Glossary of geography terms (A–M)

This glossary of geography terms is a list of definitions of terms and concepts used in geography and related fields, including Earth science, oceanography, cartography, and human geography, as well as those describing spatial dimension, topographical features, natural resources, and the collection, analysis, and visualization of geographic data. It is split across two articles:


 * This page, Glossary of geography terms (A–M), lists terms beginning with the letters A through M.
 * Glossary of geography terms (N–Z) lists terms beginning with the letters N through Z.

Related terms may be found in Glossary of geology, Glossary of agriculture, Glossary of environmental science, and Glossary of astronomy.

A
absolute location: The particular of a point on Earth's surface that can be expressed by a grid reference such as and.

accessibility: A locational characteristic that permits a place to be reached by the efforts of those at other places.

accessibility resource: A naturally emergent landscape form that eases communication between areas.

acme: See.

acre (ac): A unit of area traditionally defined as the area of a plot of land one (66 feet) by one furlong (660 feet), equivalent to 43560 sqft, or about 0.40.

active volcano: A that is currently erupting, or one that has erupted within the last 10,000 years (the Holocene) or during recorded history.

adret: The sunny, warm of a hill or mountain, as opposed to the or shady side.

affluent: See.

agricultural geography: A sub-discipline of geography which studies the spatial relationships between humans and agriculture, as well as the cultural, political, and environmental processes that lead to parts of the Earth's surface being transformed into agricultural landscapes through activities.

alluvial fan: A distinctly triangular or fan-shaped deposit of sediment transported by water, often referred to as. Alluvial fans usually form at the base of, where high-velocity rivers or streams meet a relatively flat area and lose the energy needed to carry large quantities of sediment, which ultimately spreads out in all available directions. They tend to be larger and more obvious in arid regions.

alluvial plain: A wide, flat, gently sloping created by the long-term of  from one or more  flowing from  regions, and typically characterized by various  landforms such as,, and. Alluvial plains encompass the larger area over which a river's has shifted through geological time.

alluvial soils: Soils deposited through the action of moving water. These soils lack and are usually highly fertile.

alluvium: Clay, silt, gravel, or similar detrital material by flowing water.

alpine: Characteristic of or resembling the European Alps, or any other high-elevation or environment (especially one deeply modified by  erosion so as to contain characteristic  such as,, etc.), in , climate, or ecological communities.

altitude: The height of an object in the above. The term is sometimes used interchangeably with.

amphidromic point:

A geographical location where there is little or no, i.e. where the is zero or nearly zero because the height of does not differ significantly at  and, and around which a tidal crest circulates once per tidal period (approximately every 12 hours). The tidal amplitude increases, though not uniformly, with distance from these points. Amphidromic points are the consequence of resonance phenomena which occur when obstructing landmasses reflect tidal bulges back and forth across oceanic basins; their precise locations, usually in the near the center of the basin, depend largely on the surrounding  and, and also vary slightly with winds, currents, and the positions of the Sun and the Moon. There are at least a dozen well-defined amphidromic points across the Earth's oceans.

anastomosing stream:

A or composed of multiple, branching, interconnected, coexisting  that enclose floodbasins on, usually formed when a slow-moving river encounters  that divert its flow, creating new channels on the floodplain.

anecumene:

The part of the Earth's surface which is uninhabited and/or uninhabitable by human beings. Contrast.

angle of repose: The steepest angle of descent or dip, relative to the horizontal plane, at which a mass of loose, freely movable material such as sand or unconsolidated rock debris can remain stationary, i.e. without sliding downward, despite the pull of gravity.

Antarctic: The region of the Earth that is south of the.

Antarctic Circle: The southernmost of the Earth's two of, south of which the sun appears above the for 24 continuous hours at least once per year (and is therefore visible at midnight) and also appears at least partially below the horizon for 24 continuous hours at least once per year (and is therefore not visible at noon). Its latitude is approximately 66°33′47.1″ south of the. Contrast.

antecedent stream:

A or other that existed before the present form of the surrounding land surface was established and which maintains its original course and pattern despite changes in the local geology or. For example, a landscape featuring a river with a dendritic drainage pattern may be altered by gradual, localized, but the river may be sufficiently powerful to erode through the new obstructions as rapidly as they are formed, carving a rather than being redirected, and thereby preserving its dendritic pattern even though it now flows over a landscape that typically produces very different drainage patterns. Compare.

anthropization: The conversion of open spaces, landscapes, and natural environments by human action.

anthropogenic: Of or relating to anthropogeny, the scientific study of the origins of human beings. Having an origin in human activity; caused by or attributable to humans.

anti-dip stream: A stream flowing in a direction approximately opposite to that of the of the underlying surface rocks. It is frequently, though not necessarily, an stream.

anticline: A geological that has an arch-like convex shape and its oldest near its center, often visible at the Earth's surface in exposed. Contrast.

antimeridian: The of that is directly opposite or  to a given meridian, i.e. the imaginary line that is exactly 180 degrees of longitude distant from the given meridian. Together, a meridian and its antimeridian form a that passes through the geographic poles. The 180th meridian in particular, i.e. the meridian of longitude that is exactly 180 degrees both east and west of the, with which it forms a great circle dividing the Earth into the and. The 180th meridian is used as the approximate basis for the because it mostly passes through the open waters of the Pacific Ocean.

antipodes: Any pair of points on the Earth's surface that are diametrically opposite to each other, such that a straight line connecting them would pass through the Earth's center. Such points are as far away from each other as possible, with the between them being approximately 20000 km.

anywhere fix: A geographic position which a receiver is able to calculate without requiring information about its own location or the local time.

apogean tide: The when the Moon is at its furthest distance from Earth in its orbit (its apogee), during which its gravitational pull is reduced, resulting in a smaller than is usual, i.e. lower  and higher. Contrast.

apparent place: The apparent position of an object in space as seen by an observer, which, because of physical and geometric effects, may differ from the object's true position.

applied geography: The application of geographical knowledge and techniques to the solution of economic and social problems on any scale, ranging from to, in disciplines such as civic planning, and management, location policy, and population studies, among many others.

apposed glacier: A resulting from the merging of two separate glaciers.

apron: A spread of deposited by streams, especially those originating from a melting. See also ' and '.

aquiclude: A normally rock, underlying or overlying an, which becomes impermeable because of the saturation of its pores by water, potentially creating a.

aquifer:

An underground layer of rock, rock fractures, or unconsolidated materials such as gravel, sand, or silt, which is sufficiently porous to carry or conduct water yet also sufficiently coarse or non-absorptive to release the water and thereby permit its exposure to or access from the ground surface. Groundwater from aquifers may naturally emerge at the surface, e.g. at a, or may be extracted using man-made. There are many different types of aquifer with various levels of.

aquifuge: An rock stratum which not only obstructs the passage of water but cannot absorb it, e.g. granite.

aquitard: A or layer of rock that slows the conveyance of water from an due to its low  or low.

archipelago: A collection of in a sea.

arête: A sharp, narrow mountain, often resulting from the erosive activity of alpine flowing in adjacent.

arroyo:

A deep cut by a stream that flows only part of the year; a dry. The term is used primarily in areas in North America and South America.

Arctic: The region of the Earth that is north of the.

Arctic Circle: The northernmost of the Earth's two of, north of which the sun appears above the for 24 continuous hours at least once per year (and is therefore visible at midnight) and also appears at least partially below the horizon for 24 continuous hours at least once per year (and is therefore not fully visible at noon). Its latitude is approximately 66°33′47.1″ north of the. Contrast.

ash: Fragments of or rock less than 1/3 cm in diameter that have been ejected into the atmosphere by a explosion.

aspect:

The direction toward which a faces with respect to a or to the Sun's position in the sky, or the direction which a segment of  faces as it meets the.

Atlantic Seaboard fall line: The physiographic border between the Piedmont and Atlantic coastal plain regions of eastern North America. The name derives from the river rapids and that occur as the water flows from the hard rocks of the higher onto the softer rocks of the.

Atlantic-type coastline: See.

atlas: A bound collection of.

atmosphere: The mixture of gases, aerosols, solid particles, and water vapor that envelops the Earth.

atoll: A ring-shaped that partially or completely encircles a.

autonomous height: See.

aven: A vertical or inclined shaft connecting a passage to the surface.

avulsion: The sudden loss of land by the action of water. The rapid abandonment by a or of an existing  in favor of the formation of a new channel, typically because the new channel follows a steeper or less obstructed course.

awareness space: All of the locations of which an individual is "aware", i.e. about which they have knowledge above some minimum level, even those they may not have actually visited. Awareness space includes, and it enlarges as new locations are discovered and new information is gathered. See also ' and '.

axis: (coordinate system) Any of the reference lines of a Cartesian coordinate system, from which the signed distances to each coordinate are measured, e.g. the x-axis or the y-axis. (of a ) The imaginary central line or plane dividing the limbs of the fold as symmetrically as possible; the crest from which dip downward and away in an, or the lowest depth of the trough from which strata rise in opposite directions in a. (of the Earth) The rotational axis of the Earth: the diameter between the and the, passing through the planet's geometric center, around which the Earth rotates anti-clockwise (i.e. to the east) once every 23 hours and 56 minutes. This axis is constantly tilted at an angle of about 66°30' with respect to the plane of the Earth's orbit around the Sun, which is the primary cause of the seasonal weather cycles experienced at temperate and polar latitudes.

ayre: Another name for a or other gravel-covered,, or , used primarily in the of northern Scotland.

azimuth: The angle formed between a reference vector (often ) and a line from the observer to a point of interest projected perpendicularly to the on the same plane as the reference vector. Azimuth is usually measured in and can be determined with a.

azimuthal projection: A in which all are laid off correctly from the centerpoint of the map, so that all points on the map are true in distance and direction from the center.

B
backcountry: Any geographical area that is remote, isolated, undeveloped, or difficult to access, as contrasted with ; sparsely populated or uninhabited. See also.

backshore: The part of a lying inland from the, of the, from which it is often delineated by the presence of a. This part of the is only affected by waves during exceptional  or severe storms.

backslope: The part of the profile of a that forms the steepest, typically linear portion of the slope, generally located in the middle and bounded by a convex above and a concave  below. The backslope may or may not include vertical or near-vertical.

backwash: The seaward return flow of a receding wave after it has broken on a or other surface. Contrast.

backwater: A part of a in which there is little or no current, especially a side channel, a sluggish, or a slowing and widening of the created by an obstruction to flow. A place regarded as remote, underdeveloped, or culturally backward relative to other places; a place or state of stagnation, in which little or no economic, social, or intellectual progress occurs. A secluded, peaceful place.

badia: In the Middle East, an arid area characterized by low or irregular precipitation and little or no vegetation.

badlands: An area of rugged or irregular resulting from extensive wind and water erosion of unconsolidated sedimentary rock.

bajada:

A series of adjacent coalescing in a at the foot of a.

Balkanization: The political fragmentation of a larger or into multiple smaller regions or states, often implying mutual hostility or lack of cooperation between such units, as has occurred frequently in the Balkan Peninsula of southeastern Europe.

bank: The land alongside a, particularly the sloping ground bordering and defining the of a flowing such as a  or. An elevation in the of a river, stream, or shallow, either fully or partially submerged, mid-channel or connected to the, and usually made of sand, mud, gravel, or other loose sediment. See also ' and '. Another name for a or hillside.

bankfull stage: The during which the of a river or stream is completely filled with water from  to bank, immediately preceding the, when the river overflows its banks and inundates the surrounding.

bar: An elevated area of unconsolidated sediment such as sand or gravel which has been deposited by the flow of a or other moving body of water. See also.

barrage: An built for seasonal floodwater storage and/or to create a for irrigation, as opposed to a, which instead serves the purpose of hydroelectric power generation, though the terms are sometimes used more or less interchangeably.

barrier island: A long, narrow or lying above the  level (thereby creating an ) and parallel to the mainland, from which it is separated by a. Barrier islands are analogous to very large sandbars deposited naturally by wave and tidal action, often in extensive chains along the coastline, but may also be created artificially by. Though their size and shape change frequently, particularly during storms, they are important natural which shelter areas of relatively calm waters where  and marine life flourish. See also ' and '.

barrier reef: A lying parallel to a and some distance from it, creating a sheltered  which the reef protects from the.

barrier ridge: Any steep, unnavigable or isolating one  from another.

barrio: In the Spanish-speaking world, a or community within a larger urban area, generally with informal boundaries, though in some places the term may refer to a formal of a.

barrow: See.

barysphere: The and considered together, i.e. all of the Earth's interior beneath the.

base level: The lowest level to which a can erode its. The ultimate base level of all streams is.

baseline: An accurately measured line of known length on the Earth's surface, used as a base or reference line in and other operations.

basin: Another name for a, particularly one that is approximately circular, level or nearly level at the bottom, and/or surrounded on all sides by land of uniform elevation.

batholith: A very large body of, usually granite, which has been exposed by erosion of the overlying rock.

bathymetry: The measurement of water depth, mainly of and but sometimes of deep. The study and depiction of the physical features or of the of a lake or ocean. In this sense bathymetry is considered the underwater equivalent of or.

bay: A body of water that is directly connected to but recessed from a larger body of water, such as an,, , or another bay. The land surrounding a bay usually shelters it from strong winds and waves, making bays ideal places for and.

bayou: In the southern United States, a sluggish or stagnant or, or a outlet of a  or.

beach: A landform along the of an,, , or with a loose surface of sand, gravel, shingle, pebbles, shells, stones, or coral.

bearing: The direction or position of an object, or the direction of an object's movement, relative to a fixed point. It is typically measured in and can be determined with a. By convention, is defined as having a bearing of zero degrees.

