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


absolute location
The particular location of a point on Earth's surface that can be expressed by a grid reference such as latitude and longitude.[1]
A locational characteristic that permits a place to be reached by the efforts of those at other places.[2]
accessibility resource
A naturally emergent landscape form that eases communication between areas.[2]
See summit.
active volcano
A volcano that is currently erupting, or one that has erupted within the last 10,000 years (the Holocene) or during recorded history.[3]
The sunny, warm aspect of a hill or mountain, as opposed to the ubac or shady side.[4]
See tributary.
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 primary sector activities.
alluvial fan
A distinctly triangular or fan-shaped deposit of sediment transported by water, often referred to as alluvium. Alluvial fans usually form at the base of mountains, 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 plain created by the long-term deposition of alluvium from one or more rivers flowing from highland regions, and typically characterized by various fluvial landforms such as braided streams, terraces, and meanders. Alluvial plains encompass the larger area over which a river's floodplain has shifted through geological time.
alluvial soils
Soils deposited through the action of moving water. These soils lack horizons and are usually highly fertile.[2]
Clay, silt, gravel, or similar detrital material deposited by flowing water.[2]
Characteristic of or resembling the European Alps, or any other high-elevation mountain range or mountainous environment (especially one deeply modified by glacial erosion so as to contain characteristic landforms such as cirques, horns, etc.), in topography, climate, or ecological communities.[5]
The height of an object in the atmosphere above sea level. Compare elevation.[1]
amphidromic point

Also amphidrome and tidal node.

A geographical location where there is little or no tide, i.e. where the tidal amplitude is zero or nearly zero because the height of sea level does not differ significantly at high tide and low tide, 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 open ocean near the center of the basin, depend largely on the surrounding topography and bathymetry, 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.[6][7]
anastomosing stream

Also anastomosed stream.

A stream or river composed of multiple, branching, interconnected, coexisting channels that enclose floodbasins on alluvial plains, usually formed when a slow-moving river encounters avulsions that divert its flow, creating new channels on the floodplain.[8]

Also anoecumene.

The part of the Earth's surface which is uninhabited and/or uninhabitable by human beings.[4] Contrast ecumene.
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.[4]
The region of the Earth that is south of the Antarctic Circle.
Antarctic Circle
The southernmost of the Earth's two polar circles of latitude, south of which the sun appears above the horizon 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 Equator. Contrast Arctic Circle.
antecedent stream

Also antecedent river and antecedent drainage.

A stream or other watercourse 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 topography. For example, a landscape featuring a river with a dendritic drainage pattern may be altered by gradual, localized tectonic uplift, but the river may be sufficiently powerful to erode through the new obstructions as rapidly as they are formed, carving a gorge 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.[4] Compare insequent stream.
The conversion of open spaces, landscapes, and natural environments by human action.
1.  Of or relating to anthropogeny, the scientific study of the origins of human beings.
2.  Having an origin in human activity; caused by or attributable to humans.[4]
anti-dip stream
A stream flowing in a direction approximately opposite to that of the dip of the underlying surface rocks. It is frequently, though not necessarily, an obsequent stream.[4]
A geological upfold that has an arch-like convex shape and its oldest beds near its center, often visible at the Earth's surface in exposed rock strata. Contrast syncline.
1.  The meridian of longitude that is directly opposite or antipodal 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 great circle that passes through the geographic poles.
2.  The 180th meridian in particular, i.e. the meridian of longitude that is exactly 180 degrees both east and west of the Prime Meridian, with which it forms a great circle dividing the Earth into the Eastern and Western Hemispheres. The 180th meridian is used as the approximate basis for the International Date Line because it mostly passes through the open waters of the Pacific Ocean.
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 great-circle distance between them being approximately 20,000 kilometres (12,000 mi).
anywhere fix
A geographic position which a GPS receiver is able to calculate without requiring information about its own location or the local time.[9]
apogean tide
The tide 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 tidal range than is usual, i.e. lower high tides and higher low tides.[4] Contrast perigean tide.
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 local to global, in disciplines such as civic planning, land use and management, location policy, and population studies, among many others.[4]
apposed glacier
A glacier resulting from the merging of two separate glaciers.[4]
A spread of alluvium deposited by streams, especially those originating from a melting glacier.[4] See also alluvial fan and outwash plain.
A normally permeable rock, underlying or overlying an aquifer, which becomes impermeable because of the saturation of its pores by water, potentially creating a confined aquifer.[4]

Also aquafer.

An underground layer of water-bearing permeable 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 spring, or may be extracted using man-made wells. There are many different types of aquifer with various levels of hydraulic conductivity.[4]
Diagram of multiple aquifers at various depths, showing the water table (dashed line), confining layers, directions of water flow, and groundwater recharge times
Diagram of multiple aquifers at various depths, showing the water table (dashed line), confining layers, directions of water flow, and groundwater recharge times
An impermeable rock stratum which not only obstructs the passage of water but cannot absorb it, e.g. granite.[4]
A bed or layer of rock that slows the conveyance of water from an aquifer due to its low permeability or low hydraulic conductivity.
A collection of islands in a sea.
A sharp, narrow mountain ridge, often resulting from the erosive activity of alpine glaciers flowing in adjacent valleys.[2]

Also wash.

A deep gully cut by a stream that flows only part of the year; a dry gulch. The term is used primarily in desert areas in North America and South America.[2]
The region of the Earth that is north of the Arctic Circle.
Arctic Circle
The northernmost of the Earth's two polar circles of latitude, north of which the sun appears above the horizon 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 Equator. Contrast Antarctic Circle.
Fragments of lava or rock less than 13 centimetre (0.13 in) in diameter that have been ejected into the atmosphere by a volcanic explosion.[3]

Also exposure.

The direction toward which a slope faces with respect to a compass or to the Sun's position in the sky,[5] or the direction which a segment of coastline faces as it meets the sea.
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 waterfalls that occur as the water flows from the hard rocks of the higher piedmont onto the softer rocks of the coastal plain.[2]
Atlantic-type coastline
See discordant coastline.
A bound collection of maps.[1]
The mixture of gases, aerosols, solid particles, and water vapor that envelops the Earth.[3]
A ring-shaped coral reef that partially or completely encircles a lagoon.
autonomous height
See topographic prominence.
A vertical or inclined shaft connecting a cave passage to the surface.[4]
1.  The sudden loss of land by the action of water.
2.  The rapid abandonment by a river or stream of an existing channel 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 activity space, and it enlarges as new locations are discovered and new information is gathered.[4] See also search space and mental map.
1.  (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.
2.  (of a fold) The imaginary central line or plane dividing the limbs of the fold as symmetrically as possible; the crest from which strata dip downward and away in an anticline, or the lowest depth of the trough from which strata rise in opposite directions in a syncline.[4]
3.  (of the Earth) The rotational axis of the Earth: the diameter between the North Geographic Pole and the South Geographic Pole, 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.
Another name for a shingle beach or other gravel-covered spit, bar, or tombolo, used primarily in the archipelagos of northern Scotland.
The angle formed between a reference vector (often magnetic north) and a line from the observer to a point of interest projected perpendicularly to the zenith on the same plane as the reference vector. Azimuth is usually measured in degrees and can be determined with a compass.
azimuthal projection
A map projection in which all bearings 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.[4]


Any geographical area that is remote, isolated, undeveloped, or difficult to access, as contrasted with frontcountry; sparsely populated or uninhabited wilderness. See also bush.
The part of a seashore lying inland from the mean high water line, landwards of the foreshore, from which it is often delineated by the presence of a strandline.[4] This part of the beach is only affected by waves during exceptional high tides or severe storms.
The part of the profile of a hillslope that forms the steepest, typically linear portion of the slope, generally located in the middle and bounded by a convex shoulder above and a concave footslope below. The backslope may or may not include vertical or near-vertical cliffs.[5]
The seaward return flow of a receding wave after it has broken on a beach or other surface.[4] Contrast swash.
1.  A part of a river in which there is little or no current, especially a side channel, a sluggish meander, or a slowing and widening of the main stem created by an obstruction to flow.
2.  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.
3.  A secluded, peaceful place.
In the Middle East, an arid area characterized by low or irregular precipitation and little or no vegetation.[4]
An area of rugged or irregular topography resulting from extensive wind and water erosion of unconsolidated sedimentary rock.[2]

Also bahada.

A series of adjacent alluvial fans coalescing in a basin at the foot of a mountain range.
The political fragmentation of a larger region or state 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.
1.  The land alongside a body of water, particularly the sloping ground bordering and defining the channel of a flowing watercourse such as a river or stream.
2.  An elevation in the bed of a river, stream, or shallow sea, either fully or partially submerged, mid-channel or connected to the shore, and usually made of sand, mud, gravel, or other loose sediment. See also bar and shoal.
3.  Another name for a hill or hillside.
bankfull stage
The stage during which the channel of a river or stream is completely filled with water from bank to bank, immediately preceding the overbank stage, when the river overflows its banks and inundates the surrounding floodplain.[4]
An elevated area of unconsolidated sediment such as sand or gravel which has been deposited by the flow of a river or other moving body of water. See also shoal.
An impoundment built for seasonal floodwater storage and/or to create a reservoir for irrigation, as opposed to a dam, which instead serves the purpose of hydroelectric power generation, though at the broadest level the terms may be used more or less interchangeably.
barrier island
A long, narrow ridge or shoal lying above the highest high tide level (thereby creating an island) and parallel to the mainland coast, from which it is separated by a lagoon.[4] 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 dredging. Though their size and shape change frequently, particularly during storms, they are important natural breakwaters which shelter areas of relatively calm waters where wetlands and marine life flourish. See also spit and tied island.
Diagram of various coastal landforms depicting a barrier island
Diagram of various coastal landforms depicting a barrier island
barrier reef
A coral reef lying parallel to a shore and some distance from it, creating a sheltered lagoon which the reef protects from the open ocean.[4]
barrier ridge
Any steep, unnavigable ridge or escarpment isolating one terrain from another.
In the Spanish-speaking world, a neighborhood or community within a larger urban area, generally with informal boundaries, though in some places the term may refer to a formal subdivision of a municipality.
See tumulus.
The Earth's core and mantle considered together, i.e. all of the Earth's interior beneath the lithosphere.[4]
base level
The lowest level to which a stream can erode its bed. The ultimate base level of all streams is the sea.[2]
An accurately measured line of known length on the Earth's surface, used as a base or reference line in triangulation and other surveying operations.[4]
Another name for a depression, particularly one that is approximately circular, level or nearly level at the bottom, and/or surrounded on all sides by land of uniform elevation.
A very large body of igneous rock, usually granite, which has been exposed by erosion of the overlying rock.[2]
1.  The measurement of water depth, mainly of seas and oceans but sometimes of deep lakes.
2.  The study and depiction of the physical features or relief of the floor of a lake or ocean. In this sense bathymetry is considered the underwater equivalent of hypsometry or topography.
A coastal body of water that is directly connected to but recessed from a larger body of water, such as an ocean, sea, lake, or another bay. The land surrounding a bay usually shelters it from strong winds and waves, making bays ideal places for ports and harbors.
In the southern United States, a sluggish or stagnant slough or backwater, or a marshy outlet of a lake or river.[4]
A landform along the shoreline of an ocean, sea, lake, or river with a loose surface of sand, gravel, shingle, pebbles, shells, stones, or coral.
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 degrees and can be determined with a compass. By convention, magnetic north is defined as having a bearing of zero degrees.
The solid rock in the Earth's crust that underlies all soil and other loose material; the rock material that breaks down eventually to form soil.[2]

Also corridor.

A large region or district (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 (green belt), language or ethnicity (Hindi Belt), or social/cultural demographics (Bible Belt).[4] See also regionalism.
A narrow step, shelf, ledge, or terrace, typically backed by a steep slope, produced either naturally (e.g. by erosion, as with a wave-cut bench) or artificially (e.g. by mining).[4]
A surveying 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 datum level has been accurately measured.
A traditional benchmark of the British Ordnance Survey, consisting of a chiseled arrow indicating a horizontal line (top), and a modern bronze disc benchmark of the United States Coast & Geodetic Survey (bottom)
1.  A mountain or hill; a cliff face or precipice.
2.  Another name for a bergschrund, iceberg, or inselberg.

Also rimaye or simply berg or schrund.

A crevasse or series of parallel crevasses that opens in a glacier when a mass of moving ice detaches and pulls away from stagnant ice or firn. Bergschrunds are common in mountainous areas, often forming seasonally near the back of a cirque where the ice meets a steep or rocky headwall. When the rift forms directly between ice and rock, the gap is called a randkluft.[4]
1.  A level space, shelf, or raised barrier separating two areas, often man-made and built of compacted earth. Berms often function as impoundments, fortification lines, or border walls and other lines of demarcation.
2.  A low, impermanent, nearly horizontal or landward-sloping shelf, bench, or narrow terrace on the backshore of a beach and parallel to the shoreline, formed by waves which deposit material beyond the average high water mark, e.g. during storms. Some beaches have no berms; others may have one or more.[5]
A bend or curve in a coastline, river, or other geographical feature typically indicating an especially large, open bay that is shallower than a sound.
In Australia, a branch of a river that is cut off when the main stem changes course, leaving an elongated and often ephemeral waterhole or oxbow lake.[4]
biological diversity

Also biodiversity.

A concept recognizing the variety of life forms in an area of the Earth and the ecological interdependence of these life forms.[2]
The study of the distribution of biological species and ecosystems in geographic space and through geological time.
The outer part of the lithosphere, from the surface of the Earth to the greatest depth at which organic life can exist.[4]
The entirety of all biological systems on Earth, integrating all living beings and ecosystems; the realm in which biological organisms live.[3]
The animal and plant life of a region considered as a total ecological entity.[2]
The water of a slow-moving river channel flowing through a forested swamp or wetland, characterized by high concentrations of tannins leached from decaying vegetation, which results in a darkly stained color and high acidity.

Also marine geyser.

A hole or fissure, especially a nearly vertical one, that is the landward opening of a sea cave, frequently spouting or spraying air and seawater as waves crash against the cave's other opening.[4]
A sandy depression formed when wind erodes into patches of bare sand on otherwise vegetation-stabilized sand dunes at the margins of coastal and arid ecosystems.
A steep slope or cliff marking the outer margin of a floodplain, especially one formed as the river erodes the concave bend of a meander. See also cut bank.
A landscape of mixed woodland and pasture, with fields and winding country lanes sunken between low, narrow ridges and banks surmounted by tall, thick hedgerows, 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 lakes and oceans, or they may collect and move water from one place to another, as with rivers, streams, and other watercourses.

Also mire, quagmire, or muskeg.

A type of wetland 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.
See salient.
The geographical boundary of a political entity or legal jurisdiction, such as a country, state, or other subnational entity.[1]
1.  (tidal) A steep-fronted wave formed by the convergence of two tidal bulges or by the constriction of an incoming tide as it travels up a river, firth, or narrow bay, temporarily reversing the direction of the current.[4]
2.  (hole) A deep, man-made hole or shaft drilled into the ground, e.g. in mining, or for digging a well or tunnel.
A bald, steep-sided, dome-shaped hill, mountain, or rock outcropping at least 30 metres (98 ft) in height and several hundred meters in width. Compare inselberg, tor, and nubbin.
A type of administrative subdivision in certain English-speaking parts of the world. Though traditionally used to refer to a fortress or a walled town, 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 metropolis (as in New York City and London), or an entire administrative region (as in the U.S. state of Alaska).
See floodplain.
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.[4]
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 border separating political or administrative divisions, zones of occupation, natural areas, or private and public property.[4] See also frontier.

Also bourn, born, borne, and burn.

