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. It is split across two articles:
This page, Glossary of geography terms (A–M), lists terms beginning with the letters A through M. Glossary of geography terms (N–Z) lists terms beginning with the letters N through Z. Related terms may be found in Glossary of geology, Glossary of agriculture, Glossary of environmental science, and Glossary of astronomy.
A
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.
accessibility A locational characteristic that permits a place to be reached by the efforts of those at other places.
accessibility resource A naturally emergent landscape form that eases communication between areas.
acculturation The act of adopting a culture different to your own; usually due to immersion into a dominant group.
acme See summit.
acre (ac) A unit of area traditionally defined as the area of a plot of land one chain (66 feet) by one furlong (660 feet), equivalent to 43,560 square feet (0.001563 sq mi; 4,047 m2), or about 0.40 hectare.
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.
adret The sunny, warm aspect of a hill or mountain, as opposed to the ubac or shady side.
affluent 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.
alluvium Clay, silt, gravel, or similar detrital material deposited by flowing water.
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.
altitude The height of an object in the atmosphere above sea level. The term is sometimes used interchangeably with elevation.
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 change appreciably over time (meaning there is no high tide or low tide), and around which a tidal crest circulates once per tidal period (approximately every 12 hours). 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.
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.
anecumene Also anoecumene. The part of the Earth's surface which is uninhabited and/or uninhabitable by human beings. 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.
Antarctic 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. Compare insequent stream.
anthropization The conversion of open spaces, landscapes, and natural environments by human action.
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