bedrock: The solid rock in the Earth's that underlies all soil and other loose material; the rock material that breaks down eventually to form soil.

belt:

A large or (often but not necessarily a broad, elongated area of vague or indeterminate boundaries) identified or associated with one or more particular, distinctive characteristics, e.g. of climate (banana belt), vegetation (Pine Belt), topography (Alpide belt), geology or mineral resources (Lead Belt), agriculture (Corn Belt), land use, language or ethnicity (Hindi Belt), or social/cultural demographics (Bible Belt). See also.

bench: A narrow step, shelf, ledge, or, typically backed by a steep slope, produced either naturally (e.g. by erosion, as with a ) or artificially (e.g. by mining).

benchmark: A mark cut or embedded into a durable, fixed material, such as a rock or the wall of a building, for which the height above some designated has been accurately measured.

berg: A or hill; a face or precipice. Another name for a,, or.

bergschrund:

A or series of parallel crevasses that opens in a when a mass of moving ice detaches and pulls away from stagnant ice or. Bergschrunds are common in mountainous areas, often forming seasonally near the back of a where the ice meets a steep or rocky. When the rift forms directly between ice and rock, the gap is called a.

berm: A level space, shelf, or raised barrier separating two areas, often man-made and built of compacted earth. Berms often function as, fortification lines, or walls and other lines of demarcation. A low, impermanent, nearly horizontal or landward-sloping shelf,, or narrow on the of a  and parallel to the, formed by waves which deposit material beyond the average , e.g. during storms. Some beaches have no berms; others may have one or more.

bight: A bend or curve in a coastline, river, or other geographical feature typically indicating an especially large, open that is shallower than a.

billabong: In Australia, a branch of a river that is when the main stem changes course, leaving an elongated and often ephemeral or.

biological diversity:

A concept recognizing the variety of life forms in an area of the Earth and the ecological interdependence of these life forms.

biogeography: The study of the distribution of biological species and ecosystems in geographic space and through geological time.

biogeosphere: The outer part of the, from the surface of the Earth to the greatest depth at which organic life can exist.

biosphere: The entirety of all biological systems on Earth, integrating all living beings and ecosystems; the realm in which biological organisms live.

biota: The animal and plant life of a region considered as a total ecological entity.

blackwater: The water of a slow-moving river flowing through a forested or, characterized by high concentrations of tannins leached from decaying vegetation, which gives it a darkly stained color and high acidity.

blowhole:

A hole or, especially a nearly vertical one, that is the landward opening of a, frequently spouting or spraying air and as waves crash against the cave's other opening.

blowout: A sandy formed when wind erodes into patches of bare sand on otherwise vegetation-stabilized at the margins of coastal and arid ecosystems.

bluff: A steep slope or marking the outer margin of a, especially one formed as the river erodes the concave bend of a. See also.

bocage: A landscape of mixed woodland and, with fields and winding country lanes sunken between low, narrow ridges and banks surmounted by tall, thick, especially as found in rural parts of western Europe.

body of water: Any significant accumulation of water, either natural or artificial, on the surface of the Earth. Bodies of water may hold or contain water, as with and, or they may collect and move water from one place to another, as with, , and other.

bog:

A type of which accumulates deposits of dead plant material, especially mosses, known as peat. Bogs occur where the water at the ground surface is acidic and low in dissolved nutrients. They are one of four main types of wetland.

bootheel: See.

border: The geographical boundary of a political entity or legal jurisdiction, such as a,, or other subnational entity.

bore: (tidal) A steep-fronted wave formed by the convergence of two or by the constriction of an incoming tide as it travels up a,, or narrow , temporarily reversing the direction of the current. (hole) A deep, man-made hole or shaft drilled into the ground, e.g. in mining, or for digging a or tunnel.

bornhardt: A bald, steep-sided, dome-shaped hill, mountain, or rock at least 30 m in height and several hundred meters in width. Compare ', ', and.

borough: A type of in certain English-speaking parts of the world. Though traditionally used to refer to a fortress or a walled, modern usage of the term can variably refer to any town with its own local self-government, a formal or informal subdivision of a large (as in New York City and London), or an entire administrative  (as in the U.S. state of Alaska).

bottomland: See.

boulevardization: The replacement of the narrow, congested, winding streets of an older town or neighborhood with wider, more modern streets or boulevards, often according to a carefully plotted grid layout.

boundary: Any line of demarcation, real or imaginary, visible or invisible, natural or artificial, with or without legal significance, which may be perceived from either or both sides of the line, indicating the place at which two or more geographical areas of distinct ownership, administration, legal jurisdiction, or any other quality meet; e.g. a separating political or, zones of occupation, natural areas, or private and public property. See also.

bourne:

A seasonal or flowing from a in an otherwise dry, and whose flow depends on the level of the ; or the spring or fount itself. The term is used primarily in the of southern England. See also.

box canyon: A short, narrow with steep walls on three sides, allowing entry and exit only through the of the canyon.

brake: See.

brash ice: See.

breadbasket: A region of a country or other polity which supports a large proportion of the country's domestic food production (especially of wheat and other grains) due to its fertile soils, favorable climate, and/or relative accessibility to agricultural interests.

break: Any more or less abrupt change in the profile of a or hillside. A heavily eroded area along a featuring steep,, , or. The term is used chiefly in the plural (i.e. breaks) and primarily in the United States and Canada.

breaker: Another name for a. A,, , , or area of shallow water against which waves routinely break.

breaker zone: See.

break-in-bulk point: A transfer point on a transport route where the mode of transport or type of carrier changes and where large-volume shipments are reduced in size. For example, goods may be unloaded from a ship and transferred to trucks at an ocean port.

breaking wave:

A wave of water on the surface of an,, or other with enough energy that, upon reaching a peak size or velocity, its crest "breaks" or overturns upon itself with a distinct forward curve, with the linear energy transforming into turbulence. Waves tend to break as they enter areas of shallow water, most reliably near, where the decreasing depth of the sea floor beneath them forces them to grow to a critical height at which point they overturn and the remaining forward energy is dissipated upon the as , though other forces may also cause breaking, including stormy weather and passing watercraft.

breakwater: Any man-made structure built on the of a body of water, typically the, in order to reduce the intensity of wave action in an area adjacent to the shore, thereby providing safe harbourage for human activities in the inshore waters. Breakwaters may also be designed to protect the coastline from coastal erosion and.

brownfield land: Any previously developed area of land that is no longer in use, often with derelict buildings and infrastructure, in some contexts implying land that has been abandoned because of pollution or contamination.

brush: Low-lying, woody, often dense vegetation or plant debris, e.g. ; a thicket of small trees and shrubs, or the plant community characterized by vegetation dominated by shrubs.

built environment: The human-made spaces that provide the setting for human activity, in which people live, work, and recreate on a day-to-day basis.

burgh: A type of in Scotland and northern England, equivalent to a.

burn: In parts of the United Kingdom, Australia, and New Zealand, a large or a small. See also.

bush: Wild, undeveloped, or uncultivated land, especially when covered by thick shrubs and vegetation; sparsely populated or uninhabited. See also ', ', ', and '.

bushveld:

In southern Africa, a tropical or subtropical woodland consisting largely of open with scattered trees; wild countryside as opposed to cultivated land.

butte: An isolated or with steep or precipitous sides, usually having a smaller summit area than a.

bypass: A which diverges around a place rather than traveling through it, especially a road or footpath built specifically for the purpose of diverting automobile or pedestrian traffic away from areas that are congested, blocked, under construction, or unsafe. See.

C
cadastre:

A type of parcel-based land recording system containing a comprehensive record of interests in individual units of land within a or other polity, usually including a geometric description of each parcel's physical location, dimensions, and that is linked to legal information detailing the nature of the interests (e.g. rights, restrictions, and responsibilities), the ownership or control of those interests, and the economic value of the land and its improvements. The cadastre is a fundamental source of data used in resolving disputes between landowners.

cairn: A man-made stack or of rocks, stones, or masonry, usually roughly conical or pyramidal in shape, constructed as a burial mound, to mark a point, or as a  or  to aid  on a  that is otherwise unmarked and difficult to distinguish from the surrounding environment.

calanque: A narrow, steep-sided surrounding an formed in  regions along the Mediterranean coast, either by  erosion or the collapse of the roof of a  that has been subsequently partially submerged by a rise in.

caldera: A very large cauldron-shaped of volcanic origin which forms through the subsidence and collapse of the ground surface following the evacuation of an underlying magma chamber. See also.

campo: In the Spanish-speaking world, the rural countryside or the. In Brazil, an area of level, open with scattered trees, comparable to a.

canal: A navigable artificial water, usually built as a conduit for human activity.

canebrake:

A dense thicket of giant cane grasses, often lining a or other body of water. The term is used primarily in the southeastern United States.

canyon:

A deep cleft between or, or a rift between two mountain peaks, resulting from and the erosive activity of a  over long periods of geologic time.

cape: A large or extending into a body of water, usually a  or.

capillary fringe: The soil layer lying immediately above the, in which water is drawn up and held within pore spaces by capillarity.

capital: A primary or of a country, state, province, or other subnational polity, especially one that is a seat of government for the entire polity, either by law or by virtue of being the physical location of the government's offices and meeting places, or both. A capital is often but not always the largest or most economically or historically important city of its constituent. A polity may have one or more capitals, or none. Any place considered to have informal primacy or importance with respect to some characteristic or association, e.g. Milan, Italy is sometimes unofficially called the "Fashion Capital of the World".

caprock: A stratum of erosion-resistant (usually limestone) found in arid areas. Caprock forms the top layer of most and.

cardinal directions: The set of four primary directions used in and : north (N), south (S), east (E), and west (W). Together they form the primary divisions of the. They can be further subdivided into the and.

carrying capacity: The total number of human beings that an area can support given the quality of the natural environment and the level of technology of the population.

cartography: The study and practice of making and. A person who draws or makes maps or charts is called a cartographer.

cartogram: A map in which some thematic mapping variable, such as travel time, population, or gross national product, is substituted for traditional measures of land area or distance such that the geometry or space of the map is distorted in order to convey and emphasize the information of the alternate variable.

cartouche: A decorative panel or emblem on a or a, enclosing the title,, , or any other information.

castle koppie: See.

cataract: A large, or a long series of in a river, of the type occurring in the river Nile.

catchment: See.

causeway: A track, road, or railway raised above a body of water or a low-lying place by virtue of being built upon a man-made embankment, typically constructed of earth, masonry, wood, or concrete. Compare.

cave: Any naturally hollow underground space large enough for a person to enter.

cavern: A type of solutional that is formed in soluble rock with the ability to grow speleothems.

cay:

A small, sandy, low-elevation on the surface of an otherwise submerged ; a type of coral island. Compare.

celestial pole: Either of the two imaginary points in the sky at which an indefinitely extended projection of the Earth's axis of rotation intersects the celestial sphere. As the Earth rotates upon its axis, the north and south celestial poles remain permanently fixed in the sky (directly overhead to observers at the and, respectively), and all other points appear to rotate around them.

cenote: A natural pit or resulting from the collapse of limestone which exposes  underneath.

census-designated place (CDP): A concentration of population identified by the United States Census Bureau for statistical purposes.

central business district: A centrally located commercial business in an area, typically containing a concentration of office and retail activities.

centroid: The point in a geometric figure for which the coordinates are the average values of the coordinates of all other points in the figure, i.e. the arithmetic mean position of all points in the figure; or the point with the smallest possible average distance from all other points of the figure. In geography, the of a region of the Earth's surface is the centroid of the two-dimensional shape of that region, as projected radially to or onto a.

chain: A unit of length equal to 66 ft, used especially in public land in the United States; 10 square chains is equal to 1 acre. Though the literal chains used to measure this distance have long been superseded, surveying tapes are often still called "chains", and measuring with a tape may be called "chaining".

channel:

A separating two relatively close landmasses. Any narrow that connects two larger bodies of water. The deepest part of a shallow body of water, often used as a passageway for large ships.

chaparral: A class of terrestrial vegetation characterized by dense, impenetrable thickets of thorny shrubs or dwarf broadleaved trees, commonly found in northern Mexico and the southwestern United States.

chart: A special-purpose designed for, especially nautical and aeronautical navigation, or to present specific data or technical information.

chimney: See.

chine: A steep-sided, typically of soft eroding of sandstone or clay, through which a river or stream flows to the sea. The term is used primarily in southern England.

chinook: A warm, dry wind experienced along the eastern side of the Rocky Mountains in the United States and Canada. Most common in winter and spring, it can result in a rise in temperature of 20 C-change in a quarter of an hour.

chorography: The art of establishing, describing, or mapping a geographic or, or more broadly, the representation of space or place.

chorology: The study of the causal relations of the phenomena present in a region; a comprehensive explanatory study of a region.

choropleth: A showing the distribution of a phenomenon by graded shading which indicates the density per unit area of that phenomenon; the darker the shading, the greater the density.

chott:

An ephemeral, often highly that forms seasonally with fluctuations in the, usually in the winter, in the basins of Northwest Africa.

cinder cone: A steep-sided formed by the explosive eruption of cinders that form around a. Cinders are fragments about 1 cm in diameter.

circle of latitude: See.

cirque:

An amphitheatre-shaped surrounded on three or more sides by steep, -like slopes and formed by glacial or fluvial erosion.

city: A large human, generally with extensive systems constructed for housing, transportation, sanitation, utilities, and communication.

city center:

city-state: A sovereign or small independent that usually consists of a single  and its dependent territories.

