Page 724 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

G-5 Glossary
and hills; extensive areas of sand dunes are called sand seas.
Dust dome (4) A dome of airborne pollu- tion associated with every major city; may be blown by winds into elongated plumes down- wind from the city.
Dynamic equilibrium (1) Increasing or de- creasing operations in a system demonstrate a trend over time, a change in average conditions.
Dynamic equilibrium model (14) The bal- ancing act between tectonic uplift and erosion, between the resistance of crust materials and the work of denudation processes. Landscapes evidence ongoing adaptation to rock structure, climate, local relief, and elevation.
Earthquake (13) A sharp release of energy that sends waves travelling through Earth’s crust at the moment of rupture along a fault or in association with volcanic activity. The moment magnitude scale (formerly the Rich- ter scale) estimates earthquake magnitude; intensity is described by the Mercalli scale.
Earth systems science (1) An emerging sci- ence of Earth as a complete, systematic entity. An interacting set of physical, chemical, and biological systems that produce the processes of a whole Earth system. A study of planetary change resulting from system operations; includes a desire for a more quantitative un- derstanding among components rather than a qualitative description.
Ebb tide (16) Falling or lowering tide during the daily tidal cycle. (Compare Flood tide.)
Ecological niche (19) The function, or oper- ation, of a life form within a given ecological community.
Ecological succession (19) The process whereby different and usually more complex assemblages of plants and animals replace old- er and usually simpler communities; communi- ties are in a constant state of change as each spe- cies adapts to changing conditions. Ecosystems do not exhibit a stable point or successional climax condition as previously thought. (See Primary succession, Secondary succession.)
Ecology (19) The science that studies the re- lations between organisms and their environ- ment and among various ecosystems.
Ecosphere (1) Another name for the biosphere.
Ecosystem (19) A self-regulating association of living plants and animals and their nonliv- ing physical and chemical environments.
Ecotone (20) A boundary transition zone be- tween adjoining ecosystems that may vary in width and represent areas of tension as simi- lar species of plants and animals compete for the resources. (See Ecosystem.)
Effusive eruption (13) A volcanic erup- tion characterised by low-viscosity basaltic magma and low gas content, which readily escapes. Lava pours forth onto the surface with relatively small explosions and few pyroclastics; tends to form shield volcanoes. (See Shield volcano, Lava, Pyroclastic; com- pare Explosive eruption.)
Elastic-rebound theory (13) A concept de- scribing the faulting process in Earth’s crust, in which the two sides of a fault appear locked despite the motion of adjoining pieces of crust, but with accumulating strain, they rup- ture suddenly, snapping to new positions rela- tive to each other, generating an earthquake.
Electromagnetic spectrum (2) All the radiant energy produced by the Sun placed in an or- dered range, divided according to wavelengths.
El Niño–Southern Oscillation (ENSO) (6)
Sea-surface temperatures increase, sometimes more than 8 C° above normal in the central and
eastern Pacific, replacing the normally cold, nutrient-rich water along Peru’s coastline. Pressure patterns and surface ocean tempera- tures shift from their usual locations across the Pacific, forming the Southern Oscillation.
Eluviation (18) The removal of finer parti- cles and minerals from the upper horizons of soil; an erosional process within a soil body. (Compare Illuviation.)
Empirical classification (10) A climate clas- sification based on weather statistics or other data; used to determine general climate cat- egories. (Compare Genetic classification.)
Endogenic system (12) The system internal to Earth, driven by radioactive heat derived from sources within the planet. In response, the surface fractures, mountain building occurs, and earthquakes and volcanoes are activated. (Compare Exogenic system.)
Entisols (Appendix B) A soil order in the Soil Taxonomy. Specifically lacks vertical de- velopment of horizons; usually young or unde- veloped. Found in active slopes, alluvial-filled floodplains, and poorly drained tundra.
Environmental lapse rate (3) The actual rate of temperature decrease with increasing altitude in the lower atmosphere at any par- ticular time under local weather conditions; may deviate above or below the normal lapse rate of 6.4 C° per km, or 1000 m. (Compare Normal lapse rate.)
Eolian (16) Caused by wind; refers to the erosion, transportation, and deposition of materials; spelled aeolian in some countries.
