Page 731 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Glossary G-12
Scale (1) The ratio of the distance on a map to that in the real world; expressed as a rep- resentative fraction, graphic scale, or written scale.
Scarification (14) Human-induced mass movement of Earth materials, such as large- scale open-pit mining and strip mining.
Scattering (4) Deflection and redirection of insolation by atmospheric gases, dust, ice, and water vapour; the shorter the wavelength, the greater the scattering; thus, skies in the lower atmosphere are blue.
Scientific method (1) An approach that uses applied common sense in an organized and objective manner; based on observation, generalization, formulation, and testing of a hypothesis, ultimately leading to the devel- opment of a theory.
Seafloor spreading (12) As proposed by Hess and Dietz, the mechanism driving the move- ment of the continents; associated with up- welling flows of magma along the worldwide system of mid-ocean ridges. (See Mid-ocean ridge.)
Secondary succession (19) Succession that occurs among plant species in an area where vestiges of a previously functioning commu- nity are present; an area where the natural community has been destroyed or disturbed, but where the underlying soil remains intact.
Sediment (12) Fine-grained mineral matter that is transported and deposited by air, wa- ter, or ice.
Sedimentary rock (12) One of the three ba- sic rock types; formed from the compaction, cementation, and hardening of sediments derived from other rocks. (Compare Igneous rock, Metamorphic rock.)
Sediment transport (15) The movement of rocks and sediment downstream when energy is high in a river or stream.
Seismic wave (12) The shock wave sent through the planet by an earthquake or un- derground nuclear test. Transmission varies according to temperature and the density of various layers within the planet; provides in- direct diagnostic evidence of Earth’s internal structure.
Seismograph (12) A device that measures seismic waves of energy transmitted through- out Earth’s interior or along the crust (also called a seismometer).
Seismometer (13) An instrument used to detect and record the ground motion dur- ing an earthquake caused by seismic waves traveling through Earth’s interior to the sur- face; the instrument records the waves on a graphic plot called a seismogram.
Sensible heat (4) Heat that can be measured with a thermometer; a measure of the con- centration of kinetic energy from molecular motion.
September (autumnal) equinox (2) See Autumnal (September) equinox.
Sheetflow (15) Surface water that moves downslope in a thin film as overland flow; not concentrated in channels larger than rills.
Sheeting (14) A form of weathering associ- ated with fracturing or fragmentation of rock by pressure release; often related to exfolia- tion processes. (See Exfoliation dome.)
Shield volcano (13) A symmetrical moun- tain landform built from effusive eruptions (low-viscosity magma); gently sloped and gradually rising from the surrounding land- scape to a summit crater; typical of the Ha- waiian Islands. (Compare Effusive eruption, Composite volcano.)
Sinkhole (14) Nearly circular depression created by the weathering of karst landscapes with subterranean drainage; also known as a doline in traditional studies; may collapse through the roof of an underground space. (See Karst topography.)
Sling psychrometer (7) A weather instru- ment that measures relative humidity using two thermometers—a dry bulb and a wet bulb—mounted side by side.
Slipface (16) On a sand dune, formed as dune height increases above 30 cm on the leeward side at an angle at which loose mate- rial is stable—its angle of repose (30° to 34°).
Slope (14) A curved, inclined surface that bounds a landform.
Small circle (1) A circle on a globe’s surface that does not share Earth’s center—for ex- ample, all parallels of latitude other than the equator. (Compare Great circle.)
Snowline (17) A temporary line marking the elevation where winter snowfall persists throughout the summer; seasonally, the lowest elevation covered by snow during the summer.
Soil (18) A dynamic natural body made up of fine materials covering Earth’s surface in which plants grow, composed of both mineral and organic matter.
Soil colloid (18) A tiny clay and organic particle in soil; provides a chemically active site for mineral ion adsorption. (See Cation- exchange capacity.)
Soil creep (14) A persistent mass movement of surface soil where individual soil particles are lifted and disturbed by the expansion of soil moisture as it freezes or by grazing live- stock or digging animals.
Soil fertility (18) The ability of soil to support plant productivity when it contains organic substances and clay minerals that absorb water and certain elemental ions needed by plants through adsorption. (See Cation-exchange capacity.)