clearing: The practice of permanently removing vegetation, especially trees and bushes, from a or woodland in order to use the space for another purpose, such as agriculture, civic development, or paths for roads, railways, or power lines. Another name for a.

cliff: Any vertical or nearly vertical rock exposure, usually formed by the processes of and.

cliffed coast:

A where the repeated action of ocean waves has formed steep and often precipitous, as opposed to a flat or gently sloping.

climax vegetation: The vegetation that would exist in an area if growth had proceeded undisturbed for an extended period. This would be the "final" collection of plant types that presumably would remain forever, or until the stable conditions were somehow disturbed.

clinometer: See.

coast:

The area where land meets a or. Coastal zones are regions where interactions between terrestrial and marine processes occur. Compare.

coastal bench: See.

col:

The lowest point on a between two peaks.

colatitude: The complementary angle of a given ; i.e. the arithmetic difference between 90 degrees and the given latitude. For example, the colatitude of is.

colony: A under the immediate complete political control of a sovereign but otherwise distinct, often geographically, from the state's home territory. Colonies have no international representation independent of the metropolitan state. Compare.

colluvium: Loose, unconsolidated sediment that has been transported and at the base of a by any of various wash or  processes, such as,, or. Typically a heterogeneous mixture of rock types and sizes ranging from silt to boulders, colluvium is often derived from, and differs from , which is deposited primarily by  activity.

combe:

A steep, narrow or a large hollow on the side of a or, especially one enclosed on all but one side. The term is used primarily in southern England, where it often implies a dry in a limestone or chalk. See also.

commonwealth:

compass: An instrument used for and orientation that indicates direction relative to the geographic by measuring the orientation of the Earth's magnetic field with respect to the. Compasses often display markings for angles or, which allow them to show and, in addition to a.

compass rose:

A figure on a,, nautical chart, or monument used to display the orientation of the four — North, East, South, and West — and their intermediate points.

compass survey: A which relies on the indications of a magnetic for orienting the traverse as a whole or for determining the directions of individual lines.

confluence: The place at which two or more or other flow together to form one larger river or watercourse.

coniferous: Bearing cones; from the conifer family.

contiguity: The characteristic of a group of neighboring political or geographical divisions not being interrupted by politically unaffiliated land or water. Such divisions are said to be contiguous.

continent: One of several very large, contiguous into which the Earth's land area is divided, generally by geographical or political convention rather than any strict criteria. Geologically, continents correspond largely to areas of continental crust on.

continental climate: The type of climate found in the interior of the major continents in the middle or latitudes. The climate is characterized by a great seasonal variation in temperatures, four distinct seasons, and a relatively small annual precipitation.

continental divide: The line of high ground that separates the different oceanic of a particular. The river systems of a continent on opposite sides of a continental divide flow toward different oceans. See.

continental shelf: A portion of a that is submerged beneath an area of relatively shallow water known as a shelf sea. Though continental shelves are usually treated as physiographic provinces of the, they are not part of the deep ocean basin proper but the flooded margins of the continent.

continentality: The quality of being located on a.

contour line:

A line marked on a which connects points of equal above or below a specified reference. Multiple contour lines, each representing a different elevation, are depicted together to show the of the  within the map area.

contour interval: The difference in between any two adjacent as depicted on a particular topographic map.

conurbation: An extensive urban area formed when two or more initially separate coalesce to form a continuous.

cordillera: A long chain of or, especially those formed by the same orogeny and spanning the length of a along  boundaries. The term is used in particular to refer to the American Cordillera, an almost continuous system of parallel ranges lining the west coasts of North, Central, and South America.

core area: The portion of a country or territory that contains its economic, political, intellectual, and cultural focus. It is often the center of creativity and change. See also.

cornice: An accumulation of ice and wind-blown snow overhanging the edge of a ridge or cliff face, usually on the side of a steep mountain.

corrasion: The process of mechanical of the Earth's surface by the impact or grinding action of particles being transported across it, either by moving water, waves, glaciers, wind, or gravity.

corrie loch: See.

cosmopolitan: Occurring worldwide; belonging to all parts of the world and free of geographical or political limitations. See also.

coulee: A dry eroded by Pleistocene floods that cut into the lava beds of the Columbia Plateau in the western United States.

couloir: A narrow with a steep gradient in a mountainous terrain, often enclosed by sheer and filled with snow or ice even during the summer months.

country: A identified as a distinct national entity in. Compare.

county: A type of subnational division of a or used for administrative or other purposes.

course: The in which a vessel or aircraft is moving, or in which it is steered. This is not necessarily the same as the, the direction in which the craft's bow or nose is pointed; any difference between heading and course is due to the motion of the air or water through which the vessel is moving, or other aerodynamic effects such as skidding or slipping. See also.

cove: A walled, rounded, -like opening at the head of a small. A small, narrow, sheltered,, , or recess in an , often within a larger embayment. A small, often approximately circular, wave-cut indentation or recess in a on a large body of water, especially one with a relatively narrow or secluded entrance. A shallow tidal river, or the near the of a tidal river.

crater: Any large, roughly circular, pit, or hole in the Earth's surface. Craters are classified into different types based on their ultimate causes; see ', ', and.

crater lake: A that forms in a or  (such as a ), an  left by a meteorite, or a crater resulting from a man-made explosion.

craton: An old and stable region of, characterized by a thick composed of ancient crystalline basement rock. Cratons are generally found in the interiors of, having remained relatively unaffected by orogenic and tectonic activity for very long periods of time.

creek: A small, intermittent that is larger than a but smaller than a. The term is used primarily in the United States, Canada, and Australia.

crevasse: A deep crack,, or chasm in the ice of a or, or more generally in any ground surface. A break in the natural or of a river.

crust: The thin shell of solid material that is the Earth's outermost layer and the outermost component of the. The Earth's crust is generally divided into two distinct types, and, both of which "float" on top of the.

cryosphere: The totality of water in the solid phase on the Earth's surface, including ; sea, lake, and river ice; snow; and permafrost. The cryosphere is sometimes considered a subset of the.

cryoturbation:

The mixing of materials from various horizons of the soil down to the due to freezing and thawing.

cuesta: A long, low with a steep scarp slope and a gentle (dip slope).

cultural geography: A branch of which studies the patterns and interactions of human in relation to the natural environment and the human organization of space.

culture: The accumulated habits, attitudes, and beliefs of a group of people that define for them their general behavior and way of life; the total set of learned activities of a people.

culture hearth: The area from which the of a group diffused. See also.

culvert: A tunnel or conduit that channels water through or beneath an obstacle (e.g. through a man-made crossing of a that would otherwise block the natural flow of water), or any artificially buried.

curvimeter: See.

cusp: An arc-shaped, -like mound of sediment on a or. Cusps tend to be uniformly spaced in repeating patterns close to the shoreline, with the embayment of each arc made of fine-grained sand or gravel and the "horns" made of coarser sediment.

cut bank: A continually along a meandering  or, especially a bank that has been eroded into a nearly vertical. Cut banks generally form on the outside bend of a deep, opposite the depositional that forms on the inside bend.

cutoff: The new channel formed when a erodes through a narrow strip of land and thereby shortens the length of the main channel.

cwm: See.

Cyclopean stairs: A term referring to the longitudinal profile of some which have been eroded into a series of consecutive  resembling stairs.

D
dale: Another name for a.

dam:

Any barrier, either natural or artificial, that stops or restricts the flow of water, either on the surface or underground. Man-made dams are most commonly built to impound rivers or streams, generally to retain water for purposes such as human consumption, irrigation, aquaculture, or power generation (whereas related structures such as floodgates and are more specifically designed to manage or prevent water flow into particular areas).

dasymetric map: A type of thematic that uses areal symbols to visualize a (e.g. population density) by refining a  with ancillary information about the distribution of the variable. The dasymetric method attempts to improve the resolution of maps based on average or per-capita figures calculated for discrete administrative units, which tend to show sharp contrasts between adjacent areas, by supplementing these figures with additional geographic data that allow more precise categories to be constructed. Dasymetric maps are a hybrid of choropleth and, combining their strengths and weaknesses in order to more accurately depict quantities that vary continuously across space.

datum plane:

The zero-elevation baseline or to which a measurement of or  is relative, e.g. the  calculated for a given location over a given period of time. See also.

de facto segregation: The spatial and social separation of populations that occurs without legal sanction.

de jure segregation: The spatial and social separation of populations that occurs because of legal measures.

debouch:

A place where water runoff from a relatively small, confined space emerges into a much larger, broader space, or where a pours forth from a narrow opening, such as where a stream or river enters a lake or ocean.

deciduous forest: A forest composed of trees which lose their leaves each year.

deep: A trough-like or trench in the, of limited extent but great depth, generally more than 5500 m below sea level.

deferred junction:

defile: A narrow or between  or.

degree: A unit of angular measure, represented by the º symbol. A circle is divided into 360 degrees; subdivisions of the degree include the ($1/undefined$ of one degree) and the ($1/undefined$ of one degree). Degrees are commonly used to divide the roughly spherical shape of the Earth for geographic and cartographic purposes, e.g. when reporting and.

degree day: Deviation of one-degree temperature for one day from an arbitrary standard, usually the long-term average temperature for a place.

dell: A small, secluded hollow, usually within a grassy, park-like, partially wooded.

delta: A landform at the of a where the  splits up into several. It is formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Compare.

demilitarized zone (DMZ):

demography: The study and systematic analysis of, particularly human population.

demoiselle: A pillar of rock weathered from volcanic breccia or similar material and capped by a large boulder which has protected the material underneath.

demonym:

A word identifying a person or a group of people in relation to a particular place, usually derived from the name of the place (which may be any kind of place, formal or informal, of any size or scale, from a town or city to a region, province, country, or continent) and used to describe all residents or natives of that place, regardless of any ethnic, linguistic, religious, or cultural differences which may exist within the local population. Examples include "Vietnamese", describing a person from Vietnam; "Detroiter" for a person from the city of Detroit, Michigan; and "Macedonian" for a person from North Macedonia or the wider historical region of Macedonia.

denudation: The uncovering of deeper layers of rock by any natural process, e.g.,, or.

dependency:

A relying on or subject to the control of another, neither possessing full political independence nor forming an integral part of the controlling country's political or economic interests.

deposition: Any natural process by which material such as soil and rocks is added to a or, e.g. by the action of wind, water, ice, or gravity in transporting previously surface material, which comes to rest when sufficient kinetic energy is lost and accumulates in layers of sediment. See also.

depression: Any that is sunken or depressed below the surrounding area. Depressions include an enormous variety of landforms and can form by a number of different mechanisms, including,, , , and.

derelict land: An area of land which has been damaged or devalued by some process, either natural or man-made (e.g. extractive industry), and/or simply neglected, causing it to be abandoned by human interests (and often other organisms) and leaving it incapable of being used productively in its present condition. See also.

desert: An arid, barren area of land where little precipitation occurs and living conditions are consequently unfavorable for most plant and animal life. Deserts are characterized by exposure of the unprotected ground surface to processes of as well as large variations in temperature between night and day. They are often classified by the amount of precipitation they receive, by their average temperature, by the causes of their, or by their geographical location.

desert pavement:

A ground surface, often found in arid environments, covered with interlocking rock fragments of pebble and cobble size, closely packed after the removal of finer rock material and smoothed or polished by blown sand so that eventually their upper surfaces are more or less uniformly flat.

desert varnish:

A conspicuous orange-yellow to black coating often present on exposed rock surfaces in arid environments, consisting of thin, hard, polished layers of metal oxides, especially iron and manganese, which form when minute quantities of matter migrate to the surface of the rock by capillary action and are then precipitated by evaporation.

desertification: The process by which a previously fertile area becomes increasingly arid, infertile, or -like; a type of land degradation in which biological productivity is lost due either to natural or man-made processes, e.g. climate change or overexploitation of soils for agriculture.

desire line: A straight line drawn on a between the point of origin and the destination of a trip, i.e. the shortest distance between these two points, indicating the route a person would like or desire to follow if it were possible.

desire path:

Any path or trail, often a footpath, created as a consequence of erosion caused by repeated human or animal traffic, usually because it is the shortest or easiest to navigate between an origin and a destination. Desire paths often emerge as shortcuts where constructed paths or roads are circuitous, have gaps, or are non-existent.

dew pond: A shallow artificial built to capture and hold rainwater or sea mist in order to provide water for livestock, made especially in areas where natural supplies of surface water are not readily available, such as on the chalk downlands of southern England.

diapir: A type of in which a more mobile, ductile, or deformable rock or other material is forced to intrude into relatively brittle overlying rocks.

diaspora: The scattered dispersion of a human population from its original homeland; or the members of a dispersed population, now residing in various locations to which they are not indigenous.

digital elevation model (DEM): A three-dimensional computer graphics representation of a geographic surface created from data. DEMs are the most common basis for digitally produced relief maps.

dike: A ditch, wall, embankment, or ridge, natural or man-made, that is an obstacle to something else; another name for a. In, an intrusion in which molten rock has ascended through an approximately vertical and solidified into a wall of rock that is often harder or less permeable than the rocks of the surrounding strata.

diocese: A type of administrative division used by certain Christian churches for religious purposes.

direction: The of one point relative to another without reference to the distance between them, usually expressed as the angular distance in between a line connecting the two points and a reference direction. In,, and , direction is often considered only with respect to a two-dimensional plane (see ), but it is also commonly interpreted in three dimensions.

