| Term | Definition |
|---|
| abrasion | The erosive action that occurs when suspended and saltating sediment particles move along hte bottom and sides of a stream channel. |
| badland | A deeply gullied topography resulting from the fast erosion of easily erodible shales and clays. |
| contour | A line that connects points of equal elevation on a topographic map. |
| cuesta | An asymmetrical ridge in a tilted and eroded series of beds with alternating weak and strong resistance to erosion. One side has a long, gentle slope; the other is a steep cliff formed at the edge of the resistant bed where it is undercut by erosion of a weaker bed beneath. |
| elevation | The altitude, or vertical distance above or below sea level. |
| geomorphology | The study of landscapes and their evolution. |
| hogback | A formation similar to a cuesta with steep, narrow, more or less symmetrical ridges. |
| landform | A characteristic landscape feature on Earth's surface that attained its shape through the processes of erosion and sedimentation; for example, a hill or a valley. |
| mesa | A small, flat elevation with steep slopes on all sides created by differential weathering of bedrock of varying hardness. |
| negative feedback | A process in which one action produces an effect that tends to slow the original action and stabilize the process at a lower rate. |
| plateau | A large, broad, flat area of appreciable elevation above the neighboring terrain. |
| positive feedback | A process in which one action produces an effect that tends to speed up the original action and stabilize the process at a faster rate. |
| relief | The difference between the highest and lowest elevations in a particular area. |
| stream power | The rate at which a stream can erode bedrock and transport its load; the product of stream slope and stream discharge. |
| topography | The general configuration of varying heights that gives shape to Earth's surface. |
| acid rain | Acidic precipitation caused by teh pollution of air with sulfur gases emitted by the smokestacks of power plants that burn coal contianing large amounts of the mineral pyrite, by smelters of sulfie ores, and by some factoreis; and with nitrogen oxide gases emitted by smokestacks and automobile exhausts. These gases react with water to form sulfuric acid and nitric acid. |
| anthropogenic | Arising from human activity. |
| coal bed | A layer or stratum of coal. |
| crude oil | A diverse class of liquids composed of complex hydrocarbons, including long molecular chains comprising dozens of carbon and hydrogen atoms. |
| fossil fuel | An energy resource derived from natural organic materials, from coal to oil and natural gas. |
| geothermal energy | Energy produced when underground water is heated as it passes through a subsurface region of hot rocks. |
| global change | A change in climate that has worldwide effects on the biosphere, atmosphere, and other components of the Earth system. |
| Hubbert's peak | A bell-shaped curve developed by M. King Hubbert predicting that U.S. oil production would begin to decline sometime in the early 1970s. |
| natural gas | Methane gas, CH4, the simplest hydrocarbon. |
| nonrenewable energy source | An energy source produced by geological proceses at a rate much slower than the rate at which we are using it up; for example, fossil fuels. |
| nuclear energy | Energy produced by the fission of uranium-235, which can be used to heat stream and drive turvines to create electricity. |
| oil shale | A fine-grained, clay-rich sedimentary rock containing relatively large amounts of organic matter. |
| oil trap | An impermiable barrier that blocks the upward migration of oil or gas, allowing them to collect beneath the barrier. |
| oil window | A limited range of pressures and temperatures, usually located at depths between about 2 and 5 km, at which crude oil forms. |
| quad | A measure of energy consiting of 1 quadrillion British thermal units (Btu). |
| renewable energy source | An energy source that can be renewed quickly enough to compnesate for our use of it; for example, a forest chopped down for wood can be regrown and harvested again. |
| reserve | A deposit that has already been discovered and can be mined economically and legally at the present time. |
| resource | The entire amount of a given resource that may become available for use in the future, including reserves, plus discovered but currently unprofitable deposits, plus undiscovered deposits that geologists think they may be able to find eventually. |
| solar energy | Energy derived from the sun. |
| stratospheric ozone depletion | The thinning of the layer of ozone in the stratosphere caused by reactions involving humanmade compounds, such as chlorofluorocarbons (CFCs). The stratospheric ozone forms a protective layer that shileds Earth by absorbing cell-damaging ultraviolet radiation. |
| sustainable development | Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. |
| tar sand | A deposit of sand or sandstone containing a tarlike substance called natural bitumen. Natural bitumen is petroleum from which the lighter portions have escaped. |
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