Page 725 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Glossary G-6
Flood basalt (13) An accumulation of hori- zontal flows formed when lava spreads out from elongated fissures onto the surface in extensive sheets; associated with effusive eruptions. (See Basalt.)
Floodplain (15) A flat, low-lying area along a stream channel, created by and subject to recurrent flooding; alluvial deposits generally mask underlying rock.
Flood tide (16) Rising tide during the daily tidal cycle. (Compare Ebb tide.)
Fluvial (15) Stream-related processes; from the Latin fluvius for “river” or “running water.”
Fog (7) A cloud, generally stratiform, in contact with the ground, with visibility usu- ally reduced to less than 1 km.
Folding (13) The bending and deformation of beds of rock strata subjected to compres- sional forces.
Food chain (19) The circuit along which energy flows from producers (plants), which manufacture their own food, to consumers (animals); a one-directional flow of chemical energy, ending with decomposers.
Food web (19) A complex network of inter- connected food chains. (See Food chain.)
Freezing precipitation (8) Freezing rain, ice glaze, or ice pellets.
Friction force (6) The effect of drag by the wind as it moves across a surface; may be operative through 500 m of altitude. Surface friction slows the wind and therefore reduces the effectiveness of the Coriolis force.
Frost wedging (14) A powerful mechanical force produced as water expands up to 9% of its volume as it freezes. Water freezing in a cavity in a rock can break the rock if it ex- ceeds the rock’s tensional strength.
Fusion (2) The process of forcibly joining positively charged hydrogen and helium nu- clei under extreme temperature and pressure; occurs naturally in thermonuclear reactions within stars, such as our Sun.
Gelisols (Appendix B) A new soil order in the Soil Taxonomy, added in 1998, describ- ing cold and frozen soils at high latitudes or high elevations; characteristic tundra vegetation.
General circulation model (GCM) (11) Com- plex, computer-based climate model that pro- duces generalizations of reality and forecasts of future weather and climate conditions. Complex GCMs (three-dimensional models) are in use in the United States and in other countries.
Genetic classification (10) A climate clas- sification that uses causative factors to de- termine climatic regions; for example, an analysis of the effect of interacting air masses. (Compare Empirical classification.)
Geodesy (1) The science that determines Earth’s shape and size through surveys, mathematical means, and remote sensing. (See Geoid.)
Geographic information system (GIS) (1) A computer-based data processing tool or meth- odology used for gathering, manipulating, and analyzing geographic information to pro- duce a holistic, interactive analysis. Geography (1) The science that studies the interdependence and interaction among geo- graphic areas, natural systems, processes, society, and cultural activities over space—a spatial science. The five themes of geographic education are location, place, movement, re- gions, and human–Earth relationships.
Geoid (1) A word that describes Earth’s shape; literally, “the shape of Earth is Earth- shaped.” A theoretical surface at sea level that extends through the continents; deviates from a perfect sphere.
Geologic cycle (12) A general term charac- terising the vast cycling that proceeds in the lithosphere. It encompasses the hydrologic cycle, tectonic cycle, and rock cycle.
Geologic time scale (12) A depiction of eras, periods, and epochs that span Earth’s history; shows both the sequence of rock strata and their absolute dates, as determined by meth- ods such as radioactive isotopic dating.
Geomagnetic reversal (12) A polarity change in Earth’s magnetic field. With uneven regularity, the magnetic field fades to zero and then returns to full strength, but with the magnetic poles reversed. Reversals have been recorded nine times during the past 4 million years.
Geomorphic threshold (14) The threshold up to which landforms change before lurching to a new set of relationships, with rapid re- alignments of landscape materials and slopes.
Geomorphology (12) The science that ana- lyzes and describes the origin, evolution, form, classification, and spatial distribution of landforms.
Geostrophic wind (6) A wind moving be- tween areas of different pressure along a path that is parallel to the isobars. It is a product of the pressure gradient force and the Corio- lis force. (See Isobar, Pressure gradient force, Coriolis force.)
Geothermal energy (12) The energy in steam and hot water heated by subsurface magma near groundwater. Geothermal energy literally refers to heat from Earth’s interior, whereas geothermal power relates to specific applied strategies of geothermal electric or geother- mal direct applications. This energy is used in Iceland, New Zealand, Italy, and northern California, among other locations.