discharge: In, the volumetric flow rate of water through a particular cross-sectional area, i.e. the volume of water that passes a particular point along a waterway (e.g. a cross-section of a ) per unit time. The measure includes the volumes of any suspended solids, dissolved chemicals, or organic matter in addition to the water itself. Discharge is commonly measured for both natural and man-made hydrological systems, where it may be referred to by various names including streamflow and outflow.

discordant coastline:

A which cuts transversely across the predominant orientation of the local geological strata, i.e. not parallel to them, as with a.

dissected plateau: A landscape produced by significant erosion and incision of a such that only a small part of the plateau surface is at or near the original elevation of the summit; much of the area instead occurs as eroded  or.

distance decay: The decrease in cultural or spatial interactions between two places as the distance between them increases. This effect may be noticeable in and, where certain characteristics such as pedestrian traffic, building height, and land value tend to decline with greater distance from the.

distributary: A or that branches off and flows away from a  and does not return to it. Distributaries are common near. Contrast.

district: A type of used by governments and institutions worldwide, typically at regional or local levels. Districts are commonly drawn to define the jurisdictions of special local government services, such as law enforcement and education, and often function more or less independently of the or  governments that designate them. The term can refer to a wide variety of official and colloquial subdivisions, including electoral districts, school districts, and shopping districts.

divide: See.

doab: In parts of South Asia, the low lying between and reaching to the of two rivers or streams. See also.

doline:

A shallow enclosed or funnel-shaped typical of  landscapes, usually with a flat floor and linked to the underlying drainage system by a vertical shaft. See also.

dome: A steep-sided that forms when very viscous lava is extruded from a. An uplifted area of sedimentary rock with a downward dip in all directions, often caused by molten rock material pushing upward from below. The sediments have often eroded away, exposing the rocks that resulted when the molten material cooled.

donga: In southern Africa, another name for a or carved by extreme erosion.

dormant volcano: An active that is in repose (quiescence) but is expected to erupt in the future.

dormitory town: See.

downland:

An open, treeless expanse of gently undulating, elevated, usually of chalk and supporting grazing for livestock. The term is used primarily in southern England, Australia, and New Zealand.

downtown: In English-speaking North America, the commercial, cultural, and often historical and/or geographical of a or, especially a large city within a major, often synonymous with its.

drainage: The natural or artificial removal of surface and/or sub-surface water from an area with excess water, e.g. via facilitated by such as  and, into which water collects and is transported to  by gravity. The patterns, hierarchies, and evolution of drainage networks are widely studied in disciplines.

drainage basin:

Any area of land where precipitation collects and drains into a common outlet, such as into a,, , or any other. The drainage system includes all of the from precipitation and snowmelt, as well as all of the  beneath the Earth's surface. Each drainage basin is separated topographically from adjacent basins by a.

drainage divide:

The topographical barrier that separates neighboring. Divides are often, though not always, located along conspicuous elevated or.

draw:

A terrain feature formed by two parallel or with low ground in between them. Another name for an,, or , especially one with a broad floor and gently sloping sides.

draw down: The maximum extent to which the is reduced in as a result of pumping water from a  that penetrates an. The amount of draw down diminishes logarithmically with distance from the site of the well, a fact which determines the shape of the subsurface in the area surrounding the well.

drift: All sediment transported by a, sorted or, whether deposited directly by the ice or by glacial.

drift ice:

A type of consisting of multiple that are not attached to the  or any other fixed object such as a, and which are therefore free to "drift" under the influence of winds and. Contrast.

drowned valley: A which was originally formed on land but later partially or entirely submerged beneath the sea due to a rise in sea level. See also ', ', and.

drumlin: An elongated in the shape of an inverted spoon or half-buried egg which is formed by ice acting on underlying unconsolidated  or ground.

dry farming: A type of farming practiced in semi-arid or dry grassland areas without irrigation, instead using such approaches as fallowing, maintaining a finely broken surface, and growing drought-tolerant crops.

dry gap: See.

dry point: An area of firm or dry ground in a,, or , often capable of supporting a human.

dryland: An or more generally any land area defined by a relative scarcity of water, where precipitation is evenly balanced or exceeded by evaporation from surfaces and evapotranspiration by plants. Drylands encompass all sub-humid and arid environments, from tropical to hyper-arid extremes such as.

dune: A hill of loose sand built by the movements and erosional and processes of wind or water, often occurring in and  areas.

E
Earth science:

A collective term for the various fields of natural science related to the planet Earth. The branch of science that studies the physical constitution and characteristics of the Earth and its atmosphere, using methods and tools from, geology, physics, chemistry, biology, and mathematics to build a quantitative understanding of how the Earth works and changes over time.

earthquake: A sudden and intense shaking of the ground due to activity.

Eastern Hemisphere: The of the Earth that is east of the and west of the. It is opposite the.

easting:

economic distance: The physical distance a commodity may travel before its value is exceeded by the costs of transporting it.

economic geography: A sub-discipline of geography which studies the location, distribution, and spatial organization of economic activities across the world.

economies of agglomeration: The economic advantages that accrue to an activity by locating close to other activities; benefits that follow from complementarity or shared public services.

econym: See.

ecoregion:

A type of province that is smaller than a and which contains characteristic, ecologically and geographically distinct, and relatively uniform assemblages of biological communities and species. Ecoregion boundaries often overlap within and mosaic habitats, and most ecoregions contain habitats that differ from those described for their assigned biome.

ecotone: A transition area between two biological communities, where different communities meet and integrate. It may manifest as a gradual blending of the communities across a broad area, or as an abrupt boundary line.

ecumene:

The habitable world according to the ancient Greeks; the part of the Earth's surface that is suitable for permanent human settlement, e.g. because it is climatically tolerable and physically occupiable. All of human civilization considered collectively.

edge city: A concentration of businesses, commercial buildings, or retail and entertainment venues situated outside of a traditional or central business district in what was previously a residential or  area.

edgelands: The transitional areas of "fringe" space at the boundaries of a,, or other artificial geographical entity, often distinguished by a partly man-made, partly natural landscape that is in the earliest stages of human management and organization. Compare.

effective accessibility: The extent to which a place or service is actually accessible, governed not only by the distance to be traveled but also by whether or not the means of transport, the time available, and social circumstances make access possible.

ekistics: The scientific study of human of all types, incorporating concepts such as regional, metropolitan, and community planning and dwelling design with the goal of achieving harmony between the inhabitants of a settlement and their physical, social, and cultural environments.

electoral geography: A branch of concerned with analysis of the organization, methods, results, and consequences of political elections in the context of geographic space and using geographical techniques.

elevation: The height of a geographic location above or below a fixed reference point; in particular, the height of a point on the Earth's surface with respect to (or at least to a  used as an approximation of the Earth's mean sea level). Compare ', ', and. The vertical angle between the horizontal and a high point, e.g. between the and a star in the night sky, or between the base of a mountain and its. In architecture, a view of one of the sides of a building, or a drawing of this view.

ellipsoid: See.

emergence: The rise of the level of a land surface with respect to the sea, so that land formerly under the sea becomes dry. The location at which an or comes to the surface.

emergent coastline: A or resulting from a rise in land surface elevation relative to sea level.

empolder: To by the creation of a.

enclave: A tract or territory completely surrounded by and enclosed within the territory of exactly one other state, country, or other political entity. Unlike enclaves, can be surrounded by more than one other state.

endemic: Restricted or exclusive to a certain place,, or people, having originated there, and existing nowhere else.

endorheic basin:

A closed that allows little or no outflow to external bodies of water but converges instead into internal or  which equilibrate through evaporation.

englacial: Embedded within a. Contrast ' and '.

entrepôt:

A place (e.g. a, city, or trading post) to which physical goods or merchandise are brought to be stored temporarily while awaiting export to another country, and where they are not liable to customs duties. Though the term once described important commercial centers situated along long-distance trade routes, modern customs areas have largely made such entrepôts obsolete, and the term is now more commonly used to refer to duty-free ports with a high volume of re-export trade.

environs: The area surrounding a particular geographical place, i.e. its surroundings or environment.

epeiric sea: A large, shallow body of on a which is connected to the ; an. See also.

epicenter: The point on the Earth's surface directly above the of an, near which the seismic waves produced by the earthquake are usually most noticeable.

equal-area projection:

equator: An imaginary line dividing a spheroid such as a planet into northern and southern, defined by the intersection of the spheroid's surface and the plane perpendicular to its axis of rotation, which results in a exactly midway between and hence equidistant from the planet's and is therefore defined as zero degrees. The Earth's equator in particular (often capitalized as the Equator): the imaginary circle of latitude halfway between the geographic poles which is assigned a latitude of zero degrees (0°) and therefore used as a reference point from which all other are measured. At 40074 km in circumference, is the largest great circle of the Earth. Places located on or near the Equator experience approximately the same amount of daylight year-round, which causes local daytime temperatures and climate patterns to be relatively stable throughout the year.

equatorial cylindrical orthomorphic map projection: See.

equidistant:

equirectangular projection:

erg:

A broad, flat area covered by wind-swept sand and having little or no vegetative cover.

erratic: A boulder that has been carried from its source by a and deposited as the glacier melted. Such boulders are often conspicuous because they differ geologically from the surrounding rock.

escarpment: A long or steep slope separating two comparatively level or more gently sloping surfaces and resulting from erosion or faulting.

esker:

A long, winding ridge of stratified sand and gravel, usually occurring in or formerly glaciated areas.

estavelle:

A or  which, depending on the season and weather conditions, can serve as either a sink or a source of.

estuary: The broad lower course of a where it enters the ocean and is affected by the. Compare.

étang: A shallow pool or caused by the ponding of draining from a  by material brought ashore by the sea.

etchplain: A beneath which the has been subjected to considerable subsurface weathering, known as "etching". Erosion of the overlying an etchplain often exposes topographical irregularities such as.

evorsion: See.

exaration: See.

exclave: A portion of a state or territory that is geographically separated from the main part by surrounding foreign territory of one or more other states or political entities. Many exclaves are also.

exotic stream: A found in an area that is too dry to have spawned such a flow. The flow originates in some moister section.

extinct volcano: A that is not expected to erupt again.

exurban: An adjective describing a region or district that lies outside a and usually beyond its ; a place of this type is called an exurb. Compare.

F
fairway: The part of a containing the navigable, in particular the central, deepest, widest, or most commonly used channel.

fall line: A unconformity between an region of relatively hard crystalline basement rock and a  of softer sedimentary rock.

fallow: Agricultural land that is plowed or tilled but left unseeded during a. Fallowing is usually done to conserve moisture and soil nutrients.

false origin: A selected point in a from which the position of any place can be expressed in terms of its coordinates with respect to the selected point. The false origin differs from the in order to exclude negative values.

fast ice:

that is more or less securely "fastened" to a,, or to grounded , and which therefore does not move with currents and winds (unlike ). The formation of fast ice is usually seasonal and its properties vary with water depth, of the sea floor,, and pressure from adjacent drift ice.

fault: A fracture in the Earth's crust accompanied by a displacement of one side of the fracture.

fault-block mountain: A mountain mass created by either the uplift of land between or the subsidence of land outside the faults.

fault zone: An area of numerous in the Earth's crust along which movement has occurred. The movement may be in any direction and involve material on either or both sides of the fractures.

federation: A form of government in which powers and functions are divided between a central government and a number of political subdivisions that have a significant degree of political autonomy.

fell: A wild, barren, high-altitude or, or a treeless, often studded with boulders or rock outcrops; or a broad, isolated mountain. The term is used primarily in northern England, Scotland, and Fennoscandia.

felsenmeer: See.

fen: An area of spongy, waterlogged ground containing decaying vegetation that accumulates over time into peat, and which is supplied with an input of mineral-rich or and thereby directly connected to a larger hydrological system. This external input typically results in higher mineral concentrations and a more alkaline pH than other peat-forming ecosystems such as. Fens are one of four main types of, along with bogs,, and.

field: Any large, open, outdoor space, natural or man-made, especially one with a natural surface covering such as grass or soil and having few trees and structures, permitting long. (variable) A property, quantity, or observation (e.g. temperature, soil moisture, population density, etc.) that can be theoretically assigned to any point of space and which varies across space. Both scalar and vector fields are found in applications, although the former is more common. Also spatially dependent variable.

figure of the Earth: The size and shape of the Earth as studied in. Applications requiring varying levels of precision have led to the development of many different models of the Earth, ranging from simple spheres to much more accurate approximations such as.

firn: A type of ice that is at an intermediate stage between snow and ice. More specifically, firn is partially compacted left over from past seasons which has subsequently recrystallized into a form that is harder and denser than névé.

first bottom: A colloquial term loosely applied to the topographically lowest step of a that experiences regular flooding (though the frequency considered "regular" is inconsistently specified), i.e. the first part to be inundated when a flood occurs. The term is used primarily in the Midwestern United States.

