| Term | Definition |
|---|
| Abiotic | Pertaining to factors or things that are separate and independent from living things; nonliving |
| Acid | Any compound that releases hydrogen ions when dissolved in water. Also, a water solution that contains a surplus of hydrogen ions |
| Air mass | Enormous bodies of air that move as a unit |
| A layer | A soil horizon below the O layer. Formed of weathered rock, with some organic material; often referred to as topsoil |
| Alkaline | A basic substance; chemically, a substance that absorbs hydrogen ions or releases hydroxyl ions; in reference to natural water, a measure of the base content of the water |
| Aquifer | An underground layer of porous rock, sand, or other material that allows the movement of water between layers of nonporous rock or clay. Frequently tapped for wells |
| Arable | Land that's fit to be cultivated |
| Asthenosphere | The part of the mantle that lies just below the lithosphere |
| Atmosphere | The gaseous mass or envelope surrounding a celestial body, especially the one surrounding the Earth, which is retained by the celestial body's gravitational field |
| Barrier island | A long, relatively narrow island running parallel to the mainland, built up by the action of waves and currents and serving to protect the coast from erosion by surf and tidal surges |
| Biological weathering | Any weathering that's caused by the activities of living organisms |
| Biotic | Living or derived from living things |
| B layer | A soil horizon that receives the minerals and organic materials that are leached out of the A horizon |
| Chemical weathering | The result of chemical interaction with the bedrock that is typical of the action of both water and atmospheric gases |
| C layer | A soil horizon made up of larger pieces of rock that have not undergone much weathering |
| Clay | The finest soil, made up of particles that are less than 0.002 mm in diameter |
| Conduction | The transmission or conveying of something through a medium or passage, especially the transmission of electric charge or heat through a conducting medium without perceptible motion of the medium itself |
| Convection | The vertical movement of a mass of matter due to heating and cooling; this can happen in both the atmosphere and Earth's mantle |
| Convection currents | Air currents caused by the vertical movement of air due to atmospheric heating and cooling |
| Convergent boundary | A plate boundary where two plates are moving toward each other |
| Coral reef | An erosion-resistant marine ridge or mound consisting chiefly of compacted coral together with algal material and biochemically deposited magnesium and calcium carbonates |
| Coriolis effect | The observed effect of the Coriolis force, especially the deflection of an object moving above the Earth, rightward in the Northern Hemisphere, and leftward in the Southern Hemisphere |
| Crop rotation | The practice of alternating the crops grown on a piece of land - for example, corn one year, legumes for two years, and then back to corn |
| Delta | A usually triangular alluvial deposit at the mouth of a river |
| Divergent boundary | A plate boundary at which plates are moving away from each other. This causes an upwelling of magma from the mantle to cool and form new crust |
| Doldrums | A region of the ocean near the equator, characterized by calms, light winds, or squalls |
| Drip irrigation | A method of supplying irrigation |
| Earthquake | The result of vibrations (often due to plate movements) deep in the Earth that release energy. They often occur as two plates slide past one another at a transform boundary |
| El Niño | A climate variation that takes place in tropical Pacific about every three to seven years, for a duration of about one year |
| Erosion | The process of soil particles being carried away by wind or water. Erosion moves the smaller particles first and hence degrades the soil to a coarser, sandier, stonier texture |
| Estuary | The part of the wide lower course of a river where its current is met by the tides |
| Fault | The place where two plates abut each other |
| Greenhouse effect | The phenomenon whereby the Earth's atmosphere traps solar radiation, caused by the presence in the atmosphere of gases such as carbon dioxide, water vapor, and methane that allow incoming sunlight to pass through, but absorb heat radiated back from the Earth's surface |
| Green Revolution | The development and introduction of new varieties of (mainly) wheat and rice that has increased yields per acre dramatically in countries since the 1960s |
| Hadley cell | A system of vertical and horizontal air circulation predominating in tropical and subtropical regions and creating major weather patterns |
| Headwaters | The water from which a river rises; a source |
| Horizon | A layer of soil |
| Humus | The dark, crumbly, nutrient-rich material that results from the decomposition of organic material |
