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snowline : The lowest elevation at which snow remains from year to year and does not melt during the summer

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

smog : A mixture of particulate matter and chemical pollutants in the lower atmosphere, usually over urban area

slough : 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.

slope : See grade.

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

slide : 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

situation : The features of a place related to its location relative to other places (e.g., accessibility, hinterland quality)

site : The features of a place related to the immediate environment on which the place is located (e.g. terrain, soil, subsurface, geology, groundwater)

sinkhole : A crater formed when the roof of a cavern collapses, usually found in areas of limestone rock

shore : Also called a shoreline.

The fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. Compare coast.

shoal : Also called a 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.

shield volcano : A volcano that resembles an inverted warrior’s shield. It has long gentle slopes produced by multiple eruptions of fluid lava flows

shield : A broad area of very old rocks above sea level that is usually characterized by thin, poor soils and low population densities

sheepback: Also called a 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.

settlement: Also called a locality or populated place.

Any place where people live and form communities.

serac: 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.

seismograph : A scientific instrument that detects and records vibrations (seismic waves) produced by earthquakes

sedimentary rock : Rock formed by the hardening of material deposited in some process; most commonly sandstone, shale, and limestone

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.

secondary sector : That portion of a region’s economy devoted to the processing of basic materials extracted by the primary sector

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.

seamount : 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.

seabed: 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.

sea : 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 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.

scarp: Also called an escarpment.

A steep cliff or steep slope, formed either because of faulting or by the erosion of inclined rock strata.

scale : The relationship between a linear measurement on a map and the distance it represents on the Earth’s surface

salt water: Also called 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. 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.

salt pan: Also called a 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.

salient :

Also called a 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

saddle : 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.

rural : 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.

riverine : Located on or inhabiting the banks or the area adjacent to a river or lake. Compare riparian

river pocket : An area of land enclosed within the bend of a river, especially where the bend is extended or pronounced and the only road access is along the isthmus. The term is used primarily in Australia

river : A natural watercourse, usually fresh water, that flows towards an ocean, sea, lake, another river, or in some cases into the ground.

riparian rights : The rights of water use possessed by a person owning land containing or bordering a watercourse or lake

rift valley : A valley that has formed along a long, narrow continental trough bounded by normal faults; a graben of regional size.

riegel : 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

ridge : 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.

ribbon lake : A long, narrow, finger-shaped lake, especially one found in a glacial trough and dammed by a rock bar or moraine.

ria : The seaward end of a river valley which has been flooded as a result of a rise in sea level.

rhumb line: Also called a loxodrome or simply a 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.

resource : Anything that is both naturally occurring and of use to humans.

reservoir: Also called an 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.

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.

relief map : See topographic map.

relief : See terrain.

regiopolis : 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.

region : 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 are used as the basis for its identity

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.

reef : 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

re-entrant : See draw.

ravine : A fluvial slope landform of relatively steep sides, sometimes with an intermittent stream flowing along the downslope channel. Ravines are typically considered narrower and shallower than canyons, larger than gullies, and smaller than valleys.

rainforest : 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.

rain shadow : An area on the leeward (downwind) side of a mountain or mountain range that receives greatly diminished precipitation.

rail gauge : The distance between the two rails of a railroad

quarry : A place from which stone, rock, sand, gravel, slate, or aggregate is excavated from the ground. Also sometimes called an open-pit mine.

quadrangle: 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.

pueblo : 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

public land : Any land area held and managed in the public domain by a federal or local government.

province : A type of second-level administrative division within a country or federal state.

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.

province : 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.

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.

prevailing winds : The direction from which winds most frequently blow at a specific geographic location

primary sector : That portion of a region’s economy devoted to the extraction of basic materials (e.g., mining, lumbering, agriculture)

presque-isle : 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.

Precambrian rock : The oldest rocks, generally more than 600 million years old

prairie : 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.

pothole: Also called a 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.

post-industrial : An economy that gains its basic character from economic activities developed primarily after manufacturing grew to predominance. Most notable would be quaternary economic patterns.

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.

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.