First Law of Geography:

A fundamental assumption of articulated by the Swiss-American geographer Waldo Tobler as "Everything is related to everything else, but near things are more related than distant things." This principle is considered foundational to the concepts of and, and is expressed mathematically in the inverse distance weighting method of spatial  and in  as the basis for.

firth: Another name for a coastal,, or associated with the of a large , where the  effects of  passing upriver have widened the riverbed into an. The term is used primarily in Scotland.

fish ladder: A series of shallow steps down which water is allowed to flow, designed to permit salmon or other anadromous fish to circumvent artificial barriers such as as they swim upstream to spawn.

fissure: A long, narrow opening or line of breakage made by cracking or splitting, especially in rock or earth.

fjard: A large, open, between the  of an  or between an island and the, either on the sea coast or in freshwater lakes or rivers.

fjord:

A long, narrow, marine with steep sides or  created by  erosion.

flark: A or within a, often water-filled and usually occurring as part of a repeated series of such depressions which are elongated and parallel to each other and separated by intervening ridges known as strings.

flood bypass:

flood wall: A primarily vertical artificial barrier designed to temporarily contain the waters of a or other which may rise to high levels during flooding events. Flood walls are narrower and typically easier to build than or, so they are mainly used in locations where space is limited or where building more traditional flood-control structures would interfere with other interests.

floodbank: See.

floodplain:

A broad, flat area of land adjacent to a or which is leveled by annual flooding and by the lateral and downstream movement of.

floodway: Another name for a. A large-capacity or designed to capture and divert floodwaters or excess streamflow from populous or flood-prone areas and eventually drain it into a river or other body of water, e.g. an artificial drainage canal bounded by. They often run below street level in larger cities. A road crossing of a flood-prone channel, built at or close to the natural ground level. It is similar to a but crosses a shallow and often dry that is subject to flooding, rather than a continuously flooded waterway. A part of a kept clear of encumbrances and reserved for emergency diversion of floodwaters.

floor: The level or nearly level lower part of a or, or the of any, such as a , , or.

flute: A landform created by the movement of a glacier around a boulder, consisting of a lineation or streamlined furrow or parallel to the direction of ice movement. They generally form in newly deposited or older  and can reach heights of 25 m and lengths of 20 km.

fluvial: Of or pertaining to or ; produced by the action of a river or stream.

fluvial terrace:

focality: The characteristic of a place that follows from its interconnections with more than one other place. When interaction within a region comes together at a single place (i.e. when the movement focuses on that location), the place is said to possess focality.

focus:

The point inside the Earth's crust from which an originates.

foothills: A geographic transition zone defined by gradual increases in elevation between or low-relief and adjacent topographically higher hills,, or.

footslope: The part of the profile of a that forms the concave surface at the base of the slope. It is a transition area between sites of erosion and transport higher up the slope (e.g. the and ) and sites of deposition further down the slope (the ).

ford: A place, natural or man-made, where a river or stream is shallow enough to be crossed by wading, or by getting a vehicle's wheels wet (as opposed to crossing a permanently dry ). Fords may be seasonal or temporary, becoming impassable during high water.

foredeep: A relatively narrow, deep, elongated, and steep-sided trough in the, usually near or parallel to a mountainous land area or associated with an, or such a trough when infilled with sediment. See also.

foreland: Any land area or territory located in front of something else. A landform projecting into the sea, e.g. a or. The seaward trading area associated with a particular or. (glaciology) The area between the current leading edge of a and the of the most recent maximum.

foreland basin: A type of structural that develops adjacent and parallel to a as a result of lithospheric flexure during its orogeny. Topographic loading and downflexure creates space in the basin that is filled by sediment eroded from the range. Compare.

foreshore: The part of a located between the lowest and the. See also '; contrast '.

forest: Any extensive area dominated by communities of trees.

form line: A whose precise position on a map has not been accurately surveyed but rather from surrounding contours.

fresh water: Any naturally occurring water characterized by low concentrations (typically less than 0.05% by volume) of dissolved salts and other solids relative to either or brackish water. Sources of fresh water on Earth include,, , , , , , and most.

friction of distance: The influence and restraining effect of distance on all forms of movement, based on the fundamental geographical principle that movement necessarily incurs one or more costs, in the form of physical effort, energy, time, and/or other resources, and that these costs are directly proportional to the distance traveled. Such costs effectively resist the propensity for movement, akin to the friction of classical mechanics, and hence the concept of physical distance is a critical factor in determining whether or not a given movement, event, or process occurs.

frontalier:

Someone who lives in one country and works in a neighboring country, commuting across the international each workday and returning to their country of residence on a nightly or weekly basis; someone who lives and works across political or geographical.

frontcountry:

frontier: The area near or beyond a political or geographical ; a or borderland. The area near or beyond the edge of a settled or civilized area, consisting of sparsely populated or uninhabited wilderness. See also ' and '.

functional diversity: The characteristic of a place where a variety of different activities (economic, political, or social) occur, most often associated with places.

G
gallery forest: A narrow strip of trees or shrubs lining both of a river or stream in otherwise treeless, open country. Above very narrow streams, the foliage on each side may meet in the canopy.

gazetteer: A geographical dictionary or directory used in conjunction with a or and containing information concerning the geographical make-up, social statistics, and physical features of a,, or.

gentilic: See.

geoblocking:

geocode: A concise, human-readable series of letters, numbers, and/or other symbols used to represent and uniquely identify a particular geographic entity so as to distinguish it from other geographic entities in a finite set or database.

geocoding:

geocell: In many, an imaginary polygon on the surface of the Earth with dimensions 1 of by 1 degree of, or approximately 111 x at the , repesenting an area equal to about 12321 sqkm. The east-west distance equal to 1 degree of longitude gradually decreases as one approaches the poles, however, such that the shape of a geocell becomes increasingly trapezoidal at higher latitudes.

geodata:

Any data or information having an implicit or explicit association with one or more locations on the Earth, especially that used for in databases.

geodesic:

geodesy:

The science of accurately measuring and understanding the Earth's, orientation in space, and gravitational field and how these properties change over time.

geodetic control network:

geodetic datum:

A and set of reference points used for locating places on the Earth, which defines and  coordinates upon a particular  that approximates the. Geodetic datums are used in,, and applications to translate positions indicated on paper or digital  to their actual positions on the Earth; because the Earth is an imperfect ellipsoid, localized datums such as the ED50 covering only specific countries or regions are often more accurate representations of their area of coverage than global standards such as the WGS 84 of the.

geodetic north: See.

geodetics: See.

geodynamics: A subfield of geophysics and that studies the physical dynamics of the Earth by applying physics, chemistry, and mathematics to the understanding of how mantle convection and other internal processes lead to and geological phenomena such as mountain formation, volcanism, earthquakes, and, among others.

geofence: A virtual boundary or perimeter drawn around a real-world geographic area in a GIS software application, allowing distinctions between the properties of adjacent places which cannot be physically made on the ground to be made and stored digitally in an electronic database.

geographic coordinate system: A coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters, or symbols. Geographic coordinates are often chosen such that one of the numbers represents a vertical position such as and two or three other numbers represent a horizontal position such as and.

geographic information science (GIS):

The scientific study of data structures and computational techniques for capturing, representing, processing, and analyzing.

geographic information system (GIS): Any system of computer software tools designed to allow users to record, store, manipulate, analyze, manage, and present large sets of spatial or.

Geographic Names Information System (GNIS): A digital public-domain database developed by the U.S. Geological Survey and the U.S. Board on Geographic Names which contains name and locative information about more than two million physical and cultural features located throughout the United States and its territories. Each feature recorded in the database receives a unique feature called a GNIS identifier.

geographical inertia:

The tendency of a place with established installations and services to maintain its size and its importance as a focus of economic or industrial activity after the conditions originally influencing its development have appreciably altered, ceased to be relevant, or disappeared.

geographical mile: A unit of length defined as the distance equal to one minute of arc along the Earth's : approximately 1,855.3 m. The precise length varies with the used to approximate the. Regardless of the particular ellipsoid, the length of one of  at the Equator is equal to exactly 60 geographical miles.

geography: The scientific study of the lands, features, inhabitants, and phenomena of Earth.

geoid: The shape that the surface of the Earth's would take under the influence of Earth's gravity and rotational acceleration alone, in the absence of other influences such as winds and. It is often characterized as the precise mathematical : a smooth but irregular gravitational equipotential surface at every point of which, by definition, the direction of the force of gravity is always perpendicular and are always parallel. Its shape results from anomalies in the Earth's gravitational field caused by the uneven distribution of mass within and on the Earth's surface. A is an idealized approximation of the more complex and accurate geoid.

geoinformatics: The science and technology which develops and uses information science infrastructures to address problems and analyze data within,, , and related branches of science and engineering.

geoinformation: See.

geolocation: The identification or estimation of the real-world geographic of an object, involving the generation of a set of in order to determine a more meaningful description of location, such as a street address.

geolocking: See.

geomatics:

The scientific discipline that involves gathering, storing, processing, and delivering geographic or information.

geomorphology: The study of the arrangement and form of the Earth's and of the relationship between these physical features and the geologic structures beneath.

georeferencing:

geoscience: See.

geosophy: The study of geographical knowledge from any and all points of view, past or present, true or false; the study of the nature and expression of geographical ideas.

geospatial science: See.

geosphere: The collective non-living parts of the Earth: the, the, the , and the.

geostatistics: A branch of statistics which involves the organization, management, and analysis of spatial and spatiotemporal datasets. Geostatistical algorithms are often incorporated in software applications.

geosystems: See.

geotargeting:

ghetto: A section of a city occupied by members of a minority group who live there because of social restrictions on their residential choices. Originally, the term referred specifically to a section of a European city to which Jews were confined.

ghost town: A deserted or abandoned village, town, or city, especially one in which remaining buildings and infrastructure such as roads are still visible. The term is also sometimes used to refer to settlements that are still populated, but significantly less so than in previous years.

glacial: Of or pertaining to a or to the consequences of ; formed, deposited, caused, or affected by processes.

glacial drift: See.

glacial flour: See.

glacial lake: A or other enclosed created by historical or ongoing  activity; e.g. the Great Lakes of North America.

glacial till: The mass of rocks and finely ground material carried by a and deposited when the ice melts. This creates an unstratified material of varying composition.

glacial trough:

glaciation: The process or state of being covered with a. Another name for a glacial period, an interval of time that is marked by colder temperatures and advancing glaciers.

glacier: A persistent mass of dense ice that is constantly moving under its own weight, and which is composed largely of compacted snow that forms where the annual accumulation of snow exceeds its melting and sublimation over very long periods of time. Glaciers slowly deform and abrade the land beneath them, creating a huge variety of landforms including,, and. They form exclusively on land and are distinct from the much thinner ice that forms on bodies of water.

glaciology: The scientific study of, including their formation, composition, behavior, causes, effects, and distribution; or more generally of ice or any natural phenomena involving ice.

glacis: A smooth, gently sloping surface at the foot of a,, or any other high , whether natural or artificial. In the latter case, the term is used in particular to describe a stone or earthen constructed at the base of some historical military fortifications.

glade:

Any large, open, mostly treeless area within a.

glen: A long bounded by gently sloping, concave sides, and typically narrower and deeper than a. The term is used primarily in Scotland.

glint: A steep, terrace, or edge of a.

global: Of or concerning all parts of the world (i.e. worldwide); affecting or distributed across the whole of the Earth. Of or relating to a or sphere; spherical. Comprehensive; total; encompassing all or nearly all considerations, categories, items, etc.

global city:

A which functions as an important or primary node in the global economy. Though criteria are not strictly defined, a global city typically is very large; dominates trade and economic interactions within a large surrounding area; supports a large and demographically diverse population; serves as a center of ideas and innovation in business, science, culture, and politics; and/or is a headquarters for major financial institutions, multinational corporations, or worldwide media and communications networks.

global navigation satellite system (GNSS):

Global Positioning System (GPS): A -based owned and operated by the United States Department of Defense and made available for use by both the military and the general public. It is one of several standards that provides  and time information, transmitted via microwave signals, to enabled, known as GPS receivers, anywhere on or near the Earth where there is an unobstructed line of sight to at least four GPS satellites. Modern state-of-the-art GPS receivers can accurately pinpoint locations to within 30 cm.

globalization: The process of interaction and integration among people, companies, governments, and cultures across the world. A complex and multifaceted phenomenon, globalization is considered largely the result of economically motivated advances in transportation and communication technologies in the past several centuries which have dramatically increased interactions between otherwise isolated groups of people.

globe: A true-to-scale of the Earth that duplicates its round shape and correctly represents relative areas, sizes, and shapes of physical features, distances, and directions.

gnamma: See.

gore: An irregularly shaped of land of any size, often approximately triangular, that is left between two adjoining parcels as the result of incomplete or inaccurate  surveys. A lune-shaped which may be fitted to the surface of a with a negligible amount of distortion.

gorge: See.

graben: A or bounded on either side by distinct, parallel  or  and formed by the downward displacement of a block of the Earth's. Grabens often occur side-by-side with, their uplifted or non-displaced counterparts, in a repeated series of vertical displacements.

grade:

A physical surface that is inclined with respect to the horizontal, or the angle between that surface and the horizontal, typically expressed in degrees, or calculated as a ratio of "rise" (vertical distance) to "run" (horizontal distance) and expressed as a fraction or percentage; a larger number indicates a steeper incline. The term "grade" is often used to describe the incline of man-made surfaces such as roads and the roofs of buildings, whereas the term "slope" is more commonly used to describe natural surfaces such as the sides of or or the  and  of.

grassland: Any land area where the vegetation is dominated by grasses (i.e. plants of the botanical family Poaceae), sometimes also inclusive of grass-like plants of other families. A large and important occurring worldwide, grasslands may be natural or created for agricultural purposes.

graticule: A network of lines on a or (or imagined on the surface of the Earth) representing geodetic  of  and  of.

gravimetry: The measurement of the strength of a gravitational field, especially the Earth's gravitational field, typically by calculating the acceleration due to gravity at a particular point on the Earth's surface. Because it can vary widely across the surface, knowing the local magnitude of the gravitational force is often necessary in order to produce accurate geographical data.

great circle:

