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Soils II Glossary

acid soil A soil material having a pH of less than 7.0, usually understood to be less than 6.0.
adsorbed water Water held in a soil mass by physiochemical forces and having physical properties substantially different from absorbed water or chemically combined water at the same temperature and pressure.
air-dry The state of dryness of a soil at equilibrium with the moisture content of the surrounding atmosphere; the moisture content depends on the relative humidity and temperature of the surrounding atmosphere.
alkali soil A soil having a high degree of alkalinity (pH 8.5 or higher) or having an exchangeable sodium content (15% or more of the exchange capacity) or both.
bearing capacity The average load per unit area that is required to rupture a supporting soil mass.
breccia A rock composed of coarse angular fragments cemented in a fine grained matrix.
bulk density The mass of dry soil per unit bulk volume. The bulk volume is determined before the soil is dried to constant weight at 105 degrees Celsius. It has been called apparent density.
bulk volume The volume, including the solids and the pores, of a soil mass.
clay As a particle size term: a size fraction less than 0.002mm in equivalent diameter.
compressibility The susceptibility of a soil to decrease in volume when subjected to load.
conservation Protection of the soil against physical loss by erosion or against chemical deterioration; that is excessive loss of fertility by either natural or artificial means.
consistence The resistance of a material to deformation or rupture.
creep Slow mass movement of soil and soil material down rather steep slopes primarily under the influence of gravity but aided by saturation with water and by alternate freezing and thawing. In engineering - general slow displacement under load.
cross-bedding An arrangement in which thin layers of stratified sediment are transverse or oblique to the main plane of stratification.
crushing strength The force required to crush a mass of dry soil, or conversely the resistance of a mass of dry soil to crushing.It is expressed in the units of force per unit area (pressure).
crystal A homogeneous inorganic substance of definite chemical composition bounded by plane surfaces that form definite angles with each other to give the substance a regular geometric form.
drain To provide channels such as open ditches or drain tile so that excess water can be removed by surface or by internal flow. To lose water by percolation.
dry weight percentage The ratio of the weight of any constituent of a soil in the oven dry weight of the soil
erode To wear away or remove the land surface by wind, water or other agents.
fine clay A clay fraction of specified size less than 2 micrometres, usually less than 0.2 micrometres.
fine texture Consisting of or containing large quantities of the fine fractions (silt and clay)
glacial till Unstratified glacial drift deposited directly by ice and consisting of clay sand and gravel and boulders intermingled in any proportion.
gleysation A soil forming process, operating under poor drainage conditions which results in the reduction of iron and other elements and in gray colours, and mottles.
humus The fraction of the soil organic matter that remains after most of the added plant and animal residues have decomposed. It is usually dark coloured. It is also used in a collective term for the surface organic matter deposits: mor, moder, mull, muck.
hydrogenic soil Soil deveoped under the influence of water standing within the profile for prolonged periods; it is formed mainly in cold, humid regions
hydrolysis The process by which a substrate is split to form two end products by the intervention of a molecule of water.
hygroscopic water Water absorbed by a dry soil from an atmosphere of high relative humidity. Water lost from an air dry soil when it is heated to 105 degrees Celcius.
igneous rock Rock formed by the cooling and solidification of magma. It has not changed appreciably since its formation.
illite A hydrous mica.
indicator plants Plants that are characteristic of a specific soil or site condition.
indurated layer A soil layer that has become hardened, generally by cementation of soil particles.
infiltration The downward entry of water into the soil.
landscape All natural features such as fields, forests, and water that distinguish one part of the earth's surface from another part. Usually it is the portion of land or territory that the eye can see in a single view including all its natural characteristics.
landslide A mass of material that has slipped downhill by gravity often assisted by water, when the material is saturated. A rapid movement of a mass of soil, rock, or debris, down a slope.
mass wasting A general term for a variety of processes by which large masses of earth material are moved by gravity from one place to another.
mica A mineral group consisting of phyllosilicates, having sheetlike 2:1 lattice structures, generally with potassium in interlayer position.
mine dump Area covered with overburden and other waste materials from ore and coal mines, quarries and smelters, and usually having little or no vegetative cover.
mine wash Water deposited accumulations of sandy silty or clayey material recently eroded in mining operations. It may clog streams and channels and damage land on which it is deposited.
soil moisture Water contained in the soil.
