litre of water at 25°C required to allow decomposition of organic material in polluted water.

Bog – waterlogged, spongy ground forming in cooler, high-rainfall areas. Only smaller plants are able to grow and their decomposition is very slow leading to peat soil formation. Often found in upland areas.

Boreal – most usually used to mean northern in reference to latitudes 45°-75°N and in association with the largely coniferous forests found here.

Boserup, Ester – a Danish economist who suggested that the ideas of Malthus regarding the relationship between population and resources, particularly food, did not hold because technological development allowed resource production to support larger populations than previously thought possible, or ‘necessity is the mother of invention’. More recent studies suggest the reverse may be true.

Bottomset beds – layers of sediment in a delta found furthest from the river mouth and formed from flocculated clay particles.

Bottom-up – ideas, initiatives or developments originating in and flowing from the lower levels of a hierarchy further up the hierarchy.

Boulder – a size-classification of rock pieces. Boulders should be lumps of rock at least 200 mm in diameter.

Boulder clay – see till.

Bourne – a seasonal river which flows in normally dry valleys during wetter periods of the year.

B.P. – before present – an alternative, more accurate, means of identifying past years.

Brackish – a slightly saline environment where sea water inputs are moderated by an inflow of freshwater.

Braiding – when a river is forced to divide into multiple channels which interlink with each other. A feature of rivers with high loads and occupying wide, flat areas of low relief.

Brandt Report – produced in 1980 by a commission headed by Willy Brandt, former West German Chancellor. Its focus was the difference in social, economic and political well-being between the EMDW and ELDW, then referred to as the North and the South respectively. It concluded that both sets of countries were interdependent on each other, and neither should raise barriers against the other.

Breaker – an overextended wave which then collapses sending water forward. Occurs when sea waves enter shallow water and are slowed at their base by friction.

Breaking point – in gravity models, the point at which customers prefer to travel to one centre rather than another.

Break of bulk – a site where cargo is broken down from a large, bulk carrying unit, to smaller scale units, usually involving a change in the mode of transport.

Breakpoint bar – a sand bar parallel to the coast which is located approximately at the point where waves begin to break.

Breccia – a sedimentary rock made up of large, angular grains which have been cemented together.

Bridging point – a site factor. Early settlements were often built where a river was shallow enough to be forded. As bridge building improved, more points on rivers were suitable for building crossings.

Bronze Age settlement – settlements, or evidence of settlement, dating between 3900BP to 2500BP.

Brown earth – type of soil associated with northern Europe in deciduous woodland areas. High leaf litter in autumn provides plenty of material for decomposition into a rich humus which is mixed into the soil by soil fauna creating the rich brown colour.

Brownfield site – a site, either derelict or holding very old buildings, which could be redeveloped for new uses.

Burgess, Earnest – an American sociologist who proposed the concentric-ring model of urban land use. Based on Chicago, the model was developed by applying ecological rules and relationships to the behaviour of people in creating their urban areas.

Business cycle – regular pattern of ‘boom and bust’ upturns and downturns in economic demand and output repeating every 5-7 years.

Business park – purpose-built or redeveloped areas for companies requiring office space rather than industrial space. Some high-tech production may also appear. Characterized by low-rise, highly modern units, well-spaced and landscaped. May also include leisure and convenience amenities for employees.

Bustee – the name for a shanty town in India.

Buys Ballot – a Dutch scientist. Proposed in 1857 that, if you stand with the wind to your back in the Northern hemisphere, low pressure lies to your left. Vice versa in the Southern hemisphere.

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