1.  A seasonal or intermittent stream flowing from a spring in an otherwise dry valley, and whose flow depends on the level of the water table. The term is used primarily in the chalklands of southern England.[4] See also winterbourne.
2.  The spring or fount itself.
box canyon
A short, narrow canyon with steep walls on three sides, allowing entry and exit only through the mouth of the canyon.
See canebrake.
brash ice
See drift ice.
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.
1.  Any more or less abrupt change in the profile of a slope, e.g. of a hillside.
2.  A heavily eroded area along a river featuring steep banks, bluffs, ravines, or gorges. The term is used chiefly in the plural (i.e. breaks) and primarily in the United States and Canada.
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.[2]
Any man-made structure built on the coast of a body of water, typically the sea, 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 longshore drift.
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.[4]
Low-lying, woody, often dense vegetation or plant debris, e.g. scrub; 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.
A type of administrative subdivision in Scotland and northern England, equivalent to a borough.
In parts of the United Kingdom, Australia, and New Zealand, a large stream or a small river. See also bourne.
Wild, undeveloped, or uncultivated land, especially when covered by thick shrubs and vegetation; sparsely populated or uninhabited wilderness. See also backcountry, hinterland, outback, and bushveld.

Also lowveld, or simply bush or veld.

In southern Africa, a tropical or subtropical woodland ecoregion consisting largely of open savanna with scattered trees; wild countryside as opposed to cultivated land.[4]
An isolated hill or mountain with steep or precipitous sides, usually having a smaller summit area than a mesa.[2]
1.  A route 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.[4]
2.  See flood bypass.



Also cadaster.

A type of parcel-based land recording system containing a comprehensive record of interests in individual units of land within a country or other polity, usually including a geometric description of each parcel's physical location, dimensions, and boundaries 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.
A man-made stack or mound of rocks, stones, or masonry, usually roughly conical or pyramidal in shape, constructed as a burial mound, to mark a surveyed point, or as a landmark or waypoint to aid routefinding on a route that is otherwise unmarked and difficult to distinguish from the surrounding environment.[10]
A narrow, steep-sided valley surrounding an inlet formed in karstic regions along the Mediterranean coast, either by fluvial erosion or the collapse of the roof of a cave that has been subsequently partially submerged by a rise in sea level.
A large, cauldron-shaped depression that forms through the subsidence and collapse of a ground surface following the evacuation of an underlying magma chamber.
1.  In the Spanish-speaking world, the rural countryside or the bush.
2.  In Brazil, an area of level, open grassland with scattered trees, comparable to a savanna.[4]
A navigable artificial water channel, usually built as a conduit for human activity.

Also canebreak.

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

Also gorge or cañon.

A deep cleft between cliffs or escarpments, or a rift between two mountain peaks, resulting from weathering and the erosive activity of a river over long periods of geologic time.
A large headland or promontory extending into a body of water, usually a sea or ocean.
capillary fringe
The soil layer lying immediately above the water table, in which water is drawn up and held within pore spaces by capillarity.[4]
1.  A primary city or town 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.[4] A polity may have one or more capitals, or none.
2.  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".
A stratum of erosion-resistant sedimentary rock (usually limestone) found in arid areas. Caprock forms the top layer of most mesas and buttes.[2]
cardinal directions
The set of four primary directions used in cartography and navigation: north (N), south (S), east (E), and west (W). Together they form the primary divisions of the compass rose. They can be further subdivided into the intercardinal directions and secondary-intercardinal directions.
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.[2]
The study and practice of making maps and charts. A person who draws or makes maps or charts is called a cartographer.[1]
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.
A decorative panel or emblem on a map or a globe, enclosing the title, legend, scale, or any other information.[10]
castle koppie
See tor.
A large waterfall, or a long series of rapids in a river, of the type occurring in the river Nile.[4]
See drainage basin.
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 bridge.
Any naturally hollow underground space large enough for a person to enter.
A type of solutional cave that is formed in soluble rock with the ability to grow speleothems.

Also key.

A small, sandy, low-elevation island on the surface of an otherwise submerged coral reef; a type of coral island. Compare atoll.
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 North Pole and South Pole, respectively), and all other points appear to rotate around them.
A natural pit or sinkhole resulting from the collapse of limestone bedrock which exposes groundwater 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 district in an urban area, typically containing a concentration of office and retail activities.[2]
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 geographical center of a region of the Earth's surface is the centroid of the two-dimensional shape of that region, as projected radially to sea level or onto a geoid.[10]
A unit of length equal to 66 feet (20.117 m), used especially in public land surveys in the United States; 10 square chains is equal to 1 acre (0.40 hectares). 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".[11]

Also strait.

1.  A waterway separating two relatively close landmasses.
2.  Any narrow body of water that connects two larger bodies of water.
3.  The deepest part of a shallow body of water, often used as a passageway for large ships.
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.[2]
A special-purpose map designed for navigation, especially nautical and aeronautical navigation, or to present specific data or technical information.[11]
See salient.
A steep-sided coastal gorge, typically of soft eroding cliffs of sandstone or clay, through which a river or stream flows to the sea. The term is used primarily in southern England.
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 (36 °F) in a quarter of an hour.[2]
The art of establishing, describing, or mapping a geographic region or district, or more broadly, the representation of space or place.
The study of the causal relations of the phenomena present in a region; a comprehensive explanatory study of a region.[4]
A map 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.[12]

Also shott and shatt.

An ephemeral, often highly saline lake that forms seasonally with fluctuations in the water table, usually in the winter, in the desert basins of Northwest Africa.[13]
cinder cone
A steep-sided volcano formed by the explosive eruption of cinders that form around a vent. Cinders are lava fragments about 1 centimetre (0.39 in) in diameter.[3]
circle of latitude
See parallel.

Also corrie or cwm.

An amphitheatre-shaped valley surrounded on three or more sides by steep, cliff-like slopes and formed by glacial or fluvial erosion.
A large human settlement, generally with extensive systems constructed for housing, transportation, sanitation, utilities, and communication.
city center
A sovereign state or small independent country that usually consists of a single city and its dependent territories.
1.  The practice of permanently removing vegetation, especially trees and bushes, from a forest or woodland in order to use the space for another purpose, such as agriculture, civic development, or paths for roads, railways, or power lines.
2.  Another name for a glade.
Any vertical or nearly vertical rock exposure, usually formed by the processes of weathering and erosion.
cliffed coast

Also abrasion coast.

A coastline where the repeated action of ocean waves has formed steep and often precipitous cliffs, as opposed to a flat or gently sloping alluvial coast.
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.[2]
See inclinometer.

Also coastline or seashore.

The area where land meets a sea or ocean. Coastal zones are regions where the interaction of terrestrial and marine processes occurs. Compare shore.
coastal bench
See wave-cut platform.

Also gap or notch.

The lowest point on a mountain ridge between two peaks.
The complementary angle of a given latitude; i.e. the arithmetic difference between 90 degrees and the given latitude. For example, the colatitude of 36° 22′ 49″ is 53° 37′ 11″.[4]
A territory under the immediate complete political control of a sovereign metropolitan state but otherwise distinct, often geographically, from the state's home territory. Colonies have no international representation independent of the metropolitan state. Compare satellite state.
Loose, unconsolidated sediment that has been transported and deposited at the base of a hillslope by any of various wash or mass movement processes, such as surface runoff, sheet erosion, or landslides. Typically a heterogeneous mixture of rock types and sizes ranging from silt to talus boulders, colluvium is often derived from eluvium, and differs from alluvium, which is deposited primarily by fluvial activity.[13]

Variously comb, coomb, coombe, and cumb.

A steep, narrow valley or a large hollow on the side of a hill or coastline, especially one enclosed on all but one side. The term is used primarily in southern England, where it often implies a dry ravine in a limestone or chalk escarpment. See also cwm.
An instrument used for navigation and orientation that indicates direction relative to the geographic cardinal directions by measuring the orientation of the Earth's magnetic field with respect to the North Magnetic Pole. Compasses often display markings for angles or degrees, which allow them to show azimuths and bearings, in addition to a compass rose.
compass rose

Also compass star, wind rose, or rose of the winds.

A figure on a compass, map, nautical chart, or monument used to display the orientation of the four cardinal directions — North, East, South, and West — and their intermediate points.
The place at which two or more rivers or other watercourses flow together to form one larger river or watercourse.[2]
Bearing cones; from the conifer family.[2]
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.
One of several very large, contiguous landmasses into which the Earth's land area is divided, generally by geographical or political convention rather than any strict criteria.[1] Geologically, continents correspond largely to areas of continental crust on continental plates.
continental climate
The type of climate found in the interior of the major continents in the middle or temperate latitudes. The climate is characterized by a great seasonal variation in temperatures, four distinct seasons, and a relatively small annual precipitation.[2]
continental divide
The line of high ground that separates the different oceanic drainage basins of a particular continent. The river systems of a continent on opposite sides of a continental divide flow toward different oceans. See drainage divide.[2]
continental shelf
A portion of a continent 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 ocean, they are not part of the deep ocean basin proper but the flooded margins of the continent.
The quality of being located on a continent.
contour line

Also isoline or isopleth.

A line marked on a topographic map which connects points of equal elevation above or below a specified reference datum. Multiple contour lines, each representing a different elevation, are depicted together to show the shape of the terrain within the map area.[3]
contour interval
The difference in elevation between any two adjacent contour lines as depicted on a particular topographic map.[11]
An extensive urban area formed when two or more initially separate cities coalesce to form a continuous metropolitan area.[2]
A long chain of mountain ranges or highlands, especially those formed by the same orogeny and spanning the length of a continent along tectonic 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 hearth.[2]
An accumulation of ice and wind-blown snow overhanging the edge of a ridge or cliff face, usually on the lee side of a steep mountain.[4]
The process of mechanical erosion 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 tarn.
Occurring worldwide; belonging to all parts of the world and free of geographical or political limitations.[4] See also global.
A dry canyon eroded by Pleistocene floods that cut into the lava beds of the Columbia Plateau in the western United States.[2]
A narrow gully with a steep gradient in a mountainous terrain, often enclosed by sheer cliffs and filled with snow or ice even during the summer months.
A region identified as a distinct national entity in political geography. Compare state.
A type of subnational division of a country or federal state used for administrative or other purposes.
The cardinal direction in which a vessel or aircraft is moving, or in which it is steered. This is not necessarily the same as the heading, 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 bearing.
1.  A walled, rounded, cirque-like opening at the head of a small valley.
2.  A small, narrow, sheltered bay, inlet, tidal creek, or recess in an estuary, often within a larger embayment.
3.  A small, often approximately circular, wave-cut indentation or recess in a cliff on a large body of water, especially one with a relatively narrow or secluded entrance.
4.  A shallow tidal river, or the backwater near the mouth of a tidal river.
Any large, roughly circular depression, pit, or hole in the Earth's surface. Craters can be classified into different types based on their ultimate causes; see impact crater, volcanic crater, and pit crater.[3]
crater lake
A lake that forms in a volcanic crater or caldera (such as a maar), an impact crater left by a meteorite, or a crater resulting from a man-made explosion.
An old and stable region of continental lithosphere, characterized by a thick crust composed of ancient crystalline basement rock. Cratons are generally found in the interiors of tectonic plates, having remained relatively unaffected by orogenic and tectonic activity for very long periods of time.[4]
A small, intermittent stream that is larger than a brook but smaller than a river. The term is used primarily in the United States, Canada, and Australia.[5]
1.  A deep crack, fissure, or chasm in the ice of a glacier or ice sheet, or more generally in any ground surface.
2.  A break in the natural levee or bank of a river.[4]
The thin shell of solid material that is the Earth's outermost layer and the outermost component of the lithosphere. The Earth's crust is generally divided into two distinct types, oceanic crust and continental crust, both of which "float" on top of the mantle.[3]
The totality of water in the solid phase on the Earth's surface, including glaciers; sea, lake, and river ice; snow; and permafrost. The cryosphere is sometimes considered a subset of the hydrosphere.[3]

Also frost churning.

The mixing of materials from various horizons of the soil down to the bedrock due to freezing and thawing.
A long, low ridge with a steep scarp slope and a gentle backslope (dip slope).
cultural geography
A branch of human geography which studies the patterns and interactions of human culture in relation to the natural environment and the human organization of space.
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.[2]
culture hearth
The area from which the culture of a group diffused. See also hearth.[2]
A tunnel or conduit that channels water through or beneath an obstacle (e.g. through a man-made crossing of a ravine that would otherwise block the natural flow of water), or any artificially buried watercourse.
See opisometer.
An arc-shaped, dune-like mound of sediment on a beach or foreshore.[13] 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 eroding bank along a meandering river or stream channel, especially a bank that has been eroded into a nearly vertical cliff. Cut banks generally form on the outside bend of a deep meander, opposite the depositional point bar that forms on the inside bend.
The new channel formed when a meandering stream erodes through a narrow strip of land and thereby shortens the length of the main channel.[5]
See cirque.
Cyclopean stairs
A term referring to the longitudinal profile of some glaciated valleys which have been eroded into a series of consecutive hanging valleys resembling stairs.


Another name for a valley.

Also impoundment.

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 levees are more specifically designed to manage or prevent water flow into particular areas).
dasymetric map
A type of thematic map that uses areal symbols to visualize a spatially dependent variable (e.g. population density) by refining a choropleth map 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 isarithmic maps, combining their strengths and weaknesses in order to more accurately depict quantities that vary continuously across space.[4]
datum plane

Also datum level or datum line.

The zero-elevation baseline or vertical datum to which a measurement of elevation or altitude is relative, e.g. the mean sea level calculated for a given location over a given period of time.[4] See also geodetic datum.
de facto segregation
The spatial and social separation of populations that occurs without legal sanction.[2]
de jure segregation
The spatial and social separation of populations that occurs because of legal measures.[2]

Also debouche.

A place where water runoff from a relatively small, confined space emerges into a much larger, broader space, or where a body of water 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.[2]
A trough-like depression or trench in the ocean floor, of limited extent but great depth, generally more than 5,500 metres (18,000 ft) below sea level.[4]
deferred junction
A narrow pass or gorge between mountains or hills.
A unit of angular measure, represented by the º symbol. A circle is divided into 360 degrees; subdivisions of the degree include the minute (160 of one degree) and the second (13600 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 latitudes and longitudes.[1]
degree day
Deviation of one-degree temperature for one day from an arbitrary standard, usually the long-term average temperature for a place.[2]
A small, secluded hollow, usually within a grassy, park-like, partially wooded valley.
A landform at the mouth of a river where the main stem splits up into several distributaries. It is formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Compare estuary.[5]
The study and systematic analysis of population, particularly human population.[2]
A pillar of rock weathered from volcanic breccia or similar material and capped by a large boulder which has protected the material underneath.[4]
The uncovering of deeper layers of rock by any natural process, e.g. erosion, weathering, or mass movement.[4]

Also dependent territory.

A territory relying on or subject to the control of another country, neither possessing full political independence nor forming an integral part of the controlling country's political or economic interests.
Any natural process by which material such as soil and rocks is added to a landform or landmass, e.g. by the action of wind, water, ice, or gravity in transporting previously weathered surface material, which comes to rest when sufficient kinetic energy is lost and accumulates in layers of sediment. See also sedimentation.
Any landform 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 erosion, ground collapse, tectonic activity, volcanism, and meteorite impacts.
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.[4] See also brownfield land.
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 denudation 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 desertification, or by their geographical location.
desert pavement

Also reg, serir, gibber, saï, and desert mosaic.

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.[4]
desert varnish

Also desert patina, rock varnish, and rock rust.

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.[4]
The process by which a previously fertile area becomes increasingly arid, infertile, or desert-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 map 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.[4]
desire path

Also social trail.