Any circle on the surface of a sphere created by the intersection of the sphere and a plane that passes through its center. A great circle divides the sphere into two equal hemispheres, and all of a sphere's great circles have the same center and circumference, which by definition is the largest possible circumference of the sphere. The mathematical properties of great circles make them useful in, where they are often visualized upon the surface of the Earth (despite the fact that the Earth is ): for example, the of the idealized Earth is a great circle, and any with its  forms a great circle. Because the shortest path between any two points on the surface of a sphere follows the arc of a great circle, are often used as approximations of  for the purposes of air and sea navigation. See also.

great-circle bearing: The horizontal direction or followed by the arc of a through a given pair of terrestrial points, expressed as the angular distance from a reference direction.

great-circle distance:

The length of a line between two points which follows the arc of a as defined by the intersection of the Earth's surface with an imaginary plane passing through the Earth's center. It is the shortest route between those two points on the Earth's surface.

green belt:

A special land-use designated in some cities to prevent development of wild, largely undeveloped, or agricultural land surrounding or adjacent to areas, in order to conserve natural ecosystems, to allow the return and establishment of wildlife, and/or to create  for aesthetic or recreational purposes. The term may also refer more specifically to the boundary between developed and undeveloped areas rather than to the undeveloped area itself.

greenfield: A previously undeveloped plot of land for which development is proposed or on which it is in progress.

grid: A pattern of lines on a or, such as those representing and, which helps determine.

grid magnetic angle:

The angular difference in direction between and, typically expressed in degrees east or west of grid north.

grid north: The direction northwards as indicated by the of a, which may or may not be aligned with and.

grivation: See.

groundwater: The water present beneath the Earth's surface in soil pore spaces and in fractures and voids within geological. Contrast.

grove: A small group of trees growing close together and generally surrounded by little or no undergrowth.

growing season: The part of the year during which local weather conditions (i.e. temperature and precipitation) permit the normal growth of plants in a given location. What defines a "growing season" is often informal and colloquial, and may vary widely by location and from year to year; in many places, the local growing season is defined as the period of time between the average date of the last frost (in temperate parts of the, this typically occurs in the spring) to the average date of the first frost (in the autumn).

groyne: A rigid, man-made hydraulic structure extending from an ocean or river, constructed to interrupt water flow and limit the movement of sediment by.

gulch: A deep, V-shaped formed by erosion, often containing a small stream or a dry, especially one in arid regions.

gulf: A large arm or of an or  that lies within a curved coastline, similar to a  but usually larger and often with a narrower opening.

gully: A landform resembling a large ditch or a small created by the action of swift running water eroding deeply and sharply into soil, typically on a hillside.

gumbo: Any very fine, clayey soil which rapidly turns to sticky mud when wet. The term is used primarily in the United States and Canada.

guyot:

An isolated underwater with a flat top that is at least 200 m below the water's surface.

gypsey: See.

gyre: Any large system of circulating, particularly those related to large-scale wind movements. Gyres are caused by the and play a fundamental role in the global.

gyroscope: A device consisting of a spinning disc or rotor mounted in such a way as to preserve the orientation and angular velocity of its axis of rotation with respect to an inertial reference frame, irrespective of perturbations to the mounting itself, which makes it possible to measure and maintain an unbiased equilibrium in the and/or of a moving object such as an airborne or waterborne vehicle or camera. Modern digital gyroscopes and their associated readouts are widely used in and  as the basic sensor in -seeking, direction-keeping, and attitude stabilization systems.

H
habitus: An individual's sense of "home", or of their place in the world, comprising socially ingrained habits, beliefs, skills, and dispositions based on their geographical environment, cultural origin, inheritance, experiences, and the social networks they develop throughout their life, all of which may be subject to refashioning with passing time or increasing distance.

hachure: Any of a series of non-numerical lines used on a to indicate the general orientation and steepness of. Such lines vary in length, thickness, and spacing, with steeper slopes indicated by shorter, heavier, and more closely spaced lines.

haff: A coastal of or  on the south coast of the Baltic Sea, fed by a stream which is blocked by a, through which it is linked to the sea by a.

halo effect: In the context of geography, the detrimental effect of a or other boundary on locations close to it, making those locations unattractive to people intending to visit or settle there; e.g. a political boundary in disputed territory, where immigration across the boundary occurs frequently. There may also be beneficial effects on such locations.

ham: In southern England, a plot of meadow land, especially a tract of rich pasture near a river; or a small settlement, ranging in size from a single to a.

hamada:

A landscape consisting of high, largely barren, rocky where most of the sand has been removed by, and thus lacking most surficial materials other than boulders and exposed.

hamlet: A small human settlement, variably defined as one the size of a,, or or as a smaller subdivision of or satellite entity to a larger settlement.

hanging valley: A that is higher in elevation than the main valley into which it drains, such that it appears to be "hanging" above the lower valley. Hanging valleys are commonly the result of differential erosion, when adjacent areas beneath a glacier are subjected to different rates of erosion.

harmonic tremor: One of a series of continuous rhythmic in the Earth's upper that can be detected by. Harmonic tremors often precede or accompany.

head of navigation: The farthest point above the of a that can be navigated by watercraft, whether because of natural or man-made obstacles.

heading: The in which the bow or nose of a moving vessel or aircraft is pointed. This is not necessarily the same direction in which the vessel is actually traveling, known as its ; any difference between heading and course is due to the motion of the air or water through which the vessel is moving, or other aerodynamic effects such as skidding or slipping. See also.

headland: A high coastal that extends out into a body of water, often surrounded by steep. A very large headland is often called a.

headwall: A steep slope or sheer cliff face at the upper end of a (e.g. at the back of a ), or at the active face of a mine, pit, or.

headwaters: Another name for the of a,, or other , i.e. the point or points furthest from the of a particular stream, at which precipitation, , or  first accumulates into a persistent, identifiable, and/or named  whose contents ultimately empty into the particular stream; or all of the uppermost streams of a  considered collectively (of which there may be thousands), typically including all streams identified as first-order through third-order in conventional  systems. The entire, inclusive of land, surrounding these sources, often abutting the boundary of a that separates different watersheds.

hearth: The source area of any innovation. The source area from which an idea, crop, artifact, or good is diffused to other areas.

heartland: The central or interior part of a. A part of a region considered essential to the viability and survival of the whole.

heath:

A shrubland habitat found mainly on free-draining, infertile, acidic soils and characterized by open, low-growing, woody vegetation.

hectare (ha): A metric unit of area defined by a square with sides of 100 metres, equal to 10,000 m2 or 2.471. There are 100 hectares in 1 square kilometre (km2).

hedgerow:

A line of closely spaced shrubs or trees, planted and trained so as to form a barrier, to mark the boundary between two neighboring areas, or to serve as a windbreak for crops in adjacent fields.

heliotrope: A device used in to reflect sunlight onto a distant point so as to aid long-distance observations.

hemisphere: One half of the Earth, usually conceived as resulting from the division of the globe into two equal parts of either and or  and.

heteroclinal fold: A geological of which one side is sloped at an angle steeper than that of the other side.

high plain: A lying at a high, generally above 600 m.

high water mark: A natural or man-made demarcation that indicates the maximum rise of a over land. Though not necessarily an actual physical mark, river or sea waters rising to a high point often leave a lasting physical impression such as a noticeable discoloration or deposition of debris; such a mark is often the result of a flood or storm surge. High water marks may reflect an all-time high, an annual high, or the high point for some other division of time (e.g. a cycle). A natural delineation created by debris deposited by a high tide is called a. See also ' and '.

highland:

Any elevated region of land, often one that is or situated atop a. The term is sometimes reserved for relatively low-elevation or. Any area of land (mountainous or otherwise) that is higher in relative to another area. In this sense, the term is often used as a conditional descriptor to distinguish related habitats or ecosystems, especially freshwater, on the basis of elevation above sea level.

highway: Any major public or private road or other thoroughfare on land, especially one that is paved and capable of supporting high-capacity, rapid transit between.

hill: Any landform that extends above the surrounding. A hill is generally considered less steep than a.

hillock:

A small.

hinterland: An area that is tributary to a place and linked to that place through lines of exchange or interaction. The area, not necessarily settled itself, that is nonetheless influenced by a particular or establishment, i.e. its.

historical geography: A branch of that studies the ways in which geographic phenomena have changed over time, especially (though not necessarily limited to) geographic change as it relates to human activity; the geography of the past, whether real, perceived, or theoretical.

hoe: A projecting or of land, its height ending abruptly or steeply. The term is used primarily in in Great Britain.

hogback:

A long, narrow or series of with a narrow crest and steep, symmetrical slopes of nearly equal inclination on both flanks, especially one created by the differential erosion of an  which exposes homoclinal sedimentary rock strata. Compare ', ', and.

holding: Land owned or occupied by legal right for the purpose of agriculture.

homestead: (dwelling) A house or home, especially an isolated farmhouse with its associated outbuildings on a large agricultural holding such as a ranch; or a small settlement of dispersed farms. (legal concept) In the United States, a plot of land given legal meaning by a series of federal laws granting applicants ownership of land in the public domain upon the condition that they live on it and it. Homesteaders were initially granted plots of 160 acre, which was considered adequate to support a single family, but later as much as 640 acre.

horizon:

The apparent line that separates the ground from the sky, dividing all visible directions into two categories: those that intersect the Earth's surface and those that do not. When not obscured by buildings, trees, or mountains, the true horizon can be useful in navigation and determining positional orientation. In perfect visibility, to an observer on Earth standing at an elevation of 3 m from the horizontal, the horizon in any direction is approximately 6.5 km distant; at 30 m, it is 21 km away.

horizontal equivalent: The distance between two points on a land surface when projected on to a perfectly horizontal (i.e. flat) plane, e.g. on a, as opposed to measuring the actual physical length along the real-world surface, which can be greatly increased by and other topographic variations. The distance between the start and end points of any route, even if at the same elevation, will often appear to be much shorter on a map than the shortest route that could actually be walked between them, because of the influence of real-world changes in vertical displacement along the path followed by the route.

horn: A formed by the back-to-back abutment of three or four adjacent, leaving a distinctly pyramidal peak.

horst: A raised block of the Earth's, bounded by parallel or, that has been displaced upward or has remained stationary while adjacent blocks on either side, known as , have been displaced downward. Horsts and grabens often occur side-by-side in a repeated series of vertical displacements.

hotspot: An area in the middle of a where rises from the  and erupts at the Earth's surface, despite being far from the plate's  boundaries. often occur above a hotspot.

hum: A residual hill in limestone country, resembling a haystack, left standing when the surrounding land surface is eroded.

human geography: The branch of geography that studies humans and their communities, cultures, economies, and interactions with the environment by examining their relations with and across space and place. Along with, it is one of the two major sub-fields of geography.

humanistic geography:

An approach in which emphasizes the subjective as distinct from the objective in that it stresses the importance of perception, creativity, thinking, and beliefs as well as human experience and values in the formation of the attitudes of people toward their environment and in affecting their relationships with it.

hummock: A small or, typically less than 15 m in height and situated above an otherwise level ground surface.

humus: Partially decomposed organic soil material.

hundred: In England, Scandinavia, and many other parts of the world, an administrative subdivision of a larger region, often a or, with its own judicial authority.

hydrograph: A graph showing the rate of flow (i.e. the ) of water past a specific point of measurement in a river or other channel over time, typically expressed in cubic metres or cubic feet per second (m3 or ft3/s).

hydrography: The study of the surface waters of the Earth.

hydrosphere: The totality of the water found on, under, and above the Earth's surface in liquid, solid, and gaseous forms, including all,, , and , as well as all ice and and subsurface. Some definitions restrict the hydrosphere to liquid water only, instead placing solid forms in the and gaseous forms in the.

hypsography: The geographic representation on a of features related to,, and other measures of height above a reference surface (and sometimes inclusive of depths below the reference surface as well).

hypsometer: Any instrument used to measure the height or of an object above a reference surface, either by trigonometry or by measuring changes in atmospheric pressure or boiling point. Trigonometric principles are applied when viewing the measured object from a distance, e.g. when determining the heights of trees or buildings, or when the elevations of distant landforms; whereas the principle that atmospheric pressure decreases predictably with elevation above  is applied in instruments that measure their own height (i.e. the elevation of the instrument's location).

hypsometry: The study or measurement of the or depth of features of the Earth's surface relative to mean. In a narrower sense, hypsometry may refer to land elevations only, and therefore is sometimes viewed as the terrestrial equivalent of.