Epipedon (18, Appendix B) The diagnostic soil horizon that forms at the surface; not to be confused with the A horizon; may include all or part of the illuviated B horizon.
Equal area (18, Appendix A) A trait of a map projection; indicates the equivalence of all areas on the surface of the map, although shape is distorted. (See Map projection.)
Equatorial Low (6) A thermally caused low- pressure area that almost girdles Earth, with air converging and ascending all along its extent; also called the intertropical conver- gence zone (ITCZ).
Erg (16) An extensive area of sand and dunes; from the Arabic word for “dune field.” (Compare Sand sea.)
Erosion (15) Denudation by wind, water, or ice, which dislodges, dissolves, or removes surface material.
Esker (17) A sinuously curving, narrow de- posit of coarse gravel that forms along a melt- water stream channel, developing in a tunnel beneath a glacier.
Estuary (15) The point at which the mouth of a river enters the sea, where freshwater and seawater are mixed; a place where tides ebb and flow.
water in the oceans.
Eutrophication (19) The gradual enrich- ment of water bodies that occurs with nutri- ent inputs, either natural or human-caused.
Evaporation (9) The movement of free wa- ter molecules away from a wet surface into air that is less than saturated; the phase change of water to water vapour.
Evaporation fog (7) A fog formed when cold air flows over the warm surface of a lake, ocean, or other body of water; forms as the water molecules evaporate from the water sur- face into the cold, overlying air; also known as steam fog or sea smoke.
Evapotranspiration (9) The merging of evaporation and transpiration water loss into one term. (See Potential evapotranspiration, Actual evapotranspiration.)
Evolution (19) A theory that single-cell or- ganisms adapted, modified, and passed along inherited changes to multicellular organisms. The genetic makeup of successive generations is shaped by environmental factors, physio- logical functions, and behaviours that created a greater rate of survival and reproduction and were passed along through natural selection. Exfoliation (14) The physical weathering process that occurs as mechanical forces en- large joints in rock into layers of curved slabs or plates, which peel or slip off in sheets; also called sheeting.
Exogenic system (12) Earth’s external sur- face system, powered by insolation, which energizes air, water, and ice and sets them in motion, under the influence of gravity. In- cludes all processes of landmass denudation. (Compare Endogenic system.)
Exosphere (3) An extremely rarefied outer atmospheric halo beyond the thermopause at an altitude of 480 km; probably composed of hydrogen and helium atoms, with some oxygen atoms and nitrogen molecules present near the thermopause.
Explosive eruption (13) A violent and un- predictable volcanic eruption, the result of magma that is thicker (more viscous), stickier, and higher in gas and silica content than that of an effusive eruption; tends to form block- ages within a volcano; produces composite volcanic landforms. (See Composite volcano; compare Effusive eruption.)
Extrusive igneous rock (12) A rock that so- lidifies and crystallizes from a molten state as it extrudes onto the surface, such as basalt.
Family (18) One of the five levels of hierar- chical generalization of several levels of soil detail and grouping—a subdivision of soil subgroup in the CSSC.
Faulting (13) The process whereby dis- placement and fracturing occur between two portions of Earth’s crust; usually associated with earthquake activity.
Feedback loop (1) Created when a portion of system output is returned as an informa- tion input, causing changes that guide further system operation. (See Negative feedback, Positive feedback.)
Field capacity (9) Water held in the soil by hydrogen bonding against the pull of gravity, remaining after water drains from the larger pore spaces; the available water for plants. (See Capillary water.)
Fire ecology (19) The study of fire as a natu- ral agent and dynamic factor in community succession.
summer season in the zone of accumulation.
Firn line (17) The snow line that is visible on the surface of a glacier, where winter snows survive the summer ablation season; analo- gous to a snow line on land. (See Ablation.)
Fjord (17) A drowned glaciated valley, or glacial trough, along a seacoast.
Flash flood (15) A sudden and short-lived torrent of water that exceeds the capacity of a stream channel; associated with desert and semiarid washes.
Flood (15) A high water level that overflows the natural riverbank along any portion of a stream.
Eustasy (9)
Snow of a granular texture that is transitional in the slow transformation from snow to glacial ice; snow that has persisted through a
Refers to worldwide changes in sea level that are related not to movements of land, but rather to changes in the volume of
Firn (17)