Any path or trail, often a footpath, created as a consequence of erosion caused by human or animal traffic, usually representing the shortest or easiest route 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 pond built to capture and hold rainwater or sea mist in order to water livestock, made especially in areas where natural supplies of surface water are not readily available, such as on the chalk downlands of southern England.[4]
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 terrain surface created from elevation data. DEMs are the most common basis for digitally produced relief maps.
1.  A ditch, wall, embankment, or ridge, natural or man-made, that is an obstacle to something else; another name for a levee.
2.  In geology, an intrusion in which molten rock has ascended through an approximately vertical fissure and solidified into a wall of rock that is often harder or less permeable than the rocks of the surrounding strata.[4]
A type of administrative division used by certain Christian churches for religious purposes.
In hydrology, 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 stream channel) 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

Also Atlantic-type coastline.

A coastline which cuts transversely across the predominant orientation of the local geological strata, i.e. not parallel to them, as with a concordant coastline.[4]
dissected plateau
A landscape produced by significant stream erosion and incision of a plateau 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 hills or badlands.[5]
distance decay
The decrease in cultural or spatial interactions between two places as the distance between them increases. This effect may be noticeable in towns and cities, where certain characteristics such as pedestrian traffic, building height, and land value tend to decline with greater distance from the city center.
A stream or river that branches off and flows away from a main channel and does not return to it. Distributaries are common near river deltas. Contrast tributary.
A type of administrative subdivision 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 municipal or county 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.
See drainage divide.
In parts of South Asia, the low alluvial plain lying between and reaching to the confluence of two rivers or streams.[13] See also interfluve.

Also vrtače and shakehole.

A shallow enclosed basin or funnel-shaped depression typical of karst landscapes, usually with a flat floor and linked to the underlying drainage system by a vertical shaft.[4] See also sinkhole.
1.  A steep-sided mound that forms when very viscous lava is extruded from a volcanic vent.[3]
2.  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.[2]
In southern Africa, another name for a gully or badland carved by extreme erosion.[13]
dormant volcano
An active volcano that is in repose (quiescence) but is expected to erupt in the future.[3]
dormitory town
See commuter town.

Also down and downs.

An open, treeless expanse of gently undulating, elevated grassland, usually of chalk and supporting grazing for livestock. The term is used primarily in southern England, Australia, and New Zealand.[4]
In English-speaking North America, the commercial, cultural, and often historical and/or geographical center of a city or town, especially a large city within a major metropolitan area, often synonymous with its central business district.
The natural or artificial removal of surface and/or sub-surface water from an area with excess water, e.g. via runoff facilitated by channels such as streams and rivers, into which water collects and is transported to sea level by gravity. The patterns, hierarchies, and evolution of drainage networks are widely studied in physical geography disciplines.
drainage basin

Also catchment, drainage area, river basin, water basin, or watershed.

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

Also ridgeline, watershed, water parting, water divide, or simply divide.

The topographical barrier that separates neighboring drainage basins. Divides are often, though not always, located along conspicuous elevated ridges or mountain ranges.

Also re-entrant.

1.  A terrain feature formed by two parallel ridges or spurs with low ground in between them.
2.  Another name for an arroyo, ravine, or gulch, especially one with a broad floor and gently sloping sides.[5]
draw down
The maximum extent to which the water table is reduced in elevation as a result of pumping water from a well that penetrates an aquifer. The amount of draw down diminishes logarithmically with distance from the site of the well, a fact which determines the shape of the subsurface cone of depression in the area surrounding the well.[13]
drift ice

Also brash ice.

A type of sea ice consisting of multiple ice floes that are not attached to the shoreline or any other fixed object such as a shoal, and which are therefore free to "drift" under the influence of winds and ocean currents. Contrast fast ice.
drowned valley
A valley which was originally formed on land but later partially or entirely submerged beneath the sea due to a rise in sea level. See also fjord, calanque, and ria.
An elongated hill in the shape of an inverted spoon or half-buried egg which is formed by glacial ice acting on underlying unconsolidated till or ground moraine.
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.[2]
dry gap
See wind gap.
dry point
An area of firm or dry ground in a wetland, marsh, or floodplain, often capable of supporting a human settlement.
An ecoregion 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 savannas to hyper-arid extremes such as deserts.
A hill of loose sand built by the movements and erosional and depositional processes of wind or water, often occurring in deserts and coastal areas.


Earth science

Also called the Earth sciences or geoscience.

1.  A collective term for the various fields of natural science related to the planet Earth.
2.  The branch of science that studies the physical constitution and characteristics of the Earth and its atmosphere, using methods and tools from geography, geology, physics, chemistry, biology, and mathematics to build a quantitative understanding of how the Earth works and changes over time.
A sudden and intense shaking of the ground due to tectonic activity.
Eastern Hemisphere
The half sphere of the Earth that is east of the Prime Meridian and west of the antimeridian. It is opposite the Western Hemisphere.
economic distance
The physical distance a commodity may travel before its value is exceeded by the costs of transporting it.[4]
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.[2]

Also called an ecological region.

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

Also oecumene.

1.  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.[4]
2.  All of human civilization considered collectively.
edge city
A concentration of businesses, commercial buildings, or retail and entertainment venues situated outside of a traditional downtown or central business district in what was previously a suburban residential or rural area.
The transitional areas of "fringe" space at the boundaries of a country, city, 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 hinterland.
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.[4]
The scientific study of human settlements 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 human geography concerned with analysis of the organization, methods, results, and consequences of political elections in the context of geographic space and using geographical techniques.
1.  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 sea level (or at least to a reference geoid used as an approximation of the Earth's mean sea level). Compare altitude, geopotential height, and depth.[1]
2.  The vertical angle between the horizontal and a high point, e.g. between the horizon and a star in the night sky, or between the base of a mountain and its summit.[4]
3.  In architecture, a view of one of the sides of a building, or a drawing of this view.[4]
See reference ellipsoid.
1.  The rise of the level of a land surface with respect to the sea, so that land formerly under the sea becomes dry.[4]
2.  The location at which an underground stream or aquifer comes to the surface.[4]
emergent coastline
A coast or shoreline resulting from a rise in land surface elevation relative to sea level.[2]
To reclaim by the creation of a polder.[4]
A tract or territory completely surrounded by and enclosed within the territory of exactly one other state, country, or other political entity. Unlike enclaves, exclaves can be surrounded by more than one other state.[2]
The independent country of Lesotho is completely enclaved by the country of South Africa. The country of Eswatini, to the east, is not an enclave because it borders two countries: South Africa and Mozambique.
The independent country of Lesotho is completely enclaved by the country of South Africa. The country of Eswatini, to the east, is not an enclave because it borders two countries: South Africa and Mozambique.
Restricted or exclusive to a certain place, region, or people, having originated there, and existing nowhere else.[4]
endorheic basin

Also endoreic basin, closed basin, or terminal basin.

A closed drainage basin that allows little or no outflow to external bodies of water but converges instead into internal lakes or swamps which equilibrate through evaporation.
Embedded within a glacier. Contrast subglacial and superglacial.

Also entrepot or transshipment port.

A place (e.g. a port, 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.[4] 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.
The area surrounding a particular geographical place, i.e. its surroundings or environment.
The point on the Earth's surface directly above the focus of an earthquake, near which the seismic waves produced by the earthquake are usually most noticeable.
equal-area projection
The imaginary great circle around the Earth halfway between the geographic poles which is assigned a latitude of zero degrees and therefore used as a reference point for all other lines of latitude. It is the largest circumference of the Earth.[1]
equirectangular projection

Also reg and hamada.

A broad, flat desert area covered by wind-swept sand and having little or no vegetative cover.
A boulder that has been carried from its source by a glacier and deposited as the glacier melted. Such boulders are often conspicuous because they differ geologically from the surrounding rock.[2]
A long cliff or steep slope separating two comparatively level or more gently sloping surfaces and resulting from erosion or faulting.[2]

Also called an os or spelled eskar or eschar.

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

Also inversac.

A karstic sinkhole or ponor which, depending on the season and weather conditions, can serve as either a sink or a source of freshwater.
The broad lower course of a river where it enters the ocean and is affected by the tides. Compare delta.[2]
A shallow pool or lake caused by the ponding of backwash draining from a beach by material brought ashore by the sea.[4]
A plain beneath which the bedrock has been subjected to considerable subsurface weathering, known as "etching". Erosion of the regolith overlying an etchplain often exposes topographical irregularities such as inselbergs.
See pothole.
See plucking.
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 enclaves.
exotic stream
A stream found in an area that is too dry to have spawned such a flow. The flow originates in some moister section.[2]
extinct volcano
A volcano that is not expected to erupt again.[3]
An adjective describing a region or district that lies outside a city and usually beyond its suburbs; a place of this type is called an exurb. Compare rural.[2]


fall line
A geomorphologic unconformity between an upland region of relatively hard crystalline basement rock and a coastal plain of softer sedimentary rock.
Agricultural land that is plowed or tilled but left unseeded during a growing season. Fallowing is usually done to conserve moisture and soil nutrients.[2]
false origin
A selected point in a projected coordinate system 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 true origin in order to exclude negative values.[4]
fast ice
A fracture in the Earth's crust accompanied by a displacement of one side of the fracture.[2]
fault-block mountain
A mountain mass created by either the uplift of land between faults or the subsidence of land outside the faults.[2]
fault zone
An area of numerous fractures 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.[2]
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.[2]
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 surface or groundwater 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 bogs. Fens are one of four main types of wetland, along with bogs, marshes and swamps.
1.  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 sightlines.
2.  (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 GIS 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 geodesy. 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 geoids.
A type of ice that is at an intermediate stage between snow and glacial ice. More specifically, firn is partially compacted névé 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 floodplain that experiences regular flooding, i.e. the first part to be inundated when a flood occurs, though the frequency considered "regular" is inconsistently specified. The term is used primarily in the Midwestern United States.
First Law of Geography

Also Tobler's First Law of Geography.

A fundamental assumption of spatial analysis 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 spatial dependence and autocorrelation,[9] and is expressed mathematically in the inverse distance weighting method of spatial interpolation and in regionalized variable theory as the basis for kriging.
Another name for a coastal inlet, strait, or bay associated with the mouth of a large river, where the tidal effects of seawater passing upriver have widened the riverbed into an estuary. 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 dams as they swim upstream to spawn.[2]
A long, narrow opening or line of breakage made by cracking or splitting, especially in rock or earth.[2]

Also fiord.

A long, narrow marine inlet with steep sides or cliffs created by glacial erosion.
flood bypass
flood wall
A primarily vertical artificial barrier designed to temporarily contain the waters of a river or other waterway which may rise to high levels during flooding events. Flood walls are narrower and typically easier to build than dikes or levees, so they are mainly used in locations where space is limited or where building more traditional flood-control structures would interfere with other interests.
See levee.

Also bottomland.

A broad, flat area of land adjacent to a river or stream which is leveled by annual flooding and by the lateral and downstream movement of meanders.
1.  Another name for a flood bypass.
2.  A large-capacity channel or culvert 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 levees. They often run below street level in larger cities.
3.  A road crossing of a flood-prone channel, built at or close to the natural ground level. It is similar to a causeway but crosses a shallow and often dry depression that is subject to flooding, rather than a continuously flooded waterway.
4.  A part of a floodplain kept clear of encumbrances and reserved for emergency diversion of floodwaters.
The level or nearly level lower part of a valley or basin, or the bed of any body of water, such as a stream, lake, or ocean.
A glacial landform created by the movement of a glacier around a boulder, consisting of a lineation or streamlined furrow or ridge parallel to the direction of ice movement. They generally form in newly deposited till or older drift and can reach heights of 25 metres (82 ft) and lengths of 20 kilometres (12 mi).
Of or pertaining to rivers or streams; produced by the action of a river or stream.[5]
fluvial terrace
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.

Also hypocenter.

The point inside the Earth's crust from which an earthquake originates.
A geographic transition zone defined by gradual increases in elevation between plains or low-relief hills and adjacent topographically higher hills, mountains, or uplands.
The part of the profile of a hillslope 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 shoulder and backslope) and sites of deposition further down the slope (the toeslope).[5]
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 bridge). Fords may be seasonal or temporary, becoming impassable during high water.
A relatively narrow, deep, elongated, and steep-sided trough in the ocean floor, usually near or parallel to a mountainous land area or associated with an archipelago, or such a trough when infilled with sediment.[4] See also foreland basin.
1.  Any land area or territory located in front of something else.
2.  A landform projecting into the sea, e.g. a cape or headland.
3.  The seaward trading area associated with a particular port or harbor.[4]
4.  (glaciology) The area between the current leading edge of a glacier and the moraines of the most recent maximum.
foreland basin
A type of structural endmember basin that develops adjacent and parallel to a mountain range 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 rift basin.
The part of a seashore located between the lowest low water line and the mean high water line.[4] See also intertidal zone; contrast backshore.
Any extensive area dominated by communities of trees.
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 salt water or brackish water. Sources of fresh water on Earth include glaciers, ice caps, icebergs, bogs, lakes, rivers, streams, and most groundwater.
functional diversity
The characteristic of a place where a variety of different activities (economic, political, or social) occur, most often associated with urban places.[2]


A geographical dictionary or directory used in conjunction with a map or atlas and containing information concerning the geographical make-up, social statistics, and physical features of a country, region, or continent.

Also geodetics.

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

Also geodetic network, reference network, or control point network.

geodetic datum

Also geodetic system, geodetic reference datum, or geodetic reference system.

A coordinate system and set of reference points used for locating places on the Earth, which defines horizontal and vertical coordinates upon a particular reference ellipsoid that approximates the figure of the Earth. Geodetic datums are used in geodesy, navigation, and surveying applications to translate positions indicated on paper or digital maps 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 World Geodetic System.
geodetic north
See true north.
See geodesy.
A subfield of geophysics and Earth science 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 plate tectonics and geological phenomena such as mountain formation, volcanism, earthquakes, and faulting, among others.
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 elevation and two or three other numbers represent a horizontal position such as latitude and longitude.
geographic information science (GIS)

Also GIScience.

The scientific study of data structures and computational techniques for capturing, representing, processing, and analyzing geographic information.
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 data.
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 record identifier called a GNIS identifier.
geographical inertia

Also geographical momentum.

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.[4]
geographical mile
A unit of length defined as the distance equal to one minute of arc along the Earth's Equator: approximately 1,855.3 metres (1.1528 mi; 1.8553 km). The precise length varies with the reference ellipsoid used to approximate the shape of the Earth. Regardless of the particular ellipsoid, the length of one degree of longitude at the Equator is equal to exactly 60 geographical miles.
The scientific study of the lands, features, inhabitants, and phenomena of Earth.
The shape that the surface of the Earth's oceans would take under the influence of Earth's gravity and rotational acceleration alone, in the absence of other influences such as winds and tides. It is often characterized as the precise mathematical figure of the Earth: 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 spirit levels 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 reference ellipsoid is an idealized approximation of the more complex and accurate geoid.
The science and technology which develops and uses information science infrastructures to address problems and analyze data within geography, cartography, geoscience, and related branches of science and engineering.
The identification or estimation of the real-world geographic location of an object, involving the generation of a set of geographic coordinates in order to determine a more meaningful description of location, such as a street address.

Also geospatial science.