I
ice age: Any very long period of Earth's history during which surface and atmospheric temperatures are greatly reduced, resulting in the development or expansion of continental and and widespread. The most recent such period was the Pleistocene Epoch, which ended approximately 12,000 years ago.

ice cap: A flattened, often dome-shaped mass of ice that covers less than 50000 sqkm of land area and is not constrained by topographical features such as mountains; larger masses of ice are termed. Contrast.

ice floe: A large piece of floating, typically with a flat surface and at least 20 m across at its widest point.

ice sheet:

A mass of ice that covers more than 50000 sqkm of land area; smaller masses of ice may be termed or. The two are the only ice sheets that currently exist on Earth.

ice shelf: A large floating platform of ice formed when a or in a  area flows onto the  surface. By contrast, is formed directly over the water and is typically much thinner.

ice stream: A region of relatively fast-moving ice within an that flows like a stream under its own weight (making it essentially equivalent to a ) and empties into the ocean. Ice streams are responsible for the majority of the mass lost from both the Antarctic and Greenland ice sheets.

iceberg: A large chunk of ice which has broken away from a larger body of ice (such as a or ) and is floating freely in open water.

icefall: A portion of a where a steepening or narrowing of the underlying bed causes the ice to move more rapidly than elsewhere, resulting in a chaotic, highly fractured surface characterized by numerous and.

igneous rock: Rock formed when molten (melted) materials harden.

impact crater: A type of formed by the hypervelocity collision of a solid astronomical body, such as a meteor, with the Earth's surface. Unlike, impact craters typically have raised rims higher in elevation and depressed floors lower in elevation than the surrounding terrain.

impoundment: Another name for a that impounds a. The created by such a dam.

improved land: Any land area which has been intentionally altered from its natural condition by human activity, such as ploughing, clearing, cultivation, or some other form of management, and thereby made more valuable or productive for human purposes (not necessarily to the benefit of any other organism or the environment in general). Legal definitions vary with location, but in most countries the term refers primarily to certain types of agricultural land or to property which has been developed for residential or commercial use.

inclinometer:

An instrument used to measure angles of,, or with respect to the direction of the gravitational force, i.e. in the vertical plane, including both inclines and declines. The measure may be expressed in degrees, percentage points, or topos.

index contour: A drawn with a heavier line weight to distinguish it from intermediate contours. Depending on the, index contours are usually indicated every fourth or fifth contour, along with their assigned numerical values, in order to facilitate ease of interpretation.

index map: See.

inertia costs of location: Costs borne by an activity because it remains located at its original site, even though the distributions of supply and demand have changed.

influent: (of a stream, river, or any natural water flow) Flowing into a larger watercourse or body of water.

infrastructure: The broad set of facilities and interrelated systems that serve a,, or any other inhabited area, encompassing the structures and services necessary for its industries, economies, and residential spaces to function, i.e. for the human population occupying these spaces to get what they want or need when they want or need it. Infrastructure may include public and private physical structures such as roads, railways, bridges, tunnels,, , sewers, and electrical and telecommunications networks, among other things. A well-developed infrastructure is essential to enable, sustain, and improve living and working conditions in any society or organization.

ingression coast:

A generally flat whose shape has been largely defined by the penetration of the sea into relatively low-lying areas of the land surface, often as a result of movements or a rise in, such that the boundary between land and water closely matches the topographic contours of the land prior to its being covered by seawater.

inland: Of, relating to, within, or towards the interior of a, i.e. distant from the.

inland sea: A very large, isolated expanse of open water in the interior of a, either completely surrounded by dry land or connected to the by a river,, or other narrow.

inland waters: Any surface or surrounded entirely by land, including,, , and , or all such waters within a polity considered collectively. See also.

inlet: An indentation of a, usually long and narrow, which leads to an enclosed body of, such as a , , , or.

inselberg:

An isolated rocky, knob,, or small that rises abruptly from a virtually level surrounding. Compare.

inset: A subsection of a that is reserved for depicting another map of the same place at a different, often a smaller scale to show relative within a larger geographic area (e.g. a country's location on the ) or a larger scale to show increased detail (e.g. of public transit routes in a ), or with different features or overlays in order to provide additional information that would be difficult to interpret if presented in the main map area. Insets are usually outlined with an obvious boundary to prevent confusion, and may include their own set of cartographic elements such as a scale,, and.

inshore: (relative to a position on a body of water) Near to or moving towards the ; shorewards of a position as opposed to seawards of it. See also ' and '.

insular: Of or relating to an, or suggestive of the isolated condition of an island.

integrated drainage: A drainage pattern in which systems have developed to the point that all parts of the landscape drain into some part of a stream and to a common base level, the initial or original surfaces having essentially eroded away entirely, such that few or no  are present.

integrated geography:

The branch of geography that describes and explains the spatial aspects of interactions between human individuals or societies and their natural environment.

intercardinal directions:

The set of four intermediate directions used in and, each of which is located halfway between a pair of : northeast (NE), southeast (SE), southwest (SW), and northwest (NW). They are often included in the and are used to define further subdivisions such as the.

interfluve: A narrow, elongated, and -like or -like landform between two, or an area of higher ground between two rivers in the same.

intermediate directions: See.

intermontane:

Situated between or, e.g. the high lying between the eastern and western ranges of the Andes.

International Date Line: A line of generally 180 degrees east and west of the. The date is one day earlier to the east of the line.

international waters:

interpolation: In, the estimation of the values of at unsampled points based on known values of surrounding points, under the assumption that any unknown quantity can be calculated based on its distance to each surrounding quantity. Interpolation techniques such as spline and are commonly  operations, but can also be applied in  environments using a  to model a surface.

interruption: Any place where the contiguous geographic area represented in a has been split, separating to distant parts of the projection certain features and locations which are in reality much closer to each other, in order to permit the representation of a three-dimensional space on a two-dimensional map. All, for example, have at least one interruption, conventionally along the length of a single, thus forming an east–west boundary despite that the approximately spherical is continuous, with no such boundaries; features on either side of the interruption, though very close to each other on the actual Earth, are depicted on opposite edges of the map, appearing to be separated by thousands of miles. Some world map projections attempt to reduce distortion of scale by having more than one interruption, which divide the projected area into multiple, each with its own central meridian.

intervening opportunity: The existence of a closer, less expensive opportunity for obtaining a good or service, or for a migration destination. Such opportunities lessen the attractiveness of more distant places.

Intracoastal Waterway (ICW): A system of navigable inland channels, maintained through dredging and sheltered for the most part by a series of linear offshore islands, that follows the Atlantic and Gulf Coasts of the United States more than 4800 km from Boston, Massachusetts, around the southern tip of Florida, to Brownsville, Texas.

inversac: See.

inverted river delta:

island:

Any piece of sub-continental land that is entirely surrounded by water; or more generally, any isolated habitat that is surrounded by a different habitat, including different types of land.

island nation: A or polity whose territory consists primarily or entirely of one or more or parts of islands.

isle: See.

islet: A very small.

isometric: Having equal measure.

isopleth: Any line on a connecting places of equal value of some specified variable. The variable may be a physical or natural quantity, such as elevation above sea level (as with ) or temperature (as with isotherms), or a quantity related to social or economic statistics, such as population, wealth, or transport costs.

isostasy:

The state of gravitational equilibrium between the Earth's and its, such that the crust "floats" at an that depends on its thickness and density. This concept is invoked to explain how different heights can exist at Earth's surface. Isostatic theory maintains that where equilibrium exists at the surface, equal mass must underlie equal surface area, and that the thickness of crustal features and the depth of the world's tend to change over time in order to compensate for the uneven distribution of mass in the. For example, the instability of where high mountains are found adjacent to deep oceanic trenches is explained by the subterranean movement of magma to effect a return to regional equilibrium, a process known as isostatic adjustment.

isthmus: A narrow piece of land two larger land areas across an expanse of water by which they are otherwise separated.

J
jetty: Any man-made structure that projects from land out into a body of water, serving as a, a walkway, or a landing stage for watercraft, or, in pairs, as a means of constricting a.

jhum cultivation:

Clear-cutting and/or setting fire to an area of land so it can be used for farm cultivation.

junction: A meeting or intersection of two or more routes of travel, as of roads, rivers, or lines on a map, or a place at which a single route diverges into two or more different routes.

jungle: An area covered with dense vegetation dominated by large trees, often tropical.

jurisdiction: The right and power to apply the law in a particular place or within a defined field of responsibility. The geographical area to which such authority applies.

juvenile water:

K
kame: An irregularly shaped or composed of sand, gravel, and  which accumulates in a depression on a retreating  and is subsequently deposited on the land surface with further melting of the glacier. Kames are often associated with.

karre: A furrow or varying in depth from a few millimetres to more than a metre, and separated from others by, caused by solution on limestone surfaces.

karst: An area possessing surface resulting from the underground solution of subsurface limestone or dolomite.

kettle:

A shallow, sediment-filled body of water formed by blocks of ice calving from a retreating, or by draining floodwaters.

key: See.

key col:

kill:

A river, stream,, or tidal. The term is used primarily in areas of Dutch influence in the northeastern United States.

knickpoint:

A point of abrupt inflection in the longitudinal profile of a or its or, such as occurs at a. Any interruption or break in the character of a.

knob: A peak or projection from the top of a or, or any rounded protrusion of land, especially a small but or  hill with steep sides; a boulder or an area of  protruding from the side of a hill or mountain. The term is used primarily in the southern United States.

knoll: See.

kolk:

A violently rotating underwater vortex capable of and scouring in, which may leave behind distinct pits or lakes known as  or. Another name for a.

kopje: See.

krai: In Russia and other Slavic countries, a generic term for a, historically and politically reserved for regions in particular, and variously translated as, , or. The term is cognate with the name of Ukraine.

kriging:

In, an technique in which, for a given, a predicted value for an unmeasured location is derived by weighting the surrounding measured values based on the distance between them and to the unmeasured location, as well as the overall spatial arrangement of the measured points. Widely used in applications, kriging is based on regionalized variable theory, which assumes that the spatial variation in the data being modeled is homogeneous across the surface.

kum: A sandy of Central Asia, roughly equivalent to the Saharan.

kyle: In Scotland, a narrow or between two, or between an island and the.

L
lacustrine: Of or pertaining to a ; formed by or deposited in a lake.

lacustrine plain: A nearly level land area formed by the infilling of a with sediment and the complete drainage or evaporation of water from the lake, leaving the deposited sediments behind.

lagoon: A small area of water connected to the but otherwise blockaded by one or more.

lahar: See.

lake: A localized in a and surrounded entirely by land. Lakes are often defined as separate from any or stream that serves to feed or drain them.

land bridge: Any piece of land connecting larger land areas that are otherwise separated by water, especially one over which living organisms, such as terrestrial animals and plants, are able to cross and thereby colonize previously inaccessible lands. Land bridges may be created by falling sea levels,, or post-glacial rebound. Compare.

land cover: The physical material present on the surface of the Earth, including categories such as vegetation (grasslands, shrubs, forests, etc.), bare ground, water, asphalt and artificial surfaces, and many others.

land-fast ice: See.

landform: A natural feature of the solid surface of the Earth. A combined set of landforms makes up the of a given area, and their arrangement in a landscape is known as.

landlocked: (of a country or other polity, or a geographical region) Completely surrounded by land and thus lacking a marine ; having no territory directly connected to or bordering the. (of a property or parcel of land) Completely surrounded by privately owned property and having no access to a public road.

landmark: Any natural or artificial feature that is recognizable enough to be used for ; a feature that stands out enough from its environment to be visible across long distances.

landmass: Any large contiguous area of land typically surrounded by an or. Compare.

landscape: A broad or distinct area of land consisting of a collection of which define a general form or setting, e.g. a,, , , etc. Landforms within a landscape are spatially associated but may vary in formation processes and age. The visible features of an area of land, its landforms, and how they integrate with natural or man-made features. In the broadest sense, landscapes may include geophysical landforms such as hills and mountains; such as rivers, lakes, and the sea; living elements of such as vegetation; human elements such as buildings, structures, and various forms of ; and transitory elements such as lighting and weather conditions. They reflect both physical origins and the cultural overlay of human presence in a living synthesis of people and place.

land-tied island: See.

lateral blast: A sideways-directed explosion from the side or summit of a.

lateral moraine:

latitude: A measure of distance north or south of the. One degree of latitude equals approximately 110 km. Lines of latitude, also called or parallels, are the imaginary lines that cross the surface of the Earth in an east-west direction (parallel to the Equator) and measure how far north or south of the Equator a place is located.

lava: The term used for once it has erupted onto the Earth's surface.

layer of no motion: In, a hypothetical layer at some depth in the ocean within which the water is assumed to be at rest, implying that the isobaric surfaces within that layer are level and hence that such surfaces can be used as points of reference when calculating absolute-gradient.

lea: A pasture,, or grassy.

leaching: A process of soil nutrient removal through the erosive movement and chemical action of water.

lee: The side or of a physical feature (such as a or ) which faces downwind, i.e. away from the direction in which the wind is blowing, or which faces away from an advancing  or. The lee side is often sheltered by the topography from exposure to the wind and any moisture it brings.

leeward: Toward the side; sheltered from the wind; the direction downwind from a point of reference. Contrast.

legend: A key for understanding the meanings of the symbols or pictures on a.

LEDC: An acronym for Less Economically Developed Country.

levee:

An elongated naturally occurring or an artificially constructed wall or barrier which regulates water levels in areas prone to flooding. It is usually earthen and often parallel to the course of a or a.

lithosphere: The Earth's hard, outermost shell. It comprises the crust and the upper part of the mantle. It is divided into a mosaic of 16 major slabs or plates, which are known as or.

lithospheric plates:

A series of rigid slabs (16 major ones at present) that make up the Earth's outer shell. These plates float on top of a softer, more plastic layer in the Earth's.

loam: A type of easily worked, highly fertile soil composed of clay, silt, and sand in an approximate ratio of 20:40:40. Loams generally heat rapidly, are well-aerated, and drain neither too quickly nor too slowly.

location: A particular point or place in physical space. Compare.

location theory: A group of theories which seek to explain the siting of economic activities in particular.

loess: A soil made up of small particles that were transported by the wind to their present location.

longitude: A measure of distance east or west of the, a line drawn between the and and passing through the Royal Observatory at Greenwich, England. Lines of longitude, also called, are the imaginary lines that cross the surface of the Earth in a north-south direction (parallel to the Prime Meridian) and measure how far east or west of the Prime Meridian a place is located.

longshore drift:

A geological process by which sediment is transported along a parallel to the due to incoming wind-driven waves meeting the shore at an oblique angle; this generates a water current which moves unidirectionally along the shore within the. A well-known example occurs on sandy when  send swash up the beach at an angle but gravity drains the  straight downslope, perpendicular to the shoreline, causing the same sand particles to gradually move down the beach over multiple cycles. The same process occurs at many different scales and affects all sediment sizes, and can vary with the wind direction even at the same location.

lowland: Any area of land that is lower in relative to another area. The term is often used as a conditional descriptor to distinguish related habitats or ecosystems, especially freshwater, on the basis of elevation above sea level. Lowland areas are usually relatively flat and characterized by slow-flowing waterways and. Contrast ' and '.

