Common Geographical Terms : Letter C

Caldera A large basin shaped volcanic crater is called caldera, Caldera forms in one of the followin.& tWe ways: (a) by destruction of the upper part of the vokanic cone by an eruption, of great force

Canyon (Canon) Canyon or canon is the name given to a deep valley/gorge with steep near-vertical sides. It forms by river action, mostly in arid and semi-arid areas, where a river is fed with water from a, distant source. In qmyon, the depth exceeds ttw width consid­erably. The most striking canyons are produced in areas of horizontally bedded strata, e.g., the Grand Canyon in USA
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Catadasis refers to rock deformation accompa­nied by fracture and rotation of mineral grains. A rock formed in this way is termed a cataclasite.

Catchment Area A catchment area is the area from which a single river system collects its water. In other words, it is the area from where the river and its tributaries get most of their water. Water may be in the form of ice, snow or rain. The boundary of a catchment area is defined as the watershed.

Chaparral The term chaparral refers to a form of vegeta­tion ctominated by thick-growing evergreen oaks and other trees, with aromatic shrubs. Chaparral occurs in California (USA) and Mexico, where there is a Mediter­ranean type of climate. It has evolved in response to mild wet winters and summer drought.

Chelation The process by which rQd~s and soils decompose or disintegrate through the action of organisms or organic substi\nees is called chelation. The organic com­P°1.U\(is, known as chelating agents, are extracted from the litter layer by water passing down through it. Chelating agents are richest in heath plants and conifer needles. Chelation plays a major part in the soil process of podzolisation.

Cheluviation Cheluviation is the cor'bination of chelation and eluviation. In cheluviation, water containing organic extracts combines with met{\Uic cations in the soil to , form a chelate. ThQ chelate (a sesquioxide-rich solution) then rn.~W~ downward through the soil profile (hence eluviation).

Chemozem (Tschemosem) Chernozem is a black or dark­brown zonal soil that is rich in humus and contains lime. The name chernozem is derived from the Russian term
tschernosem meanin 'black earth'. Hence chernozem is also called black earth. This soil type is found in a blt tending from Manchuria in China through Russia into Ukraine and into Romania. and Hungary. It is a fertile ,Qit \\no is often used to support cereal crop.

Chestnul Soil Chestnut soil is a zonal (pedocal) soil found on the steppes of the former USSR, the pampas of Argentina, the Great Plains of the USA and the South African veld. Hence, it is a soil of mid~latltude grasslands that occur in drier regions than chernozems. Further, the horizonation of thQ chestnut soils is not as clearly marked i,\s that of the chernozems and it does not develop to such depths. The parent material for chestnut soil is frequently loess.

Chinook Chinook is a warm, dry south-westerly wind which blows down the eastern slopes of the RocKies in parts of North America (specially in Canada and the USA). It is adiabatically warmed and often causes a large rise in temperature. In spring,
Chinook, which is similar to fohn, leads to rapid snowmelt and subsequent avalanches. .

Circum-Pacific Belt The Circum-Pacific belt is a seismic b-elt, which girdles Pacific Ocean. World's 75 per cent earth­quakes occur in this belt. This belt is also characterised by many active volcanoes. Hence. it is popularly called the Ring of Fire. It mostly coincides with the margins of tectonic plates.

Cirque (Corrie, cwm) A deep amphitheatre-shaped rock basin with steep sides and an opening downstream is called cirque. Found in glaciated upland areas, cirques originate as small hollows where snow accumulates. The characteristic shape of

cirques is a result of erosion on the headwall and the rotational slip of the ice within the concave floor of the hollow.

Cirque Glacier A small glacier occupying a glacially eroded armchair-shaped hollow or cirque is called cirque glacier. Cirque glacier may be contained entirely within the reck basin or it may extend outwards beyond the tip of the cirque. It is characterised by a rotational slip.