moisture-weight percentage The moisture content expressed as a percentage of the oven dry weight of the soil
montmorillonite group Clay minerals having 2:1 expanding crystal lattice.Isomorphous substitution causes a net permanent charge balanced by cations in such a manner that water may move between the sheets,giving reversible cation exchange&very plastic properties
mottled zone Layer that is marked with spots or blotches of a redder hue or deeper shades of a hue (chroma).The pattern of mottling and the size, abundance, and colour contrast of the mottles vary markedly and should be specified in the soil description
mottles Spots or blotches of different colour or shades of colour interspersed with the dominant colour.
organic matter The organic fraction of the soil; includes plant&animal residues at various stages of decomposition,cells&tissues of soil organisms,&substances synthesized by the soil population. It is usually determined on soils that have been sieved through a 2mm sieve
ovendry soil Soil that has been dried at 105 degrees Celsius until it has reached a constant weight.
outwash Sediments washed out of flowing water beyond the glacier and laid down as stratified drift. The particle size may vary from boulders to silt.
pans Horizons or layers in soils that are strongly compacted, or very high in clay content.
parent material The unconsolidated and more or less chemically weathered mineral or organic matter from which the solum of a soil has developed by pedogenic processes.
particle density The mass per unit volume of the soil particles. It is usually expressed in grams per cubic centimeter.
peat Unconsolidated soil material consisting largely of undecomposed, or only slightly decomposed, organic matter.
penetrability The ease at which a probe can be pushed into the soil. It may be expressed in units of distance, speed, force, or work, depending on the type of penetrometer used.
physical properties of soil The characteristics, processes or reactions of a soil that are caused by physical forces, and are described by or expressed in, physical terms or equations.
piezometer An instrument for measuring the pressure head of liquids.
piezometric surface The surface at which water will stand in a series of piezometers
plastic soil A soil capable of being molded or deformed continuously and permanently into various shapes by moderate pressure.
pore space The total space not occupied by soil particles in a bulk volume of soil.
quicksand Sand of low bearing capacity caused by the upward flow of water and the resultant decrease in intergranular pressure.
regolith The unconsolidated mantle of weathered rock and soil material overlying solid rock.
relief Elevations of inequalities of a land surface, considered collectively. Land having no evenness or differences of elevation is called level;undulating land is called gentle;rolling land is called strong; hilly land is called very strong.
residual material Unconsolidated and partly weathered minerals formed by the disintegration of consolidated rock in place.
residual soil Soil formed from, or resting on, consolidated rock of the same kind as that from which it was formed and in the same location.
reworked Descriptive of material modified after its preliminary deposition, commonly by water or wind.
runoff The portion of the total precipitation of an area that flows away through stream channels.
sandy Containing large amounts of sand. It may be applied to any one of the soil classes that contains a large percentage of sand.
seepage The escape of water downward through the soil. The emergence of water from the soil along an extensive line of surface in contrast to a spring where the water emerges from a local spot.
slickenside Smoothed surfaces along plane of weaknesses resulting from the movement of one mass of soil against another in soils dominated by swelling clays.
soil formation factors The variable, usually interrelated natural agencies that are responsible for the formation of soil. The factors are: parent rock, climate, organisms, relief and time.
solum The upper horizons of a soil in which the parent material has been modified and in which most plant roots are contained. It usually consists of A and B horizons.
stabilization Chemical or mechanical treatment designed to increase or maintain the stability of a mass of soil or otherwise to improve its engineering process.
Stoke's law Equation relating to the terminal settling velocity of a smooth,rigid sphere in a viscous fluid of known density&viscosity to the diameter of the sphere when subjected to a known force field.Used in particle size analysis of soils by the hydrometer method
stratified drift Materials that are distinctly sorted according to size and weight of their component fragments, indicating a medium of transport (water or wind) more fluid than glacier ice.
stress A directional force acting within a material
substrate That which is spread under i.e. an underlying layer, such as the subsoil.
talus A sloping heap of loose rock fragments lying at the foot of a cliff or a steep slope.
varve A distinct band representing the annual deposit of sedimentary materials, regardless or origin. It usually consists of two layers, a thick light coloured layer of silt and fine sand laid down in the spring&summer...(see notes for remainder of definition)
void Space in a soil mass not occupied by solid mineral matter. This space may be occupied by air, water or other gaseous or liquid material.
void ratio The ratio of the volume of void space to the volume of solid particles in a given soil mass.
soil water Is understood to be the equilibrium solution in the soil.
Created by: rlawrie