WBCHSE HS Geography flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Peneplain

A nearly level, gently undulating surface produced by long-continued erosion near base level. It is the end stage of the Davisian cycle, marked by residual hills called monadnocks.

Moraine

Any accumulation of unsorted glacial debris, including clay, sand, gravel and boulders, deposited directly by ice. It is named by position as lateral, medial, terminal or ground moraine.

Barchan dune

A crescent-shaped sand dune whose horns point downwind, formed in arid areas with limited sand supply and a constant wind direction. The steep slip face lies on the lee side.

Epicentre

The point on the Earth's surface vertically above an earthquake focus. Seismic waves reach it first, so it usually records the strongest shaking and the highest intensity.

Lapse rate

The rate at which temperature falls with height in the troposphere, averaging about 6.5 degrees C per kilometre. It explains why hill stations are cooler than the neighbouring plains.

ITCZ

The equatorial trough of low pressure where the northeast and southeast trade winds converge. It shifts with the overhead sun and governs the wet and dry seasons of tropical monsoon lands.

Coriolis force

An apparent force caused by the Earth's rotation that deflects winds and currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, strongest at the poles.

Koppen climate classification

A climate classification based on monthly temperature and rainfall averages and their seasonality, using letter codes such as Af, Aw, BWh, Cs and Cfa to define climatic types.

Spring tide

The extra-high tide occurring at new moon and full moon, when the sun, moon and Earth lie in line so that solar and lunar tidal forces reinforce each other.

Thermocline

A layer in the ocean, roughly 100 to 1000 metres deep, where temperature falls rapidly with depth. It separates warm surface water from cold deep water and inhibits vertical mixing.

Upwelling

The upward movement of cold, nutrient-rich water from depth to the surface, caused by offshore winds or divergence. It supports highly productive fisheries, as off the coast of Peru.

Ecological pyramid

A diagram showing the number, biomass or energy of organisms at each trophic level. Energy pyramids are always upright because about 90 percent of energy is lost at each transfer.

Biodiversity hotspot

A region with exceptionally high numbers of endemic species that has already lost at least 70 percent of its original vegetation. Four such hotspots extend into India, including the Western Ghats.

Climax community

The relatively stable final stage of ecological succession, in equilibrium with the regional climate, in which species composition remains broadly unchanged until a disturbance occurs.

Demographic transition model

A model describing the shift from high birth and death rates to low ones as a country develops, passing through a stage of rapid natural increase before population stabilises.

Sex ratio

The number of females per 1000 males in a population. India recorded 943 and West Bengal 950 in the 2011 Census; the figure reflects social attitudes and female survival.

Primate city

A city disproportionately larger than the second-ranked city of the same country, concentrating political, economic and cultural functions, for example Bangkok in Thailand.

Dependency ratio

The ratio of persons aged under 15 and over 64 to those aged 15 to 64, usually expressed per 100 workers. It shows how many dependants each working person supports.

Von Thunen model

A model of agricultural land use around an isolated town in which perishable and bulky products are grown nearest and extensive grains and livestock farthest, because transport cost rises with distance.

Kharif season

The summer cropping season, sown with the onset of the southwest monsoon in June and July and harvested in September and October. Crops include rice, jute, cotton, maize and groundnut.

Special Economic Zone

A demarcated area with duty-free imports, tax concessions and simplified procedures, designed to attract foreign investment and to boost export-oriented production and employment.

Damodar Valley Corporation

The Damodar Valley Corporation, set up in 1948 on the Tennessee Valley model, manages multipurpose dams such as Tilaiya and Maithon for flood control, irrigation, power and navigation.

Rarh region

The undulating laterite and red-soil upland of western West Bengal, lying between the Chota Nagpur plateau edge and the Bhagirathi and drained by the Damodar, Mayurakshi and Kangsabati.

Dooars

The humid, forested foothill tract of northern West Bengal between the Terai and the Himalayan foothills, drained by the Tista and its tributaries and important for tea plantations.

Biochemical oxygen demand

The oxygen consumed by microbes to decompose organic matter in a water sample over five days at 20 degrees C. High values indicate heavy organic pollution and low water quality.

Sendai Framework

The 2015 to 2030 global agreement on disaster risk reduction, with seven targets aiming to reduce mortality, affected persons and economic losses and to strengthen preparedness and early warning.

Vulnerability

The conditions of exposure and susceptibility that make people or assets likely to be harmed by a hazard. Risk is often expressed as hazard times vulnerability divided by capacity.

Contour interval

The constant vertical distance between two successive contour lines on a topographic map. A small interval indicates gentle slopes; a large interval indicates steep terrain.

Choropleth map

A thematic map in which administrative units are shaded or patterned in proportion to the value of a variable, such as population density, using graded class intervals.

Vector data model

A GIS data model storing features as points, lines and polygons with explicit coordinates. It suits boundaries and networks well but is less efficient for continuous surfaces.

Remote sensing

The acquisition of information about the Earth's surface without physical contact, using sensors on satellites or aircraft that record reflected or emitted electromagnetic radiation.

Standard deviation

A measure of dispersion equal to the positive square root of the variance. A small value means values cluster near the mean; a large value means they are widely spread.