Glacial drift (17) The general term for all glacial deposits, both unsorted (till) and sorted (stratified drift).
Glacial ice (17) A hardened form of ice, very dense in comparison to normal snow or firn.
Glacier (17) A large mass of perennial ice resting on land or floating shelflike in the sea adjacent to the land; formed from the ac- cumulation and recrystallization of snow, which then flows slowly under the pressure of its own weight and the pull of gravity.
Glacier surge (17) The rapid, lurching, un- expected forward movement of a glacier.
Gleiysation (18) A process of humus and clay accumulation in cold, wet climates with poor drainage.
Gleysolic (18) A CSSC soil order defined on the basis of colour and mottling that results from chronic reducing conditions inherent in poorly drained mineral soils under wet con- ditions. High water table and long periods of water saturation.
Global carbon budget (11) The exchange of carbon between sources and sinks in Earth’s atmosphere, hydrosphere, lithosphere, and biosphere.
Global dimming (4) The decline in sunlight reaching Earth’s surface due to pollution, aero- sols, and clouds.
Global Positioning System (GPS) (1)
Latitude, longitude, and elevation are accu- rately calibrated using a handheld instrument that receives radio signals from satellites.
Goode’s homolosine projection (Appendix A)
An equal-area projection formed by splicing
together a sinusoidal and a homolographic projection.
Graben (13) Pairs or groups of faults that produce downward-faulted blocks; charac- teristic of the basins of the interior western United States. (Compare Horst; see Basin and Range Province.)
Graded stream (15) An idealized condition in which a stream’s load and the landscape mutually adjust. This forms a dynamic equi- librium among erosion, transported load, deposition, and the stream’s capacity.
Gradient (15) The drop in elevation from a stream’s headwaters to its mouth, ideally forming a concave slope.
Granite (12) A coarse-grained (slow-cooling) intrusive igneous rock of 25% quartz and more than 50% potassium and sodium feld- spars; characteristic of the continental crust.
Gravitational water (9) That portion of sur- plus water that percolates downward from the capillary zone, pulled by gravity to the groundwater zone.
Gravity (2) The mutual force exerted by the masses of objects that are attracted one to another and produced in an amount propor- tional to each object’s mass.
Great circle (1) Any circle drawn on a globe with its center coinciding with the center of the globe. An infinite number of great cir- cles can be drawn, but only one parallel of latitude—the equator—is a great circle. (Com- pare Small circle.)
Great group (18) One of the five levels of hierarchical generalization of several levels of soil detail and grouping—a subdivision of each of the ten soil orders in the CSSC.
Greenhouse effect (4) The process whereby radiatively active gases (carbon dioxide, water vapour, methane, and CFCs) absorb and emit the energy at longer wavelengths, which are retained longer, delaying the loss of infrared to space. Thus, the lower tropo- sphere is warmed through the radiation and re-radiation of infrared wavelengths. The approximate similarity between this process and that of a greenhouse explains the name.
Greenhouse gases (4) Gases in the lower at- mosphere that delay the passage of longwave radiation to space by absorbing and reradiating specific wavelengths. Earth’s primary green- house gases are carbon dioxide, water vapour, methane, nitrous oxide, and fluorinated gases, such as chlorofluorocarbons (CFCs).
Greenwich Mean Time (GMT) (1) Former world standard time, now reported as Coor- dinated Universal Time (UTC). (See Coordi- nated Universal Time.)
Ground ice (17) The subsurface water that is frozen in regions of permafrost. The mois- ture content of areas with ground ice may vary from nearly absent in regions of drier permafrost to almost 100% in saturated soils.
Groundwater (9) Water beneath the surface that is beyond the soil-root zone; a major source of potable water.
Groundwater mining (9) Pumping an aqui- fer beyond its capacity to flow and recharge; an overuse of the groundwater resource.
Gulf Stream (5) A strong, northward- moving, warm current off the east coast of North America, which carries its water far into the North Atlantic.
Habitat (19) A physical location to which an organism is biologically suited. Most spe- cies have specific habitat parameters and limits.