Category: Geography Dictionary

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.

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

arroyo: 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.

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

archipelago : A collection of islands in a sea.

aquifer : An underground layer of water-bearing permeable rock, rock fractures, or unconsolidated materials such as gravel, sand, or silt.

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.

antipodes : Any pair of points on the Earth’s surface that are diametrically opposite to each other, such that a straight line connecting them would pass through the Earth’s center. Such points are as far away from each other as possible, with the great-circle distance between them being approximately 20,000 kilometres (12,000 mi).

antimeridian : The line of longitude exactly 180 degrees east or west of the Prime Meridian, with which it forms a great circle dividing the Earth into the Eastern and Western Hemispheres. It is used as the approximate basis for the International Date Line because it mostly passes through the open waters of the Pacific Ocean.

anticline : A geological fold 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.

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

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.

altitude : The height of an object in the atmosphere above sea level. Compare elevation

alpine : 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.

alluvium : Clay, silt, gravel, or similar detrital material deposited by running water

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

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 fan : A distinctly triangular, 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.

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

affluent : See tributary.

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

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

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

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.

Palo Verde Nuclear Generating Station: Nuclear power plant located near community of Tonopah west of Phoenix which is the largest power plant in the country for net generation. Palo Verde uses reclaimed water from local cities for condenser cooling water.