Cirrocumulus It is a type of cloud occurring between 5,000 and 13,700 m, i.e., at high altitudes. It is white in colour occurring in thin sheets or layers without shading. Due to its resemblance to fish scales, it is sometimes krt°wn as "mackerel sky".
Cirrostratus Cirrostratus is a high altitude cloud Dccuring between 5,000 m and 13,700 m. It is whitish in colour. The ,cloud produces solar or lunar halo phenomenon.
Cirrus A cloua, white in colour, occuring as silky, fibrous brands or wisps, is called cirrus cloud. Its base can occur between 5,000 m and 13,700 m, Le., at high altitudes. Long-d~awn out wisps known as "maires' tails" are produced by strong windt in the upper atmosphere.
Cliff A very steep or vertical rock face is called cliff. Cliffs have different forms depending upon factors such as rock type, resistance to erosion, and the presence of bands of weakness. Sea cliffs are formed by wave» undercutting the rock causing its eventual collapse, Near vertical cliffs can also be formed in well-jointed rocks, but where wave-attack k"5 diminished and the cliff foot has been abandoned. Cliffs are a!;>o found in inland areas and in mountainous regions.
Climate The average weather conditions at a specific pla~ over a lengthy period of time (usually at least 30 years) is called climate. The main elements of clhnateare
temperature, atmospheric pressure, wind and humidity. The climate of a particular region is determined by (i) latitude and the tilt of the earth's axis; (ii) the distribution of land and sea and proximity of ocean currents; (iii) the location of the area in relation to the main circulation belts of the eiirthi and (iv) the altitude and topography of the area.
Climatograph A climatograph 1$ a circular graph depicting seasonal mean-temperature changes plQtted on a monthly basis.
Climograph (Climatogram) A climograph is a graphic diagram to illustrate the general climatic character of a particular place. The diagram is produced by plotting two climatic elements (usually temperature and humid­ity) of a place. The result.ant shape of the graph indicates the character of the climate at that place. The term climograph was first used by T. Grifith Taylor.


Crust The crust is the outer most shell of the earth. Lying above the Mohorovicic discontinuity and varying in thickness, it comprises two dominant groups of rocks: sial (continental crust) and sima (oceanic crust). The crust is also sometimes referred to as duricrust.

Cryopedology The scientific study of frost action in soils and the resulting structures is called cryopedology.

Crystalline Rock A rock formed by the process of crystallisation is called crystalline rock. Crystalline rocks include igneous and metamorphic rocks. In an igneous rock, the rate of cooling of magma and the order in which the minerals are crystallised determine the shape and size of crystals. In metamorphic rocks, the shape and size of crystals depends on the mineral itself.

Cuesta Cuesta is a Spanish term that has been widely adopted to describe a ridge with a steep scarp slope (escarpment) and a comparatively dip slope. Cuesta closely reflects the structure of the underlying rocks. It is formed by the differential erosion of gently dipping stra ta.

Cumulus Cumulus is a type of detached, dense cloud. It is greyish in colour when viewed from beneath, but brilliant white where sunlit and seen from the side. In elevation, this cloud type varies between 460 m and 2,000 m. The base of cumulus cloud is horizontal. Cumulus clouds occur mainly in summer and are caused by convection.
Current The current is defined as the permanent or seasonal' flow of water in a defined direction in the surface water of an ocean, e.g., North Atlantic Drift, Labrador Current, Benguela Current, etc.
Cyclone and Anti-Cyclone Cyclone is a system of low atmospheric pressure in the centre. There are two types of cyclone: the tropical cyclone and the temperate cyclone. Tropical cyclone OCCUlS in the tropical regions, such as Indian Ocean, Indonesia and Australia. In tropical cyclone, the wind rotates in an anti-clockwise direction in Northern Hemisphere and in a clockwise direction in Southern Hemisphere. It is associated with very high speed winds with torrential rainfall. Temper­ate cyclone occurs in temperate latitudes. It is now commonly referred to as depression or low.
Anti-cyclone is a system of high atmospheric pressure in the centre and decreasingly low pressure towards the periphery of the system. Air movement is clockwise in Northern Hemisphere and antklockwise in Southern Hemisphere. The associated weather is settled and stable. Two types of anti-cyclone are: (i) cold anti­cyclone (e.g. over Canada and Siberia), and (ii) warm anti-cyclone (e.g. over sub-tropical high pressure belt).
Cyclothem The term cyclothem refers to a series of sedimentary beds deposited during a single cycle of sedimentation. It is indicative of changing environmen­tal conditions.
Cymatogeny The term cymatogeny refers to large scale tectonic warping of the crust to produce a type of basin­swell structure. In basin-and-swell structure, the crests
of the swells (domes) collapse to form graben (rift valley).