Category: Dictionary

zenith : The imaginary point on the celestial sphere that is directly above a particular location (i.e. in the vertical direction exactly opposite to the apparent direction of the gravitational force at that location). Contrast nadir.

zoning : The public regulation of land and building use to control the character of a place

yardang : A streamlined protuberance carved from bedrock or any consolidated or semi-consolidated material by the dual action of wind abrasion and erosion, especially one found in a desert.

world map : A map of most or all of the surface of the Earth.

World Geodetic System (WGS) : A standard geographic coordinate system, spheroidal reference ellipsoid (for raw altitude data), and geoid (which defines the nominal sea level) used in cartography, geodesy, and satellite navigation applications worldwide. The latest revision, WGS84, is the standard coordinate system used by the Global Positioning System.

world city : See global city.

windward : The side of a landmass facing the direction from which the wind is blowing. Contrast leeward.

wilderness : Any natural environment which has not been significantly developed or modified by human activity, or within which natural processes operate without human interference. Such areas are considered important for the survival of wild plant and animal species as well as for maintaining biodiversity and ecological stability. Wildernesses are often protected areas.

Western Hemisphere : The half sphere of the Earth that is west of the Prime Meridian and east of the antimeridian. It is opposite the Eastern Hemisphere.

weathering : The breaking of rocks into smaller rocks, gradually becoming soil.

wave-cut platform : Also called a shore platform, wave-cut cliff, or coastal bench.

A flat erosion surface along the shore of a lake, bay, or sea that is formed by the undercutting and eventual collapse of a sea cliff as a result of repetitive wave action.

waterway : Any body of water that is deep, wide, and slow enough to be navigable by watercraft.

watershed : Another name for a drainage divide or drainage basin.

watercourse : Any channel followed by a flowing body of water such as a river or stream, potentially including channels that are dry for part or all of the year.

water table : The level below the land surface at which the subsurface material is fully saturated with water. The depth of the water table reflects the minimum level to which wells must be drilled for water extraction

water pollution : The contamination of water by chemical or biological constituents which make it unfit for use.

water mapping : A collection of data represented as a map showing different aspects related to water supplies.

water gap : A low point or opening in a ridge or mountain range carved by the erosional activity of flowing water and through which water continues to flow in the present day. Contrast wind gap.

wash : See arroyo.

wadi : 1.  Another name for a valley, used primarily in Arabic-speaking parts of the world.

2.  A dry, ephemeral riverbed which contains water only when heavy rainfall occurs.

volcano : A vent (opening) in the Earth’s surface through which magma erupts, or the landform that is constructed by eruptive material

volcanic crater : A type of crater created by volcanic activity, typically shaped like a bowl and containing one or more volcanic vents. Compare caldera.

volcanic avalanche: Also called a debris avalanche.

A large, chaotic mass of soil, rock, and volcanic debris moving swiftly down the slopes of a volcano. Volcanic avalanches can also occur without an eruption due to an earthquake, heavy rainfall, or unstable soil, rock, and volcanic debris

village : A small, clustered human settlement or community, usually larger than a hamlet but smaller than a town and often in rural areas, though the criteria for distinguishing a village can vary considerably in different parts of the world.

viewshed : The geographical area that is visible from a particular location. It includes all surrounding points within line-of-sight of the location and excludes points beyond the horizon or obstructed by terrain and natural or artificial objects.

vent : An opening at the Earth’s surface through which volcanic materials (lava, tephra, and gases) erupt. Vents can be at a volcano‘s summit or on its slopes; they can be circular (craters) or linear (fissures)

vertical exaggeration : A scale used in certain maps, such as raised-relief maps, that deliberately distorts the apparent elevation of the map’s topography in order to emphasize vertical features, which might otherwise appear too small to identify relative to the corresponding horizontal scale.

valley : 1.  A low area between hills or mountains, often with a river running through it.2.  A depression that is longer than it is wide.

vale : Another name for a valley.

urbanization : The process by which a human population shifts from rural to urban residency, the gradual increase in the proportion of people living in urban areas such as towns and cities, and the ways in which human societies respond and adapt to this change. Urbanization may be characterized as a specific condition at a set time (e.g. the proportion of the total population or physical area within a given set of towns or cities) or as an increase in that condition over time. It precipitates enormous social, economic, and environmental changes for the planet as a whole.

urban studies : The study of the development of cities and urban areas, especially from historical, architectural, or civic planning perspectives.

urban sprawl : The unrestricted growth of housing, commercial development, and roads (typically of low densities) over large expanses of land, usually within or near an existing urban or suburban area and with little concern for civic planning. It is often considered a type of urbanization and almost always carries negative connotations.

urban : An adjective describing a settlement with a high population density and a developed infrastructure of built environment; places of this type are variously categorized as cities, towns, or conurbations, or simply called urban areas. Contrast suburban, exurban, and rural.

upland : Sometimes used interchangeably with highland.

Any area of land that is higher in elevation relative to another area, especially one that is populated by low hills or situated atop a plateau. 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. Upland areas are usually characterized by relatively fast-flowing waterways and hilly or rocky terrain. Contrast lowland.

uniform region : A territory with one or more features present throughout which are absent or unimportant elsewhere

underpopulation : Economically, a situation in which an increase in the size of the labor force will result in an increase in per-worker productivity.

tundra : A treeless plain characteristic of the Arctic and subarctic regions

true north : Also called geodetic north.