The scientific discipline that involves gathering, storing, processing, and delivering geographic or spatially referenced information.
The study of the arrangement and form of the Earth's crust and of the relationship between these physical features and the geologic structures beneath.[2]
See Earth science.
The study of geographical knowledge from any and all points of view, past or present, true or false;[14] the study of the nature and expression of geographical ideas.[4]
geospatial science
See geomatics.
The collective non-living parts of the Earth: the lithosphere, the atmosphere, the cryosphere, and the hydrosphere.[3]
A branch of statistics which involves the organization, management, and analysis of spatial and spatiotemporal datasets. Geostatistical algorithms are often incorporated in GIS software applications.
See physical geography.
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.[2]
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 drift
See drift.
glacial flour
See rock flour.
glacial lake
A lake or other enclosed body of water created by historical or ongoing glacial activity; e.g. the Great Lakes of North America.
glacial till
The mass of rocks and finely ground material carried by a glacier and deposited when the ice melts. This creates an unstratified material of varying composition.[2]
glacial trough
1.  The process or state of being covered with a glacier.
2.  Another name for a glacial period, an interval of time that is marked by colder temperatures and advancing glaciers.[2]
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 cirques, moraines, and fjords. They form exclusively on land and are distinct from the much thinner ice that forms on bodies of water.[3]

Also clearing.

Any large, open, mostly treeless area within a forest.
A long valley bounded by gently sloping, concave sides, and typically narrower and deeper than a strath. The term is used primarily in Scotland.
A steep cliff, terrace, or edge of a plateau.[4]
1.  Of or concerning all parts of the world (i.e. worldwide); affecting or distributed across the whole of the Earth.
2.  Of or relating to a globe or sphere; spherical.
3.  Comprehensive; total; encompassing all or nearly all considerations, categories, items, etc.[4]
global city

Also world city, power city, or alpha city.

A city 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 Positioning System (GPS)
A satellite-based radionavigation positioning system 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 GNSS standards that provides geolocation and time information, transmitted via microwave signals, to enabled satellite navigation devices, 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 centimetres (0.98 ft).
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.
A true-to-scale map of the Earth that duplicates its round shape and correctly represents relative areas, sizes, and shapes of physical features, distances, and directions.[1]
See panhole.
1.  An irregularly shaped parcel of land of any size, often approximately triangular, that is left between two adjoining surveyed parcels as the result of incomplete or inaccurate boundary surveys.[15]
2.  A lune-shaped map which may be fitted to the surface of a globe with a negligible amount of distortion.[15]
See canyon.
A depression or valley bounded on either side by distinct, parallel escarpments or faults and formed by the downward displacement of a block of the Earth's crust. Grabens often occur side-by-side with horsts, their uplifted or non-displaced counterparts, in a repeated series of vertical displacements.

Also slope, incline, gradient, pitch, rise, or mainfall.

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 hills or mountains or the beds and banks of watercourses.
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 biome occurring worldwide, grasslands may be natural or created for agricultural purposes.
A network of lines on a map or chart (or imagined on the surface of the Earth) representing geodetic parallels of latitude and meridians of longitude.[10]
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

Also orthodrome.

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 as each other, which by definition is the largest possible circumference of the sphere. The mathematical properties of great circles make them useful in geodesy, where they are often visualized upon the surface of the Earth (despite the fact that the Earth is not a perfect sphere): for example, the Equator of the idealized Earth is a great circle, and any meridian with its antimeridian 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, great-circle distances are often used as approximations of geodesics for the purposes of air and sea navigation.
great-circle bearing
The horizontal direction or bearing followed by the arc of a great circle through a given pair of terrestrial points, expressed as the angular distance from a reference direction.[15]
great-circle distance

Also orthodromic distance.

The length of a line between two points which follows the arc of a great circle 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.[2]
green belt

Also greenway.

A special land-use zone designated in some cities to prevent development of wild, largely undeveloped, or agricultural land surrounding or adjacent to urban areas, in order to conserve natural ecosystems, to allow the return and establishment of wildlife, and/or to create urban green space 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.
A pattern of lines on a chart or map, such as those representing latitude and longitude, which helps determine absolute location.[1]
grid magnetic angle

Also grid variation or grivation.

The angular difference in direction between grid north and magnetic north, typically expressed in degrees east or west of grid north.[15]
grid north
The direction northwards as indicated by the grid lines of a map projection, which may or may not be aligned with geodetic north and magnetic north.
See grid magnetic angle.
The water present beneath the Earth's surface in soil pore spaces and in fractures and voids within geological strata. Contrast surface water.
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 Northern Hemisphere, this typically occurs in the spring) to the average date of the first frost (in the autumn).[2]
A rigid, man-made hydraulic structure extending from an ocean shore or river bank, constructed to interrupt water flow and limit the movement of sediment by longshore drift.
A deep, V-shaped valley formed by erosion, often containing a small stream or a dry streambed, especially one in arid regions.
A large arm or inlet of an ocean or sea that lies within a curved coastline, similar to a bay but usually larger and often with a narrower opening.
A landform resembling a large ditch or a small ravine created by the action of swift running water eroding deeply and sharply into soil, typically on a hillside.
Any very fine, clayey soil which rapidly turns to sticky mud when wet. The term is used primarily in the United States and Canada.[13]

Also tablemount.

An isolated underwater seamount with a flat top that is at least 200 metres (660 ft) below the water's surface.
Any large system of circulating ocean currents, particularly those related to large-scale wind movements. Gyres are caused by the Coriolis effect and play a fundamental role in the global thermohaline circulation.
The Earth's oceans circulate within five major gyres – the North Pacific, North Atlantic, South Pacific, South Atlantic, and Indian Ocean Gyres – as well as many smaller accessory currents, depicted here on a map projection with a south polar aspect.
The Earth's oceans circulate within five major gyres – the North Pacific, North Atlantic, South Pacific, South Atlantic, and Indian Ocean Gyres – as well as many smaller accessory currents, depicted here on a map projection with a south polar aspect.
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 attitude and/or course of a moving object such as an airborne or waterborne vehicle or camera. Modern digital gyroscopes and their associated supporting readouts are widely used in navigation and geodesy as the basic sensor in direction-seeking, direction-keeping, and attitude stabilization systems.[15]


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.[4]
Any of a series of non-numerical lines used on a map to indicate the general orientation and steepness of topographical terrain. Such lines vary in length, thickness, and spacing, with steeper slopes indicated by shorter, heavier, and more closely spaced lines.[11]
A coastal lagoon of fresh or brackish water on the south coast of the Baltic Sea, fed by a stream which is blocked by a nehrung, through which it is linked to the sea by a channel.[4]
halo effect
In the context of geography, the detrimental effect of a border 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.[4]
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 homestead to a town.[4]

Also hammada.

A desert landscape consisting of high, largely barren, rocky plateaus where most of the sand has been removed by deflation, and thus lacking most surficial materials other than boulders and exposed bedrock.[13]
A small human settlement, variably defined as one the size of a town, village, or parish or as a smaller subdivision of or satellite entity to a larger settlement.
hanging valley
A tributary valley 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 glacial erosion, when adjacent areas beneath a glacier are subjected to different rates of erosion.
harmonic tremor
One of a series of continuous rhythmic earthquakes in the Earth's upper lithosphere that can be detected by seismographs. Harmonic tremors often precede or accompany volcanic eruptions.[3]
head of navigation
The farthest point above the mouth of a river that can be navigated by watercraft, whether because of natural or man-made obstacles.
The compass direction 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 course; 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 bearing.
A high coastal promontory that extends out into a body of water, often surrounded by steep cliffs. A very large headland is often called a cape.
A steep slope or sheer cliff face at the upper end of a valley (e.g. at the back of a cirque), or at the active face of a mine, pit, or quarry.[5]
1.  Another name for the source of a river, stream, or other watercourse, i.e. the point or points furthest from the mouth of a particular stream, at which precipitation, meltwater, or groundwater first accumulates into a persistent, identifiable, and/or named body of water whose contents ultimately empty into the particular stream; or all of the uppermost streams of a watershed considered collectively (of which there may be thousands), typically including all streams identified as first-order through third-order in conventional stream order systems.
2.  The entire region, inclusive of land, surrounding these sources, often abutting the boundary of a drainage divide that separates different watersheds.
The source area of any innovation. The source area from which an idea, crop, artifact, or good is diffused to other areas.[2]
1.  The central or interior part of a region.
2.  A part of a region considered essential to the viability and survival of the whole.

Also heathland.

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 acres. There are 100 hectares in 1 square kilometre (km2).[4]

Also simply called a hedge.

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.
A device used in geodetic surveying to reflect sunlight onto a distant point so as to aid long-distance observations.[15]
One half of the Earth, usually conceived as resulting from the division of the globe into two equal parts of either north and south or east and west.[1]
heteroclinal fold
A geological fold of which one side is sloped at an angle steeper than that of the other side.[4]
high plain
A plain lying at a high elevation, generally above 600 metres (2,000 ft).[4]
high water mark
A natural or man-made demarcation that indicates the maximum rise of a body of water 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 tidal cycle). A natural delineation created by debris deposited by a high tide is called a strandline. See also wash margin and mean high water.

Sometimes used interchangeably with upland.

1.  Any elevated region of land, often one that is mountainous or situated atop a plateau. The term is sometimes reserved for relatively low-elevation mountain ranges or foothills.
2.  Any area of land (mountainous or otherwise) that is higher in elevation relative to another area. In this sense, the term is often used as a conditional descriptor to distinguish related habitats or ecosystems, especially freshwater riparian areas, on the basis of elevation above sea level.
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 populated places.
Any landform that extends above the surrounding terrain. A hill is generally considered less steep than a mountain.

Also knoll.

A small hill.
1.  An area that is tributary to a place and linked to that place through lines of exchange or interaction.[2]
2.  The area, not necessarily settled itself, that is nonetheless influenced by a particular settlement or establishment, i.e. its sphere of influence.[4]
historical geography
A branch of human geography 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.[4]
A projecting ridge or outcropping of land, its height ending abruptly or steeply. The term is used primarily in placenames in Great Britain.

Also hog's back or hogsback.

A long, narrow ridge or series of hills with a narrow crest and steep, symmetrical slopes of nearly equal inclination on both flanks, especially one created by the differential erosion of an outcropping which exposes homoclinal sedimentary rock strata. Compare esker, drumlin, and cuesta.
Aerial view of a hogback in the southwestern United States
Aerial view of a hogback in the southwestern United States
Land owned or occupied by legal right for the purpose of agriculture.[4]
1.  (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 rural settlement of dispersed farms.[4]
2.  (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 improve it. Homesteaders were initially granted plots of 160 acres (0.65 km2), which was considered adequate to support a single family, but later as much as 640 acres (2.6 km2).

Also skyline.

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 metres (10 ft) from the horizontal, the horizon in any direction is approximately 6.5 kilometres (4 mi) distant; at 30 metres (100 ft), it is 21 kilometres (13 mi) away.[4]
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 map, as opposed to measuring the actual physical length along the real-world surface, which can be greatly increased by slopes 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.[4]
A mountain formed by the back-to-back abutment of three or four adjacent cirques, leaving a distinctly pyramidal peak.[12]
A raised block of the Earth's crust, bounded by parallel escarpments or faults, that has been displaced upward or has remained stationary while adjacent blocks on either side, known as grabens, have been displaced downward. Horsts and grabens often occur side-by-side in a repeated series of vertical displacements.
An area in the middle of a lithospheric plate where magma rises from the mantle and erupts at the Earth's surface. Volcanoes sometimes occur above a hotspot.[3]
A residual hill in limestone country, resembling a haystack, left standing when the surrounding land surface is eroded.[4]
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 physical geography, it is one of the two major sub-fields of geography.
humanistic geography

Also humanist geography.

An approach in human geography 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.[4]
A small knoll or mound, typically less than 15 metres (49 ft) in height and situated above an otherwise level ground surface.
Partially decomposed organic soil material.[2]
In England, Scandinavia, and many other parts of the world, an administrative subdivision of a larger region, often a county or shire, with its own judicial authority.[4]
The study of the surface waters of the Earth.[2]
A graph showing the rate of flow (i.e. the discharge) 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).
The totality of the water found on, under, and above the Earth's surface in liquid, solid, and gaseous forms, including all oceans, lakes, rivers, and streams, as well as all ice and glaciers and subsurface groundwater. Some definitions restrict the hydrosphere to liquid water only, instead placing solid forms in the cryosphere and gaseous forms in the atmosphere.[3]
The geographic representation on a map of features related to elevation, altitude, and other measures of height above a reference surface.
The study or measurement of land elevation relative to mean sea level. Hypsometry is the terrestrial equivalent of bathymetry.


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 polar ice sheets and widespread glaciation. The most recent such period was the Pleistocene Epoch, which ended approximately 12,000 years ago.[2]
ice cap
A flattened, often dome-shaped mass of ice that covers less than 50,000 square kilometres (19,000 sq mi) of land area and is not constrained by topographical features such as mountains; larger masses of ice are termed ice sheets. Contrast polar ice cap.
ice floe
A large piece of floating drift ice, typically with a flat surface and at least 20 metres (66 ft) across at its widest point.
ice sheet

Also continental glacier.

A mass of glacial ice that covers more than 50,000 square kilometres (19,000 sq mi) of land area; smaller masses of ice may be termed ice caps or ice shelves. The two polar ice sheets are the only ice sheets that currently exist on Earth.
ice shelf
A large floating platform of ice formed when a glacier or ice sheet in a coastal area flows onto the ocean surface. By contrast, sea ice is formed directly over the water and is typically much thinner.
ice stream
A region of relatively fast-moving ice within an ice sheet that flows like a stream under its own weight (making it essentially equivalent to a glacier) and empties into the ocean. Ice streams are responsible for the majority of the mass lost from both the Antarctic and Greenland ice sheets.
A large chunk of fresh water ice which has broken away from a larger body of ice (such as a glacier or ice shelf) and is floating freely in open water.
A portion of a glacier 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 crevasses and seracs.
igneous rock
Rock formed when molten (melted) materials harden.[2]
impact crater
A type of crater formed by the hypervelocity collision of a solid astronomical body, such as a meteor, with the Earth's surface. Unlike volcanic craters, impact craters typically have raised rims higher in elevation and depressed floors lower in elevation than the surrounding terrain.
1.  Another name for a dam that impounds a body of water.
2.  The reservoir 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.[4]

Also clinometer, declinometer, tilt meter, gradient meter, slope gauge, and level gauge.

An instrument used to measure angles of slope, elevation, or depression 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.[13]
index contour
A contour line drawn with a heavier line weight to distinguish it from intermediate contours. Depending on the contour interval, index contours are usually indicated every fourth or fifth contour, along with their assigned numerical values, in order to facilitate ease of interpretation.[15]
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.[2]
The broad set of facilities and interrelated systems that serve a city, country, 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, water reservoirs, canals, 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

Also ingressed coast and depressed coast.

A generally flat coastline 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 crustal movements or a rise in sea level, such that the boundary between land and water closely matches the topographic contours of the land prior to its being covered by seawater.
Of, relating to, within, or towards the interior of a landmass, i.e. distant from the coast.
inland sea
A very large, isolated expanse of open water in the interior of a landmass, either completely surrounded by dry land or connected to the ocean by a river, strait, or other narrow waterway.
An indentation of a shoreline, usually long and narrow, which leads to an enclosed body of salt water, such as a sound, bay, lagoon, or marsh.

Also monadnock.

An isolated rocky hill, knob, ridge, or small mountain that rises abruptly from a virtually level surrounding plain. Compare mogote.
A subsection of a map that is reserved for depicting another map of the same place at a different scale, often a smaller scale to show relative location within a larger geographic area (e.g. a country's location on the globe) or a larger scale to show increased detail (e.g. of public transit routes in a downtown area), 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, graticule, and legend.[16]
(relative to a position on a body of water) Near to or moving towards the shore; shorewards of a position as opposed to seawards of it. See also onshore and offshore.
Of or relating to an island, or suggestive of the isolated condition of an island.[2]
integrated drainage
A drainage pattern in which stream 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 closed drainage systems are present.[5]
integrated geography

Also integrative geography, environmental geography, or human–environment 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

Also intermediate directions or ordinal directions.