| Hurricane | A severe tropical cyclone originating in the equatorial regions of the Atlantic Ocean or Caribbean Sea or eastern regions of the Pacific Ocean, traveling north, northwest, or northeast from its point of origin, and usually involving heavy rains |
| Inner core | The molten core of the Earth |
| Insolation | The rate of delivery of solar radiation per unit of horizontal surface |
| Jet stream | A high-speed, meandering wind current, generally moving from a westerly direction at speeds often exceeding 400 km (250 miles) per hour at altitudes of 15 to 25 km (10 to 15 miles) |
| Land degradation | When soil becomes water-logged and then dries out, and salt forms a layer on its surface |
| La Niña | A cooling of the ocean surface off the western coast of South America, occurring periodically every 4 to 12 years and affecting Pacific and other weather patterns |
| Lithosphere | The outer part of the Earth, consisting of the crust and upper mantle, approximately 100 km (62 miles) thick |
| Loamy | Soil composed of a mixture of sand, clay, silt, and other organic matter |
| Mantle | The layer of the Earth between the crust and the core |
| Monoculture | The cultivation of a single crop on a farm or in a region or country; a single, homogeneous culture without diversity or dissension |
| Monsoon | A wind system that influences large climactic regions and reverses direction seasonally |
| O layer | The uppermost horizon of soil. It is primarily made up of organic material, including waste from organisms, the bodies of decomposing organisms, and live organisms |
| Physical (mechanical) weathering | Any process that breaks rock down into smaller pieces without changing the chemistry of the rock; typically wind and water |
| Plate boundaries | The edges of tectonic plates |
| Prior appropriation | When water rights are given to those who have historically used the water in a certain area |
| Rain shadow | The low-rainfall region that exists in the leeward (downwind) side of a mountain range. The rain shadow is the result of the mountain range's causing precipitation on the windward side |
| Red tide | A bloom of dinoflagellates that causes reddish discoloration of coastal ocean waters. Certain dinoflagellates of the genus Gonyamlax produce toxins that kill fish and contaminate shellfish |
| R horizon | The bedrock, which lies below all of the other layers of soil |
| Riparian right | The right, as to fishing or to the use of a riverbed, of one who owns riparian land (the land adjacent to a river or stream) |
| Salinization | The process in which soil becomes saltier and saltier until, finally, the salt prevents the growth of plants. Salinization is caused by irrigation because salts brought in with the water remain in the soil as water evaporates |
| Sand | The coarsest soil, with particles 0.05-2.0 mm in diameter |
| Silt | Soil with particles 0.002-0.05 mm in diameter |
| Southern Oscillation | The atmospheric pressure conditions corresponding to the periodic warming of El Niño and cooling of La Niña |
| Subduction zone | In tectonic plates, the site at which an oceanic plate is sliding under a continental plate |
| Thermocline | A layer in a large body of water, such as a lake, that sharply separates regions differing in temperature, so that the temperature gradient across the layer is abrupt |
| Thermosphere | The outermost shell of the atmosphere, between the mesosphere and outer space, where temperatures increase steadily with altitude |
| Topsoil | The A layer of soil; the layer of soil most important for plant growth |
| Trade winds | The more or less constant winds blowing in horizontal directions over the Earth's surface, as part of Hadley cells |
| Transform boundary | Also known as transform faults, boundaries at which plates are moving past each other, sideways |
| Tropical storm | A cyclonic storm having winds ranging from approximately 48 to 121 km (30 to 75 miles) per hour |
| Upwelling | A process in which cold, often nutrient-rich, waters from the ocean depths rise to the surface |
| Volcanoes | An opening in the Earth's crust through which molten lava, ash, and gases are ejected |
| Watershed | The region draining into river system or other body of water |
| Water-scarce | Countries that have a renewable annual water supply of less than 1,000 m³ per person |
| Water-stressed | Countries that have a renewable annual water supply of about 1,000-2,000 m³ per person |
| Weather | The day-to-day variations in temperature, air pressure, wind, humidity, and precipitation mediated by the atmosphere in a given region |
| Weathering | The gradual breakdown of rock into smaller and smaller particles, caused by natural chemical, physical, and biological factors |
| Wetlands | A lowland area, such as a marsh or swamp, that is saturated with moisture, especially when regarded as the natural habitat of wildlife |
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