The direction along the Earth’s surface towards the Geographic North Pole. Geodetic true north differs from magnetic north and grid north, and also very slightly from astronomical true north, which is based on the direction of the north celestial pole.

tropics: Also called the tropical zone or torrid zone.

The region of the Earth’s surface surrounding the Equator and bounded by the Tropic of Cancer (23.4° N latitude) and the Tropic of Capricorn (23.4° S latitude). It is characterized by high annual precipitation and the absence of any significant seasonal variation in temperature. The term is often used more broadly to describe any area possessing what is considered a hot, humid climate

Tropic of Capricorn : The southernmost circle of latitude on the Earth at which the Sun appears directly overhead at its culmination, which lies approximately 23.4 degrees south of the Equator. Its northern equivalent is the Tropic of Cancer.

Tropic of Cancer : The northernmost circle of latitude on the Earth at which the Sun appears directly overhead at its culmination, which lies approximately 23.4 degrees north of the Equator. Its southern equivalent is the Tropic of Capricorn.

tributary : Also called an affluent.

A stream or river that flows into a larger stream or main stem or a lake, rather than directly into a sea or ocean. Contrast distributary.

tree line : The latitudinal or elevational limit of normal tree growth. Beyond this limit (i.e. closer to the poles or at higher elevations) climatic conditions are too severe for such growth and trees are stunted or entirely absent

transhumance : The seasonal movement of people and animals in search of pasture. Commonly, winters are spent in snow-free lowlands and summers in the cooler uplands

transferability : The extent to which a good or service can be moved from one location to another; the relative capacity for spatial interaction

township and range : The rectangular system of land subdivision of much of the agriculturally settled United States west of the Appalachian Mountains, established by the Land Ordinance of 1785.

tor : Also called a castle koppie or kopje.

A prominent, free-standing rock outcrop that rises abruptly from the smooth slopes of a gently rounded hill or ridge. In the United Kingdom, the term is also used to refer to the hill itself.

toponymy : The study of placenames (known as toponyms), their origins, meanings, use, and typology.

topography : The physical features of a place, or the study and depiction of physical features, including terrain relief.

topographic prominence : Also called autonomous height, relative height, or shoulder drop.

A measure of the independence of a mountain or hill defined as the vertical distance between its summit and the lowest contour line encircling it but containing no higher summit within it or, equivalently, the difference between the elevation of the summit and the elevation of the key col. Mountains with high prominence tend to be the highest points in their vicinity.

topographic isolation : The minimum great-circle distance between the summit of a mountain or hill and a point of equal elevation, representing a radius of dominance in which the summit is the highest point.

topographical relief : See terrain.

topographic map : Also called a relief map.

A map that uses contour lines to represent the three-dimensional features of a landscape on a two-dimensional surface

time zone : A region of the globe that observes a uniform standard time for legal, commercial, and social purposes.

time geography: Also called time-space geography.

An interdisciplinary perspective, ontological framework, and visual language in which space and time are used as basic dimensions of analysis of dynamic processes and events, including social and ecological interactions, environmental changes, and biographies of individuals.

time distance : A time measure of how far apart places are (how long does it take to travel from place A to place B?). This may be contrasted with other distance metrics such as geographic distance (how far is it?) and cost-distance (how much will it cost to get there?).

till : See glacial till.

tied island: Also called a land-tied island.

An island that is connected to a mainland only by a narrow spit or tombolo which may or may not be occasionally submerged.

tide pool : A shallow pool of seawater, supplied regularly by incoming tides, that forms on a rocky intertidal shore.

tide : The periodic rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the Earth’s rotation.

thalweg : The line of lowest elevation within a valley or watercourse. Thalwegs often acquire special significance in political geography because disputed borders along rivers are often defined as the river’s thalweg.

tertiary sector : That portion of a region’s economy devoted to service activities (e.g., retail and wholesale operations, transportation, insurance)

territory : A specific area or portion of the Earth’s surface; similar to though distinct from a region.

territorial waters : 1.  A concept of the Law of the Sea defined as a belt of coastal waters extending at most 12 nautical miles (22 km) from the designated baseline (usually defined as the mean low-water line) for a coastal state and regarded as the sovereign territory of the state.2.  Any area of water over which a state has legal jurisdiction, including internal waters, the exclusive economic zone, and potentially others.

terrain : Also called topographical relief or simply relief.

The vertical and horizontal dimensions of a land surface, usually as expressed in terms of elevation, slope, and orientation of geographical features.

tephra : Solid material of all sizes explosively ejected from a volcano into the atmosphere.

temperature inversion : An increase in temperature with height above the Earth’s surface, a reversal of the normal pattern.

tarn: Also called a corrie loch.

A mountain lake or pool of water formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn.

taiga : A moist subarctic coniferous forest that begins where the tundra ends and is dominated by spruces and firs.

syrt : A denudational highland or elevated flatland in Russia and Central Asia; a kind of dissected plateau.