The set of four intermediate directions used in cartography and navigation, each of which is located halfway between a pair of cardinal directions: northeast (NE), southeast (SE), southwest (SW), and northwest (NW). They are often included in the compass rose and are used to define further subdivisions such as the secondary-intercardinal directions.
A narrow, elongated, and plateau-like or ridge-like landform between two valleys, or an area of higher ground between two rivers in the same drainage basin.
intermediate directions
See intercardinal directions.

Also intermountain.

Situated between mountains or mountain ranges, e.g. the high plateaus lying between the eastern and western ranges of the Andes.[4]
International Date Line
A line of longitude generally 180 degrees east and west of the Prime Meridian. The date is one day earlier to the east of the line.[1]
international waters
In geographic information science, the estimation of the values of spatially dependent variables 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 kriging are commonly raster operations, but can also be applied in vector environments using a triangulated irregular network to model a surface.[9]
Any place where the contiguous geographic area represented in a map projection 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 world maps, for example, have at least one interruption, conventionally along the length of a single meridian, thus forming an east–west boundary despite that the approximately spherical shape of the Earth 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 gores, each with its own central meridian.[9]
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.[2]
Intracoastal Waterway (ICW)
A system of navigable inland waterway 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 4,800 kilometres (3,000 mi) from Boston, Massachusetts, around the southern tip of Florida, to Brownsville, Texas.[2]
See estavelle.
inverted river delta
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 country or polity whose territory consists primarily or entirely of one or more islands or parts of islands.
A very small island.
Having equal measure.
Any line on a map 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 contour lines) or temperature (as with isotherms), or a quantity related to social or economic statistics, such as population, wealth, or transport costs.

Also isostatic equilibrium.

The state of gravitational equilibrium between the Earth's crust and its mantle, such that the crust "floats" at an elevation that depends on its thickness and density. This concept is invoked to explain how different topographic 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 oceans tend to change over time in order to compensate for the uneven distribution of mass in the lithosphere. For example, the instability of continental margins 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.[4]
A narrow piece of land connecting two larger land areas across an expanse of water by which they are otherwise separated.


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

Also jhoom cultivation or slash-and-burn agriculture.

Clear-cutting and/or setting fire to an area of land so it can be used for farm cultivation.
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.
An area covered with dense vegetation dominated by large trees, often tropical.
1.  The right and power to apply the law in a particular place or within a defined field of responsibility.
2.  The geographical area to which such authority applies.


An irregularly shaped hill or mound composed of sand, gravel, and glacial till which accumulates in a depression on a retreating glacier and is subsequently deposited on the land surface with further melting of the glacier. Kames are often associated with kettles.
Kames and kettles are just two of the many characteristic landforms created in the wake of a melting glacier.
Kames and kettles are just two of the many characteristic landforms created in the wake of a melting glacier.
A furrow or channel varying in depth from a few millimetres to more than a metre, and separated from others by ridges, caused by solution on limestone surfaces.[4]
An area possessing surface topography resulting from the underground solution of subsurface limestone or dolomite.[2]

Also kettle hole or pothole.

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

Also kil.

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

Also nickpoint.

1.  A point of abrupt inflection in the longitudinal profile of a river or its channel or valley, such as occurs at a waterfall.
2.  Any interruption or break in the character of a slope.[5]
A peak or projection from the top of a hill or mountain, or any rounded protrusion of land, especially a small but prominent or isolated hill with steep sides; a boulder or an area of resistant rock protruding from the side of a hill or mountain. The term is used primarily in the southern United States.[5]
See hillock.

Also colc and colk.

1.  A violently rotating underwater vortex capable of plucking and scouring depressions in bedrock, which may leave behind distinct pits or lakes known as rock-cut basins or potholes.
2.  Another name for a bog pond.
See tor.
In Russia and other Slavic countries, a generic term for a region, historically and politically reserved for border regions in particular, and variously translated as march, frontier, or territory. The term is cognate with the name of Ukraine.

Also Gaussian process regression and Wiener–Kolmogorov prediction.

In geostatistics, an interpolation technique in which, for a given spatially dependent variable, 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 GIS applications, kriging is based on regionalized variable theory, which assumes that the spatial variation in the data being modeled is homogeneous across the surface.[9]
A sandy desert of Central Asia, roughly equivalent to the Saharan erg.[4]
In Scotland, a narrow channel or strait between two islands, or between an island and the mainland.[4]


lacustrine plain
A nearly level land area formed by the infilling of a lake with sediment and the complete drainage or evaporation of water from the lake, leaving the deposited sediments behind.[2]
A small area of water connected to the ocean but otherwise blockaded by one or more islands.
See mudflow.
A body of water localized in a basin and surrounded entirely by land. Lakes are often defined as separate from any river 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, tectonic activity, or post-glacial rebound. Compare isthmus.
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-tied island
See tied island.
A natural feature of the solid surface of the Earth. A combined set of landforms makes up the terrain of a given area, and their arrangement in a landscape is known as topography.
Any natural or artificial feature that is recognizable enough to be used for navigation; a feature that stands out enough from its environment to be visible across long distances.
Any large contiguous area of land typically surrounded by an ocean or sea. Compare continent.
1.  A broad or distinct area of land consisting of a collection of landforms which define a general geomorphologic form or setting, e.g. a mountain range, valley, plain, coast, etc. Landforms within a landscape are spatially associated but may vary in formation processes and age.[5]
2.  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; bodies of water such as rivers, lakes, and the sea; living elements of land cover such as vegetation; human elements such as buildings, structures, and various forms of land use; 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.
lateral blast
A sideways-directed explosion from the side or summit of a volcano.[3]
A measure of distance north or south of the Equator. One degree of latitude equals approximately 110 kilometers (68 mi).[2] Lines of latitude, also called circles of latitude 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.[1]
The term used for magma once it has erupted onto the Earth's surface.[3]
A process of soil nutrient removal through the erosive movement and chemical action of water.[2]
The side or slope of a physical feature (such as a hill or mountain) which faces downwind, i.e. away from the direction in which the wind is blowing, or which faces away from an advancing glacier or ice sheet. The lee side is often sheltered by the topography from exposure to the wind and any moisture it brings.[5]
Toward the lee side; sheltered from the wind; the direction downwind from a point of reference. Contrast windward.[3]
A key for understanding the meanings of the symbols or pictures on a map.[1]
An acronym for Less Economically Developed Country.

Also dike, embankment, floodbank, or stopbank.

An elongated naturally occurring ridge 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 river or a coastline.
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 lithospheric plates or tectonic plates.[3]
lithospheric plates

Also tectonic 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 mantle.[3]
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.[12]
A particular point or place in physical space. Compare absolute location.
location theory
A group of theories which seek to explain the siting of economic activities in particular locations.
A soil made up of small particles that were transported by the wind to their present location.[2]
A measure of distance east or west of the Prime Meridian, a line drawn between the North and South Poles and passing through the Royal Observatory at Greenwich, England.[2] Lines of longitude, also called meridians, 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.[1]
longshore drift
Any area of land that is lower in elevation relative to another area. The term is often used as a conditional descriptor to distinguish related habitats or ecosystems, especially freshwater riparian areas, on the basis of elevation above sea level. Lowland areas are usually relatively flat and characterized by slow-flowing waterways and alluvial plains. Contrast upland.


A broad, shallow, flat-bottomed volcanic crater created by an eruption involving groundwater coming into contact with magma. Maars commonly have low rims and subtle relief and characteristically fill with water to form crater lakes.
A fertile, low-lying, grassy plain on the northwest coasts of Ireland and Scotland.
Molten rock containing liquids, crystals, and dissolved gases that forms within the upper part of the Earth's mantle and crust. When erupted onto the Earth's surface, it is called lava.[3]
magmatic water
See juvenile water.
magnetic anomaly
A local deviation from the predicted value of the Earth's magnetic field, 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.[4]
magnetic declination

Also magnetic variation.

The angle on the horizontal plane between magnetic north and true north. Because compass needles always point to magnetic north, and because the Magnetic North Pole and the Geographic North Pole 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 bearing reported by their compass, yielding the true bearing with respect to true north.
magnetic dip

Also dip angle and magnetic inclination.

The angle made with the horizontal by the Earth's magnetic field lines. Locations in the Northern Hemisphere usually have positive values of inclination, indicating that the magnetic field is angled downward, into the Earth; the angle increases as one approaches the North Magnetic Pole, where the field lines point vertically downward, perpendicular to the horizontal. Locations in the Southern Hemisphere usually have negative inclination, indicating that the field lines are angled upward, away from the Earth, with the maximum angle located at the South Magnetic Pole. Dip angle is in principle the angle made by the needle of a vertically held compass, 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 dip circle.
magnetic meridian
magnetic north
The direction a compass points, towards the Magnetic North Pole. Magnetic north differs from true north and grid north.
magnetic pole
Either of the two poles of the Earth's true magnetic field – the Magnetic North Pole or the Magnetic South Pole.
magnetic variation
See magnetic declination.
main stem

Also trunk.

The primary downstream channel of a river, as contrasted with its tributaries. Virtually all of the water in a river's drainage basin eventually flows through the main stem.
See grade.
A term used to denote a contiguous landmass or political territory relative to its politically associated but geographically remote outlying territories. It is variously used to refer to the continental (i.e. non-insular) part of a polity relative to its exclaves or oceanic islands; or to the largest or most politically, economically, and/or demographically significant island within an island nation. 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.
A deep, closed valley (usually drained by a single wadi) surrounded by steep walls of resistant rock and superficially resembling a crater. The term is used primarily in the deserts of Israel and Egypt.
Smooth and rounded in appearance, used of various landforms of different sizes from individual rocks to entire landscapes.[12]
The layer of the Earth's interior between the crust and the core, 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 magma penetrating the crust). The mantle is about 2,900 kilometers (1,800 mi) thick, making up 84% of the Earth's volume and 67% of its mass. The uppermost sub-layer is known as the asthenosphere; the lithosphere is composed of the topmost 65–70 kilometres (40–43 mi) of the mantle and the crust.[3][4]
A picture of a place drawn at an established scale 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 coordinate reference system;[1][15] more generally, any graphical representation of locative information about the relative positions of particular features within a space or place.
map index

Also index map.

A graphical key identifying the relationships between the individual maps of a map series, 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 map sheet which depicts the indicated area in greater detail.[15]
map projection
A systematic transformation of the latitudes and longitudes of locations from the surface of a three-dimensional shape, such as a sphere or an ellipsoid, into locations on a two-dimensional plane. Maps 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 map sheets usually having the same scale and cartographic specifications and collectively identified by the publisher or producing agency as belonging to the same group.[15]
map sheet
An individual map or chart printed on a single page or sheet of paper, either complete in itself or part of a map series.[15]

Also marche or mark; (pl.) marches or marchlands.

A boundary, frontier, or borderland, as opposed to an interior heartland. In medieval Europe, a march was the land surrounding a border between realms, or a neutral buffer zone under the joint control of two or more realms with conflicting laws or territorial claims.[4]
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 improvements 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.
1.  Of, relating to, found in, or produced by the sea or ocean.
2.  Of or relating to shipping or navigation, particularly by watercraft.[4]
maritime climate
A climate strongly influenced by an oceanic environment, typically found on islands and the windward shores of continents. It is characterized by small daily and yearly temperature variation and high relative humidity.[2]
market orientation
The tendency of a firm or industry to be located close to wherever demand for the commodities it produces is strongest.[4]
A type of wetland 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.
1.  Any section of the Earth's crust which is demarcated by faults or flexures and tends to retain its internal structure while being displaced as a whole.
2.  A single large mountain mass or compact group of connected mountains forming an independent portion of a mountain range.
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.[4]
mean sea level (MSL)
The average sea level of one or more of the Earth's coastal bodies of water, such as oceans and seas, from which heights such as elevation and altitude are measured.
One of a series of regular sinuous curves, bends, loops, turns, or windings in the main channel of a river, stream, or other watercourse. 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 valley or floodplain.
meander cutoff
The process by which the strip of land separating the two closest parts of a meandering river or stream channel 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 slackwater or an oxbow lake, or becomes loaded with sediment and dries up entirely, leaving visible traces of the former channel.
A meander cutoff occurs when a river erodes through the neck of a pronounced meander, creating a "shortcut" that isolates the meander loop from the river's main channel.
A meander cutoff occurs when a river erodes through the neck of a pronounced meander, creating a "shortcut" that isolates the meander loop from the river's main channel.
meander neck
The narrow strip of land separating the river on each side of a well-developed meander.[4] If this strip is completely eroded away, a cutoff occurs. See also neck.
meander scar

Also meander scarp.

A typically crescent-shaped incision in a bluff or valley wall formed by the remnants of a dry, abandoned meander.
An acronym for More Economically Developed Country.
medial moraine

Also median moraine.

The morainic debris lying centrally in a line across the surface of a glacier, formed when the lateral moraines of two confluent glaciers meet.[4]
medical geography
A branch of human geography 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.[4]
Mediterranean climate
Any climate characterized by mild, rainy winters and hot, dry summers, as experienced in the Mediterranean Basin.[2]
A very large city, 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.
A chain of roughly adjacent metropolitan areas which have merged into a very large and heavily populated urban complex. See conurbation and metropolitan coalescence.
See opisometer.

Also snowmelt.

Water (usually freshwater) derived from the melting of snow or ice, including seasonal snowfall, glacial ice, icebergs, and ice shelves over the ocean.[4]
mental map
Mercator projection

Also equatorial cylindrical orthomorphic map projection.

A conformal cylindrical map projection in which the equator is represented by a straight line true to scale and meridians are represented by parallel straight lines perpendicular to the equator and uniformly spaced according to the distances between them at the equator. Lines of latitude 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.[15] The standard Mercator projection has long been popular in navigation 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.
A type of surveying 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 metes and bounds survey.[9]
A line of longitude, i.e. any imaginary line connecting points of equal longitude and running perpendicular to all lines of latitude, 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 geographic poles. Each meridian is half of a great circle drawn on the Earth's surface; the other half, connecting all of the meridian's antipodes, is termed an antimeridian. Meridians are numbered according to their longitudinal measure in angular degrees (further subdivided into minutes and seconds) up to 180 degrees east or west of an arbitrarily designated zero or prime meridian, by convention the International Reference Meridian.
Of, relating to, or characteristic of the south, especially of the inhabitants of a southern region or territory, in particular southern Europe.[4] Contrast septentrional.
An isolated, relatively flat-topped natural elevation, usually more extensive than a butte and less extensive than a plateau.[2]
metamorphic rock
Rock that has been physically altered by heat and/or pressure.[2]
metes and bounds
A system of land survey that defines land parcels according to visible natural landscape features and distance. The resultant field pattern is usually very irregular in shape.[2]
The homeland or central territory from which a colonial empire governs, as opposed to its colonies or overseas territories.
A large city or conurbation which is considered a significant economic, political, or cultural center for a country or geographic region and/or an important hub for regional or international connections and communications.
metropolitan area

Also metro area or commuter belt.

A region consisting of one or more densely populated urban cores (often a metropolis) and its less populous surrounding territories, including satellite cities, towns, and intervening rural areas, all of which are socioeconomically tied to the core as typically measured by commuting patterns. A metropolitan area usually comprises multiple neighborhoods, jurisdictions, and municipalities, with its inhabitants sharing industry, housing, and many other forms of infrastructure.
metropolitan coalescence
The merging of the urbanized parts of separate metropolitan areas; a megalopolis is a result of this process.[2]
metropolitan state
See bog.
An isolated, rounded, steep-sided hill composed of either limestone, marble, or dolomite and surrounded by nearly flat alluvial plains, especially as found in tropical regions.
A long, massive, man-made stone or earthen structure used as a pier or breakwater, or as a causeway between places separated by water, but designed to prevent the free movement of water underneath it (unlike a true pier).
See inselberg.