M
maar: A broad, shallow, flat-bottomed created by an eruption involving coming into contact with. Maars commonly have low rims and subtle and characteristically fill with water to form.

machair: A fertile, low-lying, grassy on the northwest of Ireland and Scotland.

magma: Molten rock containing liquids, crystals, and dissolved gases that forms within the upper part of the Earth's and. When erupted onto the Earth's surface, it is called.

magmatic water: See.

magnetic anomaly: A local deviation from the predicted value of the, due either to the presence of rocks formed in past geological eras which have preserved internal magnetizations that differ from modern magnetic alignments, or to local abundances or deficiencies of ferromagnetic minerals.

magnetic declination:

The angle on the horizontal plane between and. Because needles always point to magnetic north, and because the  and the  are not in precisely the same location, the north direction indicated by a compass may be slightly different from the direction of geographic north, depending on the user's location on the Earth. The user can compensate for this discrepancy by adding the known declination angle for their location to the magnetic reported by their compass, yielding the true bearing with respect to true north.

magnetic dip:

The angle made with the horizontal by the. Locations in the usually have positive values of inclination, indicating that the magnetic field is angled downward, into the Earth; the angle increases as one approaches the, where the field lines point vertically downward, perpendicular to the horizontal. Locations in the usually have negative inclination, indicating that the field lines are angled upward, away from the Earth, with the maximum angle located at the. Dip angle is in principle the angle made by the needle of a vertically held, though in practice ordinary compass needles may be deliberately weighted against dip, or may be unable to move freely in the correct plane. Magnetic dip can be measured more reliably with a.

magnetic meridian:

magnetic north: The direction a points, towards the. Magnetic north differs from and.

magnetic pole: Either of the two poles of the Earth's true – the or the.

magnetic variation: See.

main stem:

The primary downstream of a, as contrasted with its. Virtually all of the water in a river's eventually flows through the main stem.

mainfall: See.

mainland: A term used to denote a or political territory relative to its politically associated but geographically remote. It is variously used to refer to the (i.e. non-) part of a polity relative to its  or oceanic islands; or to the largest or most politically, economically, and/or demographically significant island within an. For example, continental Europe is often considered "the mainland" relative to the British Isles, while the island of Great Britain is considered "the mainland" relative to Northern Ireland and the many smaller islands that constitute the United Kingdom.

makhtesh: A deep, closed (usually drained by a single ) surrounded by steep walls of resistant rock and superficially resembling a. The term is used primarily in the deserts of Israel and Egypt.

mammilated: Smooth and rounded in appearance, used of various landforms of different sizes from individual rocks to entire landscapes.

mantle: The layer of the Earth's interior between the and the, consisting of ultrabasic rock which is predominantly solid under the immense pressure of overlying rock but behaves as a viscous fluid over geological time scales or if this pressure is relieved (as with penetrating the crust). The mantle is about 2,900 km thick, making up 84% of the Earth's volume and 67% of its mass. The uppermost sub-layer is known as the ; the is composed of the topmost 65 – of the mantle and the crust.

map: A picture of a drawn at an established on a two-dimensional plane surface, often depicting natural and manmade features on or under the surface of the Earth or other planetary body, typically with the features positioned as accurately as possible relative to a ;  more generally, any graphical representation of locative information about the relative  of particular features within a space or place.

map index:

A graphical key identifying the relationships between the individual of a, their coverage areas, and/or their production status or availability. Index maps enable users to find a map or set of maps covering a particular region of interest by overlaying a grid or a set of rectangles on a map of a larger geographical area. Each grid unit or rectangle is labeled with a name or number corresponding to a specific which depicts the indicated area in greater detail.

map projection: A systematic transformation of the and of locations from the surface of a three-dimensional shape, such as a sphere or an ellipsoid, into locations on a two-dimensional plane. of locations on the Earth require map projections to represent features in a convenient format that is easy to view and interpret, though all map projections necessarily distort the true properties of the Earth's surface to some degree.

map series: A group of topographic or thematic usually having the same and  specifications and collectively identified by the publisher or producing agency as belonging to the same group.

map sheet: An individual or printed on a single page or sheet of paper, either complete in itself or part of a.

mapping: The process of designing, drawing, or creating a. The term is used in particular to refer to the application of techniques in order to make or, but may also be used for any map, and in the broadest sense may refer to the gathering of geographical data of any kind.

march:

A,, or , as opposed to an interior. In medieval Europe, a march was the land surrounding a border between realms, or a neutral under the joint control of two or more realms with conflicting laws or territorial claims.

margin: The line or edge along which the surface of a body of water meets the land. In property law, the of a piece of land which is bounded by a or, often with the center of the stream or the  defining the legal boundary. The mostly blank, unused space lying beyond the of a map and completely surrounding the map area. See also.

marginal land: Land that is of low agricultural value because any crops produced from it would be worth the same or less than the costs paid to produce them, either because the rights or required to cultivate it are very expensive, or the market prices for the crops are very low, or for any other reason. A change in economic conditions may allow formerly marginal lands to become profitable again.

marginal sea: A or other large area of the that is partially enclosed by land and/or  yet still adjacent to, widely open to, and connected to the larger ocean at the surface; e.g. the Yellow Sea and Hudson Bay. Those waters along a 's within which the nation has exclusive jurisdiction except for the right of innocent passage of foreign vessels. See also.

marine: Of, relating to, found in, or produced by the or. Of or relating to shipping or navigation, particularly by watercraft.

maritime climate: A climate strongly influenced by an environment, typically found on and the  shores of. It is characterized by small daily and yearly temperature variation and high relative humidity.

market orientation: The tendency of a firm or industry to be located close to wherever demand for the commodities it produces is strongest.

marsh: A type of dominated by herbaceous rather than woody plant species and often found at the edges of lakes and streams, where it forms a transition between aquatic and terrestrial ecosystems.

Massenerhebung effect:

massif: Any section of the Earth's which is demarcated by or flexures and tends to retain its internal structure while being displaced as a whole. A single large mass or compact group of connected mountains forming an independent portion of a.

mayen: In Switzerland and the Central Alps, a large shelf or ledge, intermediate between high alpine meadows and valley floors, where cattle are allowed to rest briefly during their annual movements between summer and winter pasture.

mean sea level (MSL): The average of one or more of the Earth's coastal bodies of water, such as and, or at a particular location, from which heights such as  and  are measured.

meander: One of a series of regular sinuous curves, bends, loops, turns, or windings in the of a,, or other. Meanders are produced by the repetitive upstream erosion and downstream deposition of sediments along the banks of a watercourse as the water flows back and forth across the axis of a or.

meander cutoff: The process by which the separating the two closest parts of a river or stream  is breached by the river's flow, forming a new, shorter channel that effectively "shortcuts" the loop of the meander and causes it to be gradually abandoned until it is completely isolated from the main flow. The river's course suddenly becomes much straighter, and the abandoned meander often forms a or an, or becomes loaded with sediment and dries up entirely, leaving  of the former channel.

meander neck: The narrow strip of land separating the river on each side of a well-developed. If this strip is completely eroded away, a occurs. See also.

meander scar:

A typically crescent-shaped incision in a or valley wall formed by the remnants of a dry, abandoned.

MEDC: An acronym for More Economically Developed Country.

medial moraine:

The debris lying centrally in a line across the surface of a, formed when the of two  glaciers meet.

median line:

medical geography: A branch of that studies the geographical aspects of health and the provision of healthcare, examining the spatial distribution of human diseases, mortality, morbidity, and the environmental factors conducive to human health and illness.

Mediterranean climate: Any climate characterized by mild, rainy winters and hot, dry summers, as experienced in the Mediterranean Basin.

megacity: A very large, typically with a population of at least 10 million people. Precise definitions vary, but criteria are usually based on total population and/or population density.

megafan: An exceptionally large, variously defined as being more than 100 km long from apex to toe or having a surface area of more than 10000 sqkm.

megalopolis: A chain of roughly adjacent which have merged into a very large and heavily populated. See also ' and '.

megaregion:

meilograph: See.

meltwater:

Water (usually ) derived from the melting of snow or ice, including seasonal snowfall, ice,, and over the ocean.

mental map:

Mercator projection:

A  in which the  is represented by a straight line true to scale and  are represented by parallel straight lines perpendicular to the equator and uniformly spaced according to the distances between them at the equator. are also represented by a system of straight lines which are perpendicular to all of the meridians and therefore parallel to the equator, though their spacing is not uniform but rather increases with increasing distance from the equator in order to conform with the expanding scale resulting from the parallel representations of the meridians. The standard Mercator projection has long been popular in because it represents north as up and south as down everywhere in the world while preserving local directions and shapes, though it also greatly inflates the size of objects near the geographic poles.

mere: A shallow,, or. The term is used primarily in Great Britain and other parts of Western Europe.

mereing: A type of in which boundaries are established with respect to ground features present at the time of the survey, which may include natural features and may or may not remain unchanged over time, e.g. a survey.

meridian: A line of, i.e. any imaginary line connecting points of equal longitude and running perpendicular to all, intersecting them at right angles. Unlike lines of latitude, meridians are all the same length, but are not parallel to each other, instead converging at the. Each meridian is half of a drawn on the Earth's surface; the other half, connecting all of the meridian's, is termed an. Meridians are numbered according to their longitudinal measure in angular (further subdivided into  and ) up to 180 degrees east or west of an arbitrarily designated zero or, by convention the.

meridional: Of, relating to, or characteristic of the south, especially of the inhabitants of a southern region or territory, in particular southern Europe. Contrast.

mesa: An isolated, relatively flat-topped natural elevation, usually more extensive than a and less extensive than a.

metamorphic rock: Rock that has been physically altered by heat and/or pressure.

metes and bounds: A system of that defines parcels of land according to visible natural landscape features and distance. The resultant field pattern is usually very irregular in shape.

metropole: The homeland or central territory from which a colonial empire governs, as opposed to its or overseas territories.

metropolis: A large or which is considered a significant economic, political, or cultural center for a  or geographic region and/or an important hub for regional or international connections and communications.

metropolitan area:

A region consisting of one or more densely populated cores (often a ) and its less populous surrounding territories, including satellite,, and intervening areas, all of which are socioeconomically tied to the core as typically measured by commuting patterns. A metropolitan area usually comprises multiple, , and , with its inhabitants sharing industry, housing, and many other forms of infrastructure.

metropolitan coalescence: The merging of the urbanized parts of separate ; a is a result of this process.

metropolitan state:

mire: See.

mogote: An isolated, rounded, steep-sided composed of either limestone, marble, or dolomite and surrounded by nearly flat, especially as found in regions.

Mohorovičić discontinuity: The boundary between the Earth's and the, as defined by the abrupt change in velocity of seismic P waves traveling across this boundary, which occurs as the waves pass through different densities of rock.

mole: A long, massive, man-made stone or earthen structure used as a or, or as a between places separated by water, but designed to prevent the free movement of water underneath it (unlike a true pier).

monadnock: See.

montane: Of or pertaining to a or mountains; mountainous; occurring at high. The term is used in particular to describe or ecological communities occupying cool, humid zones at or near. See also.

monticule: A secondary on the side of a larger, or any small mountain or large hill.

moor:

An upland habitat and characterized by low-growing vegetation on acidic soils and generally referring to uncultivated but also including low-lying.

moraine: The rocks and soil carried and deposited by a. A, either a ridge or low hill running perpendicular to the direction of ice movement, is often visible near the end of a retreating glacier, indicating the glacier's maximum advance.

moulin: A vertical, cylindrical shaft, up to 25 – deep, by which surface flows into a, usually formed at lines of structural weakness in the ice.

mound: Any heaped pile of earth, gravel, sand, rocks, or debris, typically with a rounded top and of topographically higher than its immediate surroundings.

mountain: A large that rises prominently above the surrounding land in a limited area, usually in the form of a rocky peak with great vertical ; a mountain is generally considered steeper than a. Mountains are formed by or  forces and erode slowly through the actions of rivers, glaciers, and. Most exist within extensive.

mountain pass: A navigable route through a or over a, often crossing a.

mountain range: A series of neighboring or, often closely arranged in a line and connected by high ground. Individual mountains within the same mountain range are usually the result of the same, and often (though not always) share a common form, alignment, and geology.

mouth: The place where a or flows into another body of water, such as a  or another river but especially a  or. and occur near the mouths of rivers. The lower or downstream end or the most accessible entrance of a,, , or.

mudflat:

A type of coastal consisting of exposed layers of bay mud formed by the deposition of silts, clays, and marine animal detritus by or. Mudflats usually form within the of relatively sheltered areas such as  and.

mudflow:

A flowing mixture of water and debris (intermediate between a and a water flood) that forms on the slopes of a.

multilingual: The ability to use more than one language when speaking or writing. This term often refers to the presence of more than two populations of significant size within a single political unit, each group speaking a different language as their primary language.

municipal corporation: The legal term for a government body at the local level, including but not necessarily limited to,, , , , and.

municipality: A type of general-purpose having  status and powers of self-government or  as granted by national and/or state laws to which it is subordinate. Municipalities are often included within but usually distinguished from larger administrative divisions such as, though the nature of their territorial boundaries and political jurisdictions can vary considerably in different parts of the world.

muskeg: Another name for a, used primarily in Alaska and western Canada.