G E O G R A P H Y G L O S S A R Y altitude: the elevation of any point above sea (or ground) level. aquifer: an underground deposit of water. basin: the territory through which rivers that all discharge their waters into the same sea or ocean flow. biodiversity: the variety of plant and animal species in a given place. channel: the land through which the water of a river flows. It is also called a riverbed. cliff: a tall, vertical rock face. Cliffs are usually next to the sea. climate: the typical state of the atmosphere in a particular place. climate change: modification of the Earth's climate (more frequent floods and droughts, more severe heat and cold waves, etc.) related to global warming. delta: a usually triangular-shaped terrain that forms at the mouth of a river when materials the river was carrying are deposited. depression: land situated at a lower altitude than the surrounding land, sometimes below sea level. desertification: the process by which soils degrade into arid land and deserts. drought: the absence of precipitation for longer than is normal for the climate of an area (at least one year). dune: the accumulation of sand due to the action of the wind in a desert or beach area. equinoxes: days that mark the beginning of autumn and the beginning of spring. They take place on approximately the 23rd September and the 21st March. On these days the Sun's rays are perpendicular to the Equator and day and night both last 12 hours in each hemisphere. estuary: the V-shaped mouth of a river, formed by a widening of the channel. In an estuary, fresh water from the river and salt water from the sea mix together. fjord: a former glacial valley flooded by the sea. flow: the amount of water carried by a river. glacier: a large mass of ice created by the accumulation of snow over hundreds of years. Glaciers move at different speeds. global warming: an increase in the temperature of the Earth's surface due to an increase in greenhouse gases produced by human activities. greenhouse effect: a natural process by which a moderate temperature is maintained on Earth. It is caused by the existence of gases in the atmosphere that allow the Sun's heat to reach the Earth's surface and prevent all the heat from escaping again. This natural effect is being intensified by certain human activities, leading to an increase in the Earth's temperature. gully: an irregular watercourse that can experience sudden high floods. hemisphere: each of the two halves into which the Earth is divided. When the Equator is the point of division, we can distinguish between the Northern and Southern hemispheres. When the Prime Meridian is the point of division, we can distinguish between the Western and Eastern hemispheres. humanised landscape: a natural landscape that is modified by humans. iceberg: a large mass of ice that floats on the sea and is moved by the wind and ocean currents. Icebergs form when ice breaks off from a glacier or a continental ice sheet, such as Antarctica. minimum flow: the lowest rate at which water travels through a river channel. mountain range: a group of interlinked mountains that were formed at the same time and are visually distinct from each other. In some areas, mountain ranges are called sierras. natural landscape: an area that has not been modified by human activity. Natural landscapes are primarily the result of the interaction of relief, climate, vegetation and soil. ocean current: a large body of water that moves through the oceans in a similar way to a river. plain: flat terrain at a low altitude relative to the sea. ria: a former river valley that has been flooded by the sea. river basin: the territory occupied by a main river and its tributaries. solstices: days that mark the transition from autumn to winter and from spring to summer. Solstices take place around the 21st December and the 21st June. On these days, the Sun's rays are perpendicular to one of the tropics. stream: a discontinuous flow of water. tide: the daily rise and fall of the sea level caused by the attraction of the Moon and the Sun on water. tornado: a column of air, usually in the shape of a funnel, that rotates at high speed. wadi: a wide channel that is dry for most of the year. Water only flows in a wadi after torrential rain or following a period of rapid melting of ice and snow. waterfall: the flow of water over the edge of a sudden change in the level of the terrain. weather: the atmospheric conditions at a specific time and place. wetland: an area of humid ground covered by shallow water. 302
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