Also moorland.

An upland habitat and ecoregion characterized by low-growing vegetation on acidic soils and generally referring to uncultivated hills but also including low-lying wetlands.
The rocks and soil carried and deposited by a glacier. A terminal moraine, 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.[2]
A vertical, cylindrical shaft, up to 25–30 metres (82–98 ft) deep, by which surface meltwater flows into a glacier, usually formed at lines of structural weakness in the ice.[13]
Any heaped pile of earth, gravel, sand, rocks, or debris, typically with a rounded top and of topographically higher elevation than its immediate surroundings.
A large landform that rises prominently above the surrounding land in a limited area, usually in the form of a rocky peak with great vertical relief; a mountain is generally considered steeper than a hill. Mountains are formed by volcanic or tectonic forces and erode slowly through the actions of rivers, glaciers, and weathering. Most exist within extensive mountain ranges.
mountain pass
A navigable route through a mountain range or over a ridge, often crossing a saddle.
mountain range
A series of neighboring mountains or hills, 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 orogeny, and often (though not always) share a common form, alignment, and geology.
1.  The place where a river or stream flows into another body of water, such as a lake or another river but especially a sea or ocean. Deltas and estuaries occur near the mouths of rivers.
2.  The lower or downstream end or the most accessible entrance of a valley, canyon, ravine, or cave.

Also tidal flat.

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

Also debris flow or lahar.

A flowing mixture of water and debris (intermediate between a volcanic avalanche and a water flood) that forms on the slopes of a volcano.[3]
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.[2]
municipal corporation
The legal term for a government body at the local level, including but not necessarily limited to cities, counties, towns, townships, villages, and boroughs.[17]
A type of general-purpose urban administrative subdivision having corporate status and powers of self-government or jurisdiction 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 counties, though the nature of their territorial boundaries and political jurisdictions can vary considerably in different parts of the world.
Another name for a bog, used primarily in Alaska and western Canada.



Also narrow.

A land or water passage that is confined or restricted by its narrow breadth, often a strait or a water gap.
A stable community of people formed on the basis of a common geographic territory, language, economy, ethnicity, or psychological make-up as manifested in a common culture.
national mapping agency
A governmental agency which manages, produces, and publishes topographic maps, geographic data, and sometimes cadastral information that is specific to an individual nation or political territory, such as the United Kingdom's Ordnance Survey.
national park
A type of protected area created and managed as a public park by a national governmental authority for conservation purposes. Though individual governments designate national parks differently, they usually share the common goal of preserving natural or semi-natural landscapes (often wilderness) for posterity and as symbols of national pride.
natural landscape
The original landscape that exists before it is acted upon by humans. Contrast cultural landscape.
1.  The determination of position and direction, generally by comparing the navigator's position to known locations or patterns.
2.  The process of monitoring and controlling the movement of a vehicle or craft from one place to another.
A line separating the main body of a map from the map's margin. On a standard quadrangle map, the neatlines are the meridians and parallels delimiting the quadrangle.[11]
1.  A narrow stretch of land with water on each side, e.g. an isthmus or promontory.[4]
2.  A narrow stretch of woodland or of ice.[4]
3.  A high level pass, especially the narrowest part.[4]
A long sandspit separating a haff or lagoon from the sea, especially one along the south coast of the Baltic Sea.[4]

Also neighbourhood or abbreviated to hood.

A geographically localized community within a larger city, town, suburb, or rural area, particularly one which supports considerable face-to-face interactions between residents.
In Scotland and parts of England, a headland or cape, or another name for a cuspate foreland; or a spur of a mountain ridge.[4]
nodal region
A region characterized by a set of places connected to another place by lines of communication or movement.[2]
North Geographic Pole

Also called the Geographic North Pole, Geographic North, or simply the North Pole.

The point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is the northernmost point on Earth, directly opposite the South Geographic Pole, and defines the direction of true north at a latitude of 90 degrees North; its longitude can be assigned any degree value. Unlike the South Pole, the North Pole is not located on a continental landmass but in the middle of the Arctic Ocean. See also North Magnetic Pole.
North Geomagnetic Pole

Also called the Geomagnetic North Pole.

The point in the Northern Hemisphere where the axis of a theoretical simplified dipole passing through the center of the Earth would intersect the Earth's surface. It is antipodal to the South Geomagnetic Pole. Because of the fluid nature of the Earth's molten core, the true axis of the Earth's magnetic field is not a perfect dipole, and so the Geomagnetic Poles and the actual Magnetic Poles lie some distance apart.
North Magnetic Pole

Also called the Magnetic North Pole or Magnetic North.

The point in the Northern Hemisphere at which the Earth's magnetic field points vertically downward. It is close to but distinct from the Geographic North Pole and the Geomagnetic North Pole, and its precise location varies considerably over time due to frequent magnetic changes in the Earth's core. Its counterpart in the Southern Hemisphere is the South Magnetic Pole, though the two poles are not directly opposite each other.
Northern Hemisphere
The half sphere of the Earth that is north of the Equator. It is opposite the Southern Hemisphere.
A small, gentle hill consisting of a bedrock core dotted with rounded residual boulders. Nubbins form in a similar way to castle koppies and bornhardts.


A combination of a human settlement and an area of cultivated vegetation in an otherwise desolate desert or semi-desert environment, made fertile when sources of fresh water, such as underground aquifers, irrigate the surface naturally or via man-made wells.
oblate spheroid
The approximate geometric shape of the Earth: a three-dimensional ellipsoid that is nearly but not exactly a true sphere, being instead slightly flattened at the poles and slightly elongated at the equator.
(of a stream, river, or any natural water flow) Flowing in the direction opposite to that of the dip of the underlying rock strata.[4] Contrast consequent and subsequent.
The vast, contiguous body of salt water covering more than 70% of the Earth's surface area and surrounding the continental landmasses; or any portion of this larger body of water that is divided and distinguished from the other portions, each of which is called an ocean, by the presence of the landmasses.[1] The International Hydrographic Organization recognizes five principal oceanic divisions on Earth: from largest to smallest, they are the Pacific Ocean, Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean.
ocean current
ocean floor
See seabed.
ocean trench
A long, narrow, very deep depression in the ocean floor where, at the junction of two tectonic plates, one plate is subducted steeply beneath the other, often penetrating the mantle.

Also oceanology.

The scientific study of the Earth's oceans and all processes and phenomena relating to them, including their formation and evolution over time; their physical and chemical properties and how these vary within the ocean and across its boundaries; their interactions with landmasses along coasts; the bathymetry and geology of the sea floor; currents, waves, and geophysical fluid dynamics; marine life and ecosystems; and how humans affect and are affected by oceans. The interdisciplinary field draws from and involves a diverse range of other sciences, including physics, biology, geology, hydrology, meteorology, and climatology, among others.
See ecumene.
1.  Moving away from the shore and toward the sea.[4]
2.  Located at a point or in an area that is relatively close to but still seaward of the shore (as with an offshore island). Contrast onshore.[4]
3.  Seaward of the foreshore and the backshore.[4]
One of a series of regularly spaced bands of alternating height and color visible on the surface of some glaciers, resulting from seasonal patterns of alimentation and ablation. Because ice flows faster near the center of the glacier, where there is less friction with the surrounding glacial bed, ogives are usually shaped into conspicuous arcs that point towards the terminus of the glacier.[18]
open ocean
The part of the ocean that is beyond or outside of coastal areas,[19] i.e. distant from land and not enclosed or partially enclosed by it. In oceanography, the term is synonymous with pelagic zone and is often defined as all oceanic waters seaward of any continental shelf; politically and economically, "open ocean" usually refers to all areas of a sea or ocean that are not within territorial waters (hence, any area that is within international waters) or, much more restrictively, not within any sovereign state's exclusive economic zone. See also high seas.
open range
A cattle- or sheep-ranching area characterized by a general absence of fences and in which livestock are by law allowed to roam freely.[2]

Also curvimeter, meilograph, or map measurer.

An instrument used to measure the lengths of arbitrary curved lines, especially the distances of rivers and roads on a map.
ordinal directions
See intercardinal directions.
ordnance datum (OD)
Any vertical datum used by the British Ordnance Survey as the basis for reporting elevations on maps. In modern Great Britain, the standard ordnance datum is the ODN, defined as the mean sea level calculated from hourly observations of the tidal gauge at Newlyn, Cornwall, between 1915 and 1921. All heights shown on British maps are measured from this benchmark.[4]
The position of or the act of positioning a person or object with respect to the directional points of a compass, especially the placement of a map or surveying instrument in the field so that a north–south line on the map or instrument lies parallel to a north–south line on the ground.[4] Determining one's orientation at a given time is the chief aim of orienteering, and is generally of critical importance in navigation.
orographic rainfall
Precipitation that results when moist air is lifted over a topographic barrier, such as a mountain range.[2]
A branch of physical geography and geomorphology concerned with the scientific study and description of the topographic relief of the Earth, particularly of mountains and hills, and more broadly of any elevated terrain.[4]
See great circle.
orthodromic distance
See great-circle distance.

Also orthophoto, orthoimage, or orthoimagery.

An aerial photograph or satellite image that has been geometrically corrected or orthorectified such that the scale is uniform across all parts of the image, allowing the image to align with a particular map projection. In an uncorrected aerial photo, distances on the ground may be distorted by topographic relief, camera tilt, or the curvature of the Earth; techniques of digital image processing can compensate for these distortions, often by combining multiple images captured from slightly different perspectives into a single composite image. Orthophotos can be used to measure true distances because they accurately depict the relative sizes and positions of features on the Earth's surface.
In Australia, the vast, remote, sparsely populated backcountry. See also bush.

Also outcropping.

Any visible exposure of bedrock or ancient superficial deposits on the surface of the Earth; or more generally, any bare, rocky surface that is topographically distinct from the surrounding terrain. Outcrops occur frequently in places where the rate of erosion exceeds the rate of weathering, such as on steep hillsides and mountains, river banks, and coastlines.
Rocky and sandy surface material deposited by melted water that flows from a glacier.[2]
outwash plain
1.  Alluvial sediment, usually consisting of fine sand, silt, and clay, that has been deposited on the floodplain of a river or stream by flood waters that have broken through or overtopped the river's banks.
2.  The stage when a river or stream overflows the banks of its normal channel and spreads on to a floodplain, depositing such sediment.
Material covering a mineral seam or bed that must be removed before the mineral can be removed in strip mining.[2]
1.  A wide U-shaped meander in a river or stream.
2.  The lake formed when a meander is cut off from the main stem of the river, creating a separate body of water.


Pacific-type coastline
See concordant coastline.
An uncultivated, treeless grassland in Southeast Asia, sometimes swamp-like, supporting a scrubby heath-type vegetation common on leached sandy soils.[4]
1.  A wall of wooden stakes used as a defensive barrier.
2.  A line of bold cliffs, especially one showing basaltic columns.[2]

(pl.) palsen

An elliptical dome-like permafrost mound containing alternating layers of ice lenses and peat or mineral soil, commonly 3–10 metres (10–33 ft) high and 2–25 metres (7–82 ft) long, and occurring frequently in bogs in the Arctic and subarctic zones of discontinuous permafrost.[5]

(pl.) pampas

In parts of South America, a vast, fertile, grassy plain; or the temperate lowland region encompassing these plains.
Any shallow, generally rounded basin or hollow, which may seasonally capture and hold water from rainfall or snowmelt, especially one occurring in an arid or semi-arid region; more specifically, the flat central part of such a depression, which may be temporarily or seasonally flooded.[4]
See salient.

Also gnamma, weathering pit, and solution pan.

A rounded or circular depression eroded into flat or gently sloping cohesive rock, typically shallow and ranging in diameter from a few centimeters to several meters, that is capable of collecting and holding rainwater and snowmelt. The term is sometimes used interchangeably with pothole, though the latter may also refer to distinct geological features.
In southern Brazil, a wetland region consisting of a usually dry savanna that is seasonally flooded by a river.[4]
An instrument that enables the mechanical copying of a map or technical drawing on a selectable scale, such that the movement of one pen, in tracing an image, produces identical movements in a second pen, resulting in a duplicate image that is the same size, enlarged, or miniaturized with respect to the original. Pantographs typically consist of hinged rods arranged in the shape of a parallelogram which rotate about a fixed point.[4]
1.  (geometry) Extending in the same direction, equidistant at all points, and never converging or diverging; having the same orientation, nature, tendency, or course; corresponding or similar.
2.  (geography) Another name for a circle of latitude.
A type of subnational division of a country or federal state used for religious, administrative, or other purposes.
See mountain pass.
passive glacier
A glacier with low rates of both alimentation and ablation because it receives only light snowfall and undergoes little melting throughout the year. Such glaciers move very slowly and transport relatively small amounts of ice and debris.[4] Contrast active glacier.
Any land used for grazing by livestock, often a natural grassland supporting native grasses and forbs with little or no active management by humans, as opposed to a meadow, where the vegetation is mown for hay or silage.[4]
1.  A pointed or protruding top or vertical projection on a landform, e.g. a mountain, especially implying the highest point or elevational maximum, i.e. the summit.[4]
2.  A mountain as a whole, in particular a high, isolated, or prominent one.
An eroded, often bare rock platform, cut into the local bedrock, usually slightly concave and triangular in shape and extending over a considerable area at the foot of an abrupt mountain slope or face, the lower edge sloping gently away. Pediments form basal slopes of transport for weathered material derived from the steeper slope above, and are characteristic of arid and semi-arid lands.[4]
The scientific study of the morphology, composition, and spatial distribution of soils, with an emphasis on classifying soils and understanding their formation and evolution.[4]
pelagic zone
A piece of land surrounded by water along the majority of its border while still being connected to a mainland from which it projects.
perched water table
perennial stream
A stream that normally flows continuously throughout the entire year, without drying up, as opposed to a transient or intermittent stream.
1.  Of or relating to an area located adjacent to or on the margin of an ice sheet or glacier, either presently or in the past; or to associated phenomena.[4]
2.  Any place where seasonal cycles of freezing and thawing modify the landscape in a significant manner.

Also periplous.

A historical manuscript listing the ports, safe anchorages, and coastal landmarks that a maritime vessel could expect to encounter along a shore or coastline, arranged in order according to a particular direction of travel and including the intervening distances between them. See also itinerarium.
A permanently frozen layer of soil;[2] permanently frozen ground at high latitude and high elevation.[3]
petrographic province
photic zone

Also euphotic zone, epipelagic zone, and sunlight zone.

The uppermost layer of a body of water (e.g. a lake or ocean), defined by the maximum depth to which sunlight can penetrate the water column. The photic zone usually supports large populations of photosynthetic organisms and the majority of the aquatic life inhabiting the body as a whole.
1.  The science and technology of obtaining reliable information about physical objects and environments through the process of recording, measuring, and interpreting photographic images (usually aerial or orbital ones) and patterns of electromagnetic radiant imagery and other phenomena.
2.  The science of extracting three-dimensional measurements from two-dimensional data, such as images.
phreatic water
See groundwater.
phreatic zone

Also zone of saturation.

The part of an aquifer that is below the water table, where nearly all pores and fractures are fully saturated with water. Contrast vadose zone.
physical geography

Also physiography or geosystems.

The branch of geography that studies processes and patterns in the natural environment, such as the atmosphere, hydrosphere, geosphere, and biosphere, as opposed to the cultural or built environment. Along with human geography, it is one of the two major sub-fields of geography.
physiographic region
A portion of the Earth's surface with a common topography and morphology.[2]
Another name for physical geography.[2]

Also foothills.

