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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.

swale : Any shallow channel or trough with gently sloping sides, either natural or artificial. Man-made swales are often designed to manage surface runoff and increase rainwater infiltration.

surveying : The science, technique, and profession of determining the terrestrial or three-dimensional positions of points on the surface of the Earth and the distances and angles between them. These points are often used to draw maps and establish boundaries for property ownership, construction projects, and other purposes required by civil law.

surface water : Water present on the surface of the Earth, such as in a river, lake, wetland, or ocean, as opposed to subsurface water.

summit: Also called acme, apex, peak, and zenith.

A point on a surface that is higher in elevation than all points immediately adjacent to it. Mathematically, it is a local maximum in elevation. The highest point of a hill or mountain is often referred to as the summit.

suburbanization : The process by which a human population shifts from urban to suburban residency, or the gradual increase in the proportion of people choosing to live in suburban neighborhoods which act as satellite communities within commuting distance of larger, centralized urban areas. Suburbanization is inversely related to urbanization.

suburban : An adjective describing a mixed-use or residential area existing either as part of an urban area or as a separate community within commuting distance of a city; a place of this type is called a suburb. Suburbs are often defined by commuter infrastructures and have lower population densities than inner-city neighborhoods.

subduction zone : The place where two lithospheric plates come together, one riding over the other. Most volcanoes on land occur parallel to and inland from the boundary between the two plates.

streambed: Also called a riverbed or simply a bed.

The bottom of the channel of a stream or river, usually covered with rocks, sand, or debris and totally devoid of terrestrial vegetation if the stream has flowed recently. The bed is generally considered the part of the channel up to the normal water line, whereas the bank is the part above the water line.

stream : A natural body of water in which surface water flows between the banks of a channel. Long, large streams are usually called rivers

stratovolcano : Also called a composite volcano.

A steep-sided volcano built by lava flows and tephra deposits

strath : A large river valley, typically wider and shallower than a glen. The term is used primarily in Scotland, Australia, and Canada.

strait : See channel.

steppe : An ecoregion characterized by expansive grassland plains without trees apart from those near rivers and lakes

state : A compulsory political organization with a centralized government that maintains a monopoly of the legitimate use of force within a certain geographical territory. See country.

stand : An area of vegetation dominated by a single species, e.g. a stand of oak trees.

stack: Also called a sea stack.

A coastal landform consisting of a steep and often vertical column or columns of rock above the surface of the sea and formed by erosion due to wave action.

spur : A lateral ridge or other salient landform protruding from the side of a hill, mountain, or the main crest of a ridge and typically surrounded on at least three sides by steep hillsides.

spring : Any location where groundwater naturally emerges from an underground aquifer to the Earth’s surface.

spreading ridges : Places on the ocean floor where lithospheric plates separate and magma erupts. About 80 percent of the Earth’s volcanic activity occurs on the ocean floor

spit : Also called a sandspit.

A type of bar or shoal extending from a beach into an ocean or lake and which develops by the deposition of sediment as a result of longshore drift. Spits form where the direction of the shoreline sharply changes direction, such as at a headland, and often develop a “hooked” or recurve shape at their distal ends.

spatial reference system (SRS) : Also called a coordinate reference system (CRS).

A coordinate-based local, regional, or global system used to locate geographical entities and which defines a specific map projection as well as transformations between different systems.

spatial interaction : Movement between locationally separate places

spatial complementarity : The occurrence of location pairing such that items demanded by one place can be supplied by another

spatial citizenship : The participation of individuals and groups of laypeople in decision-making about spatial planning and social rules in public spaces through the reflexive production and use of geographic media such as maps, virtual globes, and GIS software, particularly in order to question existing perspectives on the appropriation of space and the actions permitted within that space and to negotiate alternative spatial visions.

space economy : The locational pattern of economic activities and their interconnecting linkages

Southern Hemisphere : The half sphere of the Earth that is south of the Equator. It is opposite the Northern Hemisphere.

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, and its precise location varies considerably over time due to frequent magnetic changes in the Earth’s core. Its counterpart in the Northern Hemisphere is the North Magnetic Pole, though the two poles are not directly opposite each other.

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 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.

sound : 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.

solubility : 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 leaching).

soil horizon : A distinct layer of soil encountered in vertical section