Soil horizons (18) The various layers ex- posed in a pedon; roughly parallel to the surface and identified as O, A, E, B, C, and R (bedrock).
Soil-moisture recharge (9) Water entering available soil storage spaces.
Soil-moisture storage (9) STRGE; the reten- tion of moisture within soil; it is a savings ac- count that can accept deposits (soil-moisture recharge) or allow withdrawals (soil-moisture utilization) as conditions change.
Soil-moisture utilization (9) The extraction of soil moisture by plants for their needs; ef- ficiency of withdrawal decreases as the soil- moisture storage is reduced.
Soil-moisture zone (9) The area of water stored in soil between the ground surface and the water table. Water in this zone may be available or unavailable to plant roots, depending on soil texture characteristics.
Soil porosity (18) The total volume of space within a soil that is filled with air, gases, or water (as opposed to soil particles or organic matter).
Soil profile (18) A vertical section of soil ex- tending from the surface to the deepest extent of plant roots or to regolith or bedrock.
Soil science (18) Interdisciplinary science of soils. Pedology concerns the origin, classi- fication, distribution, and description of soil. Edaphology focuses on soil as a medium for sustaining higher plants.
Soil Taxonomy (Appendix B) A soil clas- sification system based on observable soil
properties actually seen in the field; pub- lished in 1975 by the U.S. Soil Conservation Service and revised in 1990 and 1998 by the Natural Resources Conservation Service to include 12 soil orders.
Solar constant (2) The amount of insolation intercepted by Earth on a surface perpendicu- lar to the Sun’s rays when Earth is at its average distance from the Sun; a value of 1372 W · m−2 (1.968 calories·cm−2) per minute; averaged over the entire globe at the thermopause.
Solar wind (2) Clouds of ionized (charged) gases emitted by the Sun and travelling in all directions from the Sun’s surface. Effects on Earth include auroras, disturbance of radio signals, and possible influences on weather.
Solonetzic (18) A CSSC soil order where solonetz denotes saline or alkaline soils. Well- to imperfectly-drained mineral soils developed under grasses in semiarid to sub- humid climates. Limited areas of central and north-central Alberta.
Solum (18) A true soil profile in the pedon; ideally, a combination of O, A, E, and B horizons. (See Pedon.)
Spatial (1) The nature or character of physi- cal space, as in an area; occupying or operating within a space. Geography is a spatial science; spatial analysis its essential approach.
Spatial analysis (1) The examination of spa- tial interactions, patterns, and variations over area and/or space; a key integrative approach of geography.
Specific heat (5) The increase of tempera- ture in a material when energy is absorbed; water has a higher specific heat (can store more heat) than a comparable volume of soil or rock.
Specific humidity (7) The mass of water vapour (in grams) per unit mass of air (in kilo- grams) at any specified temperature. The maxi- mum mass of water vapour that a kilogram of air can hold at any specified temperature is termed its maximum specific humidity. (Com- pare Vapour pressure, Relative humidity.)
Speed of light (2) Specifically, 299792 kilo- meters per second, or more than 9.4 trillion kilometers per year—a distance known as a light-year; at light speed, Earth is 8 minutes and 20 seconds from the Sun.
Speleothem (11) A calcium carbonate min- eral deposit in a cave or cavern, such as a stalactite or stalagmite, that forms as water drips or seeps from rock and subsequently evaporates, leaving behind a residue of cal- cium carbonate that builds up over time.
Spheroidal weathering (14) A chemical weathering process in which the sharp edges and corners of boulders and rocks are weath- ered in thin plates that create a rounded, spheroidal form.
Spodosols (Appendix B) A soil order in the Soil Taxonomy. Occurs in northern conifer- ous forests; best developed in cold, moist, for- ested climates; lacks humus and clay in the A horizon, with high acidity associated with podsolization processes.
Spring tide (16) The highest tidal range, which occurs when the Moon and the Sun are in conjunction (at new Moon) or in opposition (at full Moon) stages. (Compare Neap tide.)
Squall line (8) A zone slightly ahead of a fast-advancing cold front where wind pat- terns are rapidly changing and blustery and precipitation is strong.
Stability (7) The condition of a parcel of air with regard to whether it remains where it is or changes its initial position. The parcel is