Any geographic region lying or formed at the base of mountains. The term is used primarily in the southeastern United States to refer to a broad region extending from the Blue Ridge Mountains to the Atlantic coastal plain.[2]
piezometric surface

Also potentiometric surface.

A periglacial landform consisting of a relatively large conical mound of soil-covered ice, commonly 30–50 metres (100–160 ft) high and up to 1,000 metres (0.6 mi) in diameter, and that grows and persists in part as a result of hydrostatic pressure within and below the permafrost of Arctic and subarctic regions.[5]
pit crater

Also subsidence crater or collapse crater.

A type of crater formed by the sinking or collapse of the surface lying above a void or empty chamber. Pit craters are similar to calderas and are often associated with volcanic activity, but lack the ejecta deposits and lava flows of volcanic craters.
place identity
place utility
The measure of approval or satisfaction accorded by an individual to a location in his or her action space; the value or usefulness of a particular place as perceived by a particular person. Dissatisfaction with place utility may result in migration.[4]
See toponym.
1.  (mineral deposit) An accumulation of valuable minerals, particularly gold, formed by gravity separation from a source rock during natural sedimentary processes. The minerals, weathered from rocks or veins, are washed out by streams and mixed with alluvial deposits of sand or gravel, from which they can then be extracted by placer mining.
2.  (reef) A flat, shallow sandbank or reef submerged beneath the ocean surface, often with a sandy bottom suitable as an anchorage for seagoing vessels.
Any broad, flat expanse of land that generally does not show significant variation in topography or elevation.
plane table

Also plain table.

A small drawing board mounted on a tripod used in surveying, site mapping, and related disciplines to provide a solid and level surface upon which to make drawings, charts, and maps while in the field.
planimetric map
A map which uses a two-dimensional coordinate system, i.e. in which each point is represented by only two coordinates (x, y), as if all of the depicted features existed within a single, flat plane. These maps usually exclude information about vertical position and therefore do not show topographic relief and represent only horizontal distances.[9]
A cadastral map, drawn to scale, showing the legal boundaries and divisions of a surveyed tract of land, particularly of the type used to divide real property for sale and settlement in the Public Land Survey System of the United States.[9]
plate tectonics
A geologic theory that the bending (folding) and breaking (faulting) of the solid surface of the Earth results from the slow movement of large sections of that surface called plates.[2]

Also high plain or tableland.

A large area of relatively flat terrain that is significantly higher in elevation than the surrounding landscape, often with one or more sides with steep slopes.
platted land
Land that has been divided into surveyed lots.[2]
An exceptionally flat, arid basin that is the dry bed of an evaporated lake; or the shallow, usually saline lake itself which periodically forms when the basin is temporarily covered with water, e.g. after substantial rainfall. See also salt pan.

Also exaration.

An erosional phenomenon whereby a glacier gradually scours and displaces pieces of rock from the bedrock beneath it and transports them along with the glacial flow of ice and debris. As the glacier moves down a valley, friction causes the basal ice to melt and infiltrate joints and cracks in the bedrock; repeated freezing and thawing widens and deepens these cracks, eventually loosening the rock and causing large blocks and boulders to be carried along by the overlying ice. These boulders are often deposited hundreds of kilometers from their source, becoming erratics. The term is also sometimes used to describe the similar process of quarrying, which occurs on a smaller scale in fast-moving rivers and streams.[4]
A cylindrical mass of volcanic rock marking the neck of an ancient volcano, especially one exposed by denudation of the surrounding cone.[4]
plumb line
A vertical reference line created by suspending a weight, known as a plumb bob or plummet, from a string above the Earth's surface and allowing it to hang freely in the direction of the pull of gravity. A precursor to the spirit level, plumb lines are used to establish a vertical datum in a wide range of applications, particularly in surveying to determine the nadir of a point in space, and often in combination with an instrument in order to set the instrument precisely over a fixed survey marker.
plunge pool
A deep depression at the base of a waterfall into which the water drops with great force, plucking and abrading the rock beneath and behind the falls and creating an often nearly circular concavity which may remain filled with water long after the waterfall itself dries up.[4]
plural society
A situation in which two or more culture groups occupy the same territory but maintain their separate cultural identities.[2]
point bar
A depositional feature made of alluvium that accumulates on the inside bend of a meandering stream or river, below the slip-off slope and often directly opposite a cut bank. Point bars are usually crescent-shaped beaches of sand, silt, or gravel, similar to shoals and river islands.
polar aspect
A planar map projection with its origin located at either the North or the South geographic pole.[9]
polar circle
Either of the two circles of latitude enclosing the Earth's polar regions: the Arctic Circle in the Northern Hemisphere and the Antarctic Circle in the Southern Hemisphere.
polar ice cap

Also polar ice sheet.

Either of the two very large regions near the Earth's geographical poles that are seasonally or persistently covered in ice, which occurs because high-latitude regions receive less direct solar radiation than other regions and therefore experience much lower surface temperatures. The Earth's polar ice may cover both land and sea, and varies in size seasonally and with long-term climate change. They typically cover a much larger area than true ice caps and are more correctly termed ice sheets.
polar region
Either of the two high-latitude regions surrounding the Earth's geographical poles (the North and South Poles), which are characterized by frigid climates and extensive polar ice caps. The polar region of the Northern Hemisphere is often simply called the Arctic and that of the Southern Hemisphere is called the Antarctic.

Also empolder.

A low-lying tract of land enclosed by dikes, forming an artificial hydrological entity by creating land from a naturally inundated area, e.g. by reclaiming land from a lake or sea, or by building barriers around a floodplain or marsh and then draining it. All polders are eventually below the surrounding water table some or all of the time, making them especially prone to flooding, and they often require continuous draining.
1.  An extreme geographical point, especially one of a pair.
2.  Either of the two points where the Earth's axis of rotation meets its surface, i.e. the geographic poles, representing the northern and southern extremities of terrestrial latitude: the Geographic North Pole and the Geographic South Pole.
3.  Either of the two ends of the geomagnetic field generated by the dynamo in the Earth's core. These ends may refer either to the true magnetic poles, known as the Magnetic North Pole and the Magnetic South Pole, which are not directly opposite each other, or to the antipodal poles of a hypothetical perfect dipole passing through the Earth's center, known as the Geomagnetic North Pole and the Geomagnetic South Pole.
pole of inaccessibility
A location that, with respect to a given geographical criterion, is the most difficult to reach according to that criterion, e.g. the geographical location that is the most distant from the nearest point meeting that criterion. The term most commonly refers to the so-called continental or oceanic poles of inaccessibility, i.e. the point on a given continental landmass that is the furthest distance from a coastline, and the point in the ocean that is the furthest distance from land, respectively.
political geography
The study of both the spatially uneven outcomes of political processes and the ways in which political processes are themselves affected by spatial structures. A sub-discipline of human geography, its primary concerns can be summarized as the relationships between people, state, and territory.

Also karst polje or karst field.

A very large plain found in karstic regions, enclosed within a depression, usually elliptical, with a flat floor either of bare limestone or covered by alluvium, and generally surrounded by steep limestone walls; or more broadly any enclosed or nearly enclosed valley. The term is used primarily in the Slavic-speaking world.
Many-centered; having many nodes.[2]
An area of unfrozen seawater surrounded by an otherwise contiguous area of pack ice or fast ice. Polynyas are often formed along polar coastlines through the action of katabatic winds, but may also form in the open ocean.
A natural or artificial body of standing water that is usually smaller than a lake.
populated place
A place or area with clustered or scattered buildings and a permanent human population (a city, settlement, town, or village) that is referenced with geographic coordinates.[3]
A collection of organisms of the same group or species which live in a particular geographical area. In the context of geography, it often refers to a collection of humans and is represented at the most basic level as the number of people in a given geographically or politically defined space, such as a city, town, region, country, or the entire world.
population geography
A branch of human geography that studies the ways in which spatial variations in the composition, distribution, migration, and growth of populations are related to the nature of places. This often involves factors such as where populations are found and how the size and composition of these populations is regulated by the demographic processes of fertility, mortality, and migration.
positioning system
Any technology or mechanism used to determine the position of an object in space. Numerous methods for determining position have been practiced since ancient times, though modern positioning systems generally rely on electromagnetic and/or satellite-based technologies capable of providing coverage ranging from local or regional to global and accuracy ranging from tens of metres to sub-millimetre.
An economy that gains its basic character from economic activities developed primarily after manufacturing grew to predominance. Most notable would be quaternary economic patterns.[2]
The branch of hydrology that studies rivers, including the processes and phenomena that occur at their sources, main channels, and mouths; the structure and morphology of drainage basins; and the water, thermal, ice, and sediment regimes that affect and are affected by river discharge.
potentiometric surface
See piezometric surface.

Also pot, swirlhole, churn hole, evorsion, rock mill, and eddy mill.

1.  Any smooth, bowl-shaped or cylindrical hollow, generally deeper than it is wide, that is carved into the rocky bed of a watercourse such as a stream or river. Fluvial potholes are created by the grinding action of stones or coarse sediment kept in perpetual motion in the same spot by the turbulence of the current. The term is also used to refer to plunge pools beneath waterfalls, which are created by similar processes. See also kolk.
2.  A vertical or steeply inclined karstic shaft in a limestone deposit.
3.  In the Great Plains of North America, a shallow depression, generally less than 10 acres (4.0 ha) in area, occurring between dunes or on morainic relief on a prairie and often filled by an intermittent pond or marsh.
4.  Another name for a kettle.
5.  Another name for a panhole.
A type of temperate grassland ecosystem dominated by a characteristic composition of grasses, herbs, and shrubs, rather than by trees. The term is used primarily in North America, but similar ecosystems can be found across the world.
Precambrian rock
The oldest rocks, generally more than 600 million years old.[2]
A peninsula connected to the mainland by an extremely narrow neck of land such that the land at its distal end is very close to being an island. See also tied island.
prevailing winds
The direction from which winds most frequently blow at a specific geographic location.[3]
primary sector
That portion of a region's economy devoted to the extraction of basic materials (e.g., mining, lumbering, agriculture).[2]
Prime Meridian
The imaginary line running from north to south through the Royal Observatory in Greenwich, England which is assigned a longitude of 0 degrees and is therefore used as the reference point for all other lines of longitude.[1]
Preceding, in advance of, or in front of the toe or moraine of a glacier, either spatially or temporally.[4]
The natural extension of a shoreline into a body of water by the gradual accumulation of sediment over time,[13] especially as a result of fluvial sedimentation processes, such as the protrusion of a river delta into the sea. This occurs when the volume of sediment carried by the river and deposited at its mouth exceeds the volume lost through subsidence, sea level rise, or coastal erosion.
A raised mass of land that projects into a lowland or a body of water. Compare headland and cape.
protected area
Any clearly defined geographic space in which human occupation or the exploitation of resources is limited or forbidden through legal or other effective means because of the area's recognized natural, ecological, cultural, or historical value.
A type of second-level administrative division within a country or federal state.
public land
Any land area held and managed in the public domain by a federal or local government.
A type of Indian village constructed by some tribes in the southwestern United States. A large community dwelling, divided into many rooms, up to five stories high, and usually made of adobe. This is also a Spanish word for town or village.[2]
An ecoregion in the central Andes Mountains of South America, or any of the various high-altitude ecosystems encompassing it, including cold deserts and alpine grasslands.



Also abbreviated quad.

A standard division of the Earth's surface area used in maps produced by the United States Geological Survey. Quadrangles are four-sided polygons of varying size, depending on the map series; for example, 7.5-minute quadrangles divide the mapped surface into quadrilaterals measuring 7.5 minutes (0.125 degrees) of latitude by 7.5 minutes of longitude, with each 7.5-minute map showing the topographical detail within one particular quadrilateral of this size. Because the boundaries of quadrangles are based on lines of latitude and longitude, the northern and southern limits of a quadrangle map are not straight lines, and the eastern and western limits are usually not parallel; the actual surface area covered by each map varies with the latitudes depicted.
See bog.
A place from which stone, rock, sand, gravel, slate, or aggregate is excavated from the ground, especially a large man-made pit that is exposed to the open air.


rail gauge
The distance between the two rails of a railroad.[2]
railroad bed
The track or trace of a railroad route, commonly raised slightly above the adjacent natural ground surface and constructed mostly of locally occurring, earthy materials (e.g. gravel and rock fragments).[5]
rain shadow
An area on the leeward (downwind) side of a mountain or mountain range that receives greatly diminished precipitation.[2]
Any forest characterized by abundant rainfall, dense layers of vegetation, and extremely high biodiversity. Rainforests are found in both tropical and temperate regions. The term jungle is sometimes used to refer to a tropical rainforest.
A sloping terrace on a mountainside or rock face. The term is used primarily in Scotland.[4]
A representation of spatial data within a two-dimensional image that defines space as a rectangular array or grid of equally sized cells arranged in rows and columns, where each cell can be identified with location coordinates and is associated with attribute values containing a discrete amount of information from one or more layers or "bands". Raster models are useful for storing and presenting large amounts of complex multivariate data that vary continuously across space, as is commonly encountered in maps, aerial photographs, satellite imagery, and many other aspects of geographic information science. Raster data are contrasted with vector data, which instead store and represent geographic information in the form of points, lines, and polygons.[9]
A fluvial slope landform of relatively steep sides, sometimes with an intermittent stream flowing along the downslope channel. Ravines are typically narrower and shallower than canyons, larger than gullies, and smaller than valleys.
See draw.
reclaimed land
1.  Any land area that is artificially created from earthy fill material that has been intentionally placed and shaped so as to approximate natural contours, especially as part of land reclamation efforts such as those designed to bury tailings following the cessation of mining operations.
2.  An area of land, commonly submerged underwater in its natural state, that has been protected by artificial structures such as dikes and drained for agricultural or other purposes (e.g. a polder).[5]
A submerged ridge-like or mound-like structure built by sedentary calcareous organisms, especially corals, in shallow marine waters, and consisting primarily of their skeletal remains, though often still supporting living colonies as well. Reefs may also be partially composed of rocks, sand, gravel, or seashells. They are locally prominent above surrounding sediments deposited on the sea floor, rising to or nearly to the water's surface.[5]
reference ellipsoid
A mathematically defined surface that approximates the geoid for use in spatial reference systems or geodetic datum definitions. Because of their relative simplicity, reference ellipsoids are used in geographic applications as preferred surfaces on which geodetic network computations are performed and point coordinates such as latitude, longitude, and elevation are defined.
See desert pavement.[4]
An area having some characteristic or characteristics that distinguish it from other areas; a territory that is of interest to people, for which one or more distinctive traits (e.g. climate, economy, history, etc.) define its identity.[2]
1.  The feeling or expression of a common sense of identity, purpose, or group consciousness associated with a particular geographical region, e.g. the Southern United States, Scandinavia, or Lower Egypt, often combined with the creation of institutions that accommodate that particular identity and shape public action.[4]
2.  A movement to decentralize central government, placing administrative responsibility instead at a level intermediate between that of the state and that of smaller local or municipal units.[4]
3.  In architecture, an approach that strives to counter placelessness and lack of identity by incorporating elements of the building's geographical context in its design.
A city located outside the core of a metropolitan area that serves as an independent driving force for political, economic, or cultural development within a larger region. Contrast metropolis.
A layer of loose, unconsolidated, heterogeneous superficial deposits (e.g. soil, sediments, broken rock, volcanic ash, wind-blown material, etc.) overlying solid bedrock.[4]
relative height
See topographic prominence.
relative relief
The elevation or altitude of one location relative to another location; the difference between the highest and lowest points within a given geographical area.[4]
See terrain.
relief map
See topographic map.
(of a particular location) Isolated or inaccessible, either by being physically very distant from another location or by lacking connectivity to transportation or communication networks which would otherwise make exchange between locations convenient.
remote sensing
The gathering of information about an object or place from a remote location (i.e. without making physical on-site observations), most commonly by the use of satellite- or aircraft-based electromagnetic sensor technologies.
representative fraction (RF)
The fraction expressing the ratio between the distance measured between two points on a map and the corresponding actual distance measured between those points in the real world, used to indicate the map's scale. The fraction's numerator is typically 1 (indicating one of some specified unit of length, e.g. inches or centimetres) and the denominator is the number of the same unit in the real world which this length represents on the map. For example, a representative fraction of 11,000,000, often written as 1:1,000,000 or 1:1 mn, means that one inch (or one centimetre) on the map itself is equivalent to one million inches (or centimetres) in the real world. One statute mile is equal to 63,360 inches, so 1,000,000 inches is approximately 16 miles.[4]

Also impoundment.

An artificial lake or an artificially enlarged natural lake that is used to store water. Reservoirs are often created by the construction of a dam or lock in a natural drainage basin.
Anything that is both naturally occurring and of use to humans.[2]
rhumb line

Also loxodrome or simply rhumb.

A line drawn on the surface of a sphere (or on an idealized representation of the Earth) which crosses all meridians of longitude at the same angle, and which therefore has constant bearing relative to true or magnetic north.
A rhumb line or loxodrome spirals toward the north pole of a sphere, crossing all lines of longitude at the same angle.
A rhumb line or loxodrome spirals toward the north pole of a sphere, crossing all lines of longitude at the same angle.
The seaward end of a river valley which has been flooded as a result of a rise in sea level.[12]
ribbon development
The build-up of residential and economic communities along the main routes of communication and transportation radiating from a city or other developed area, because of the advantages of accessibility, relatively inexpensive land, and trade from passers-by.[20]
ribbon lake
A long, narrow, finger-shaped lake, especially one found in a glacial trough and dammed by a rock bar or moraine.
An elongated raised landform which forms a continuous elevated crest for some distance, such as a chain of hills or mountains. The line formed by the highest points, with only lower terrain immediately to either side, is called the ridgeline.
An outcrop of resistant bedrock that forms a bar across a glacial trough and often acts as a dam to impound the waters of a lake.[12]
rift valley
A valley that has formed along a long, narrow continental trough bounded by normal faults; a graben of regional size.
See bergschrund.
riparian rights
The rights of water use possessed by a person owning land containing or bordering a watercourse or lake.[2]
riparian zone
A natural watercourse, usually fresh water, that flows towards an ocean, sea, lake, another river, or in some cases into the ground.
river pocket
An area of land enclosed within the bend of a river, especially where the bend is extended or pronounced (e.g. a meander) and the only road access is along the isthmus. The term is used primarily in Australia.
Located on or inhabiting the banks or the area adjacent to a river or lake. Compare riparian.[2]
A body of water, natural or man-made, that is sheltered from rip currents, spring tides, and swells, and is therefore a known general station in which ships can safely be anchored without dragging or snatching.
rock mill
See pothole.
rôche moutonnée
See sheepback.
1.  A way or course taken in getting from one place to another; an established or selected course of travel or action; a line of travel or means of access, especially when marked by a path, track, road, or rail.
2.  A circuit traveled in delivering, selling, or collecting goods, e.g. by a mail carrier.
The determination of a viable route or line of travel between two places, especially in rugged or unexplored areas such as mountainous terrain or in conditions of poor visibility, and especially when done without the benefits of prior knowledge of the area, maps, or other technology that might aid orienteering, instead relying entirely on recognition of natural features and landmarks and quick estimations of distance, scale, ease, and safety.
An adjective describing any geographic area located outside areas of significant human population such as towns and cities; all population, housing, and territory not included within an urban area is often said to be rural. Rural areas are typified by low population densities, very small settlements, and expansive areas of agricultural land or wilderness.


For a given pair of mountain summits, the region surrounding the elevational low point or col on the ridge connecting the two summits; mathematically, it is the critical point that is simultaneously a relative minimum in one axial direction (e.g. between the peaks) and a relative maximum in the perpendicular direction. Assuming it is navigable, a saddle can be thought of as the area surrounding the highest point on the lowest route which one could use to pass between the two summits.
The saddle is the highest point of the pass between the two mountains.
The saddle is the highest point of the pass between the two mountains.

Also panhandle, chimney (if protruding northward), or bootheel (if protruding southward).

Any narrow, elongated protrusion of a larger territory, either physical or political, such as a state.[2]
salt marsh

Also tidal flat or sea marsh.

A natural coastal marsh ecosystem in the upper intertidal zone, between land and open seawater or brackish water, that is regularly flooded by the tide at high water. Salt marshes support dense stands of terrestrial salt-tolerant plants, especially grasses and low shrubs, which trap and bind sediments from the ocean and help protect the nearby shoreline from coastal erosion.
salt pan

Also salt flat.

A large, flat expanse of land naturally covered with salt and/or other minerals, usually to the exclusion of virtually all vegetation. Salt pans are common in deserts, where they form by the precipitation of dissolved mineral solids as a large body of water evaporates. See also playa.

Also seawater.

Any naturally occurring water, especially the water from a sea or ocean, characterized by high concentrations (between 3 and 5% by volume) of dissolved salts, primarily sodium and chloride ions, relative to fresh water or brackish water. Salt water in the Earth's oceans has an average salinity of about 3.5%; it is both denser and freezes at a lower temperature than fresh water.
sand dune
See dune.
sand sea
See erg.
See shoal.
See outwash plain.
satellite navigation

Also satnav.

A method of navigation or an autonomous geospatial positioning system that relies on artificial satellites in orbit around the Earth to transmit time signals at radio frequencies along a line of sight to electronic receivers on the surface, which can then use this information to determine their location, direction, and the current local time to high precision. Satnav systems operate independently of telephonic or internet connectivity, though simultaneous use of these technologies can enhance the accuracy and usefulness of the positioning information generated.
satellite state
A formally independent state or polity which nevertheless depends economically, politically, or militarily upon, or is strongly influenced or controlled by, another, more powerful state.[4]

Also savannah.

A mixed woodland-grassland ecosystem characterized by scattered trees and bushes that are sufficiently widely spaced that the canopy does not close, permitting enough sunlight to reach the ground to support an unbroken herbaceous layer of primarily xerophytic grasses. The term is used especially to refer to the vast, hot, arid grasslands covering parts of equatorial Africa, South America, and northern Australia, but is also sometimes applied more broadly.[4]
The relationship between a linear measurement on a map and the distance it represents on the Earth's surface.[1]

Also escarpment.

A steep cliff face or slope terminating an elevated surface of low relief,[4] formed either because of faulting or by the erosion of inclined rock strata.[2]
See bergschrund.
1.  A narrow stretch of floodplain added to the outer end and downstream side of spurs between enclosed meanders on a river.[4]
2.  A type of point bar consisting of a low, narrow ridge running in line with the curve of a meander, formed when the river overflows its banks.[4]
1.  Any large body of salt water surrounded in whole or in part by land.
2.  Any large subdivision of the World Ocean. "The sea" is the colloquial term for the entire interconnected system of salty bodies of water, including oceans, that covers the Earth.
sea lane

Also sea road, seaway, or shipping lane.

A navigable route across a wide waterway such as an ocean, sea, or large lake that is regularly used for maritime trade by large vessels or ships because it is safe, direct, and economical.
sea level
The average level of the surface of one or more of Earth's oceans from which heights such as elevation and altitude are commonly measured. Often called mean sea level (MSL), it is a type of standardized geodetic vertical datum that is used in numerous applications, including surveying, cartography, and navigation. Mean sea level is commonly defined as the midpoint between the mean low and mean high tides at a particular location.[1]
sea stack
See stack.

Also sea floor or ocean floor.

The bottom of a sea or ocean. As with land terrain, the ocean floor may have ridges, mountains, valleys, and plains.
A mountain (often a volcano) rising from the ocean floor whose summit does not reach the water's surface and which is therefore entirely submerged and not an island or islet.
search space
In human geography, the locations within an area where an individual or group searches for the resources necessary to meet their specific needs (e.g. for housing or employment), based on information from their current awareness space.[4]
See sea lane.
second home
A seasonally occupied dwelling that is not the primary residence of the owner. Such residences are usually found in areas with substantial opportunities for recreation or tourist activity.[2]
secondary-intercardinal directions
The set of eight intermediate directions used in cartography and navigation, each of which is located halfway between a pair of intercardinal directions: north-northeast (NNE), east-northeast (ENE), east-southeast (ESE), south-southeast (SSE), south-southwest (SSW), west-southwest (WSW), west-northwest (WNW), and north-northwest (NNW). They may or may not be explicitly labeled on a compass rose.
secondary sector
That portion of a region's economy devoted to the processing of basic materials extracted by the primary sector.[2]
sector principle
The principle on which political claims to territory in the polar regions have historically been made, such that the territories are divided into arbitrary wedge-shaped sectors, each one having an apex at the geographic pole and including outer areas of both land and sea extending to a particular latitude. Because of the limited accessibility and generally low material value of both the Arctic and Antarctic, the sector principle has emerged as a means of formally sharing responsibility for these regions between the world's sovereign states.[12]
sedimentary rock
Rock formed by the hardening of material deposited in some process; most commonly sandstone, shale, and limestone.[2]
A scientific instrument that detects and records vibrations (seismic waves) produced by earthquakes.[3]
A dense equatorial forest, especially in the Amazon basin of South America.[4]

Also sérac.

A large block or pillar of glacial ice formed by the intersection of numerous crevasses where the glacier fragments as it reaches a steep slope. Seracs are usually found in icefalls, often in large numbers, in mountainous terrain.

Also locality or populated place.

Any place where people live and form communities.
shadow effect
The phenomenon by which a large, well-served urban center affects the transport services of a nearby smaller town or city, often by drawing producers and consumers away from the smaller settlement and toward the larger one, causing the smaller settlement to be relatively ill-provided with direct services.[4]
See doline.
An area of water of relatively little depth, e.g. in a sea, lake, or river.[4]

Also rôche moutonnée.

A rock formation created by the passage of a glacier over underlying bedrock, which often results in asymmetrical erosional forms created by abrasion on the upstream side of the rock and plucking on the downstream side.
A broad area of very old rocks above sea level that is usually characterized by thin, poor soils and low population densities.[2]
shield volcano
A class of volcano that resembles an inverted warrior's shield, with long gentle slopes produced by multiple eruptions of fluid lava flows.[3]

Also sandbank, sandbar, or gravel bar.

A natural submerged ridge, bank, or bar that consists of or is covered by sand or other unconsolidated material and rises from the bed of a body of water to just below or above the surface.

Also shoreline.

The fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. Compare coast.
shore platform
See wave-cut platform.
shoulder drop
See topographic prominence.
A crater formed when the roof of a cavern collapses, usually found in areas of limestone rock.[2]
The features of a place related to the immediate environment on which the place is located (e.g. terrain, soil, subsurface, geology, groundwater, etc.).[2]
The features of a place related to its location relative to other places (e.g., accessibility, hinterland quality).[2]
A small, rocky islet or reef, often one of a series lying just offshore and parallel to the main trend of the coastline, over which large waves may break at high tide or in stormy weather.[4]
A shallow hole or hollow among coastal sand dunes or mud banks.[4]
slack water

Also slack tide or simply slack.

The brief period of time during which a body of water susceptible to tides is completely unstressed because the tidal stream is almost still, i.e. there is no movement in either direction in the tidal current, usually the period immediately before and after the high and low water marks, prior to the tide reversing direction.
slant range
The line-of-sight distance along the relative direction between two points, especially two points which are not at the same elevation relative to a specific datum. If the two points are at the same elevation, the slant range equals the horizontal distance.[15]
1.  In the southeastern United States, a low-lying swampy or boggy area, overgrown with shrubs and cane grasses and favorable for the growth of the slash pine and related trees.[4]
2.  The debris of felled trees, especially in a forest that has been subjected to slash-and-burn agriculture.[4]
1.  The noticeable track of bare rock or furrowed earth left by the mass movement of soil, mud, snow, or rock under shear stress down a steep slope, as in a landslide or avalanche.
2.  The mass of material moved or deposited by such an event, and which has become fixed or settled upon the landscape.[5]
slip-off slope
The more gently sloping of the two banks of a river or stream, usually on the inside bend of a meander, as opposed to a cut bank.[13]
Cross-section of a meandering river: uneven currents result in asymmetrical channels with a gently sloping depositional bank, known as a slip-off slope, on the inside of each bend and a steep erosional bank, known as a cut bank, on the opposite side.
Cross-section of a meandering river: uneven currents result in asymmetrical channels with a gently sloping depositional bank, known as a slip-off slope, on the inside of each bend and a steep erosional bank, known as a cut bank, on the opposite side.
The upward or downward inclination of a natural or artificial surface (e.g. a hillside or a road), or the degree or nature of such an incline; a deviation from the perpendicular or horizontal direction (these directions generally being assigned with respect to the direction of the force of gravity).[4] See also grade.
A type of wetland – usually a swamp, a shallow lake, or a backwater branching from or feeding into a river – in which water tends to be stagnant or flows only very slowly on a seasonal basis.
A residential settlement or neighborhood, usually in or near an urban area, characterized by densely packed and poorly built or dilapidated housing units such as shacks and a deterioration or lack of civic infrastructure such as reliable water, electricity, sanitation, law enforcement, and other basic services, and usually associated with extreme poverty and overpopulation.[4]
A mixture of particulate matter and chemical pollutants in the lower atmosphere, usually over urban areas.[2]
Standard Metropolitan Statistical Area (SMSA)
A statistical unit of one or more counties that focus on one or more central cities larger than a specified size, or with a total population larger than a specified size. This is a reflection of urbanization.[2]

Also terminus or toe.

The lowermost margin or extremity of a glacier, always either gradually advancing or retreating, sometimes partially hidden by morainic material, and commonly featuring a cave from which meltwater flows.[4]
The lowest elevation at which snow remains throughout the year if the summer warmth does not completely melt the winter accumulation, e.g. on a high mountain. This elevation varies widely with latitude, local climate, directional aspect, and steepness of slope, such that the snowline may be very different on different mountains in the same range, on different faces of the same mountain, or on the same face in different years.[3]
soil horizon
A distinct layer of soil encountered in vertical section.[2]
solution pan
See panhole.
The degree to which a substance can be dissolved in another substance; in a geographical context, the characteristic of soil minerals that leads them to be carried away in solution by water. See also leaching.[2]
1.  A large inlet of a sea or ocean that is larger than a bay, deeper than a bight, and wider than a fjord.
2.  A narrow sea or ocean channel between two landmasses.
South Geographic Pole

Also called the Geographic South Pole, Geographic South, or simply the South Pole.

The point in the Southern Hemisphere where the Earth's axis of rotation meets its surface. It is the southernmost point on Earth, directly opposite the North Geographic Pole, and is located on continental land in Antarctica at a latitude of 90 degrees South; its longitude can be assigned any degree value. See also South Magnetic Pole.
South Geomagnetic Pole

Also called the Geomagnetic South Pole.

The point in the Southern Hemisphere where the axis of a theoretical simplified dipole passing through the center of the Earth would intersect the Earth's surface. It is antipodal to the North Geomagnetic Pole. Because of the fluid nature of the Earth's molten core, the true axis of the Earth's magnetic field is not a perfect dipole, and so the Geomagnetic Poles and the actual Magnetic Poles lie some distance apart.
South Magnetic Pole

Also called the Magnetic South Pole or Magnetic South.

The point in the Southern Hemisphere at which the Earth's magnetic field points vertically downward. It is close to but distinct from the Geographic South Pole and the Geomagnetic South Pole</