C horizon Refer to soil horizon and Appendix II.
calcan A cutan composed of carbonates.
calcareous soil
Soil containing sufficient free CaCO3 and other carbonates to effervesce visibly or audibly when treated with cold 0.1 M HCl. These soils usually contain from 10 to almost 1000 g kg-1CaCO3 equivalent.
calcic horizon
[soil taxonomy] A diagnostic mineral soil horizon of secondary carbonate enrichment that is >15 cm thick, has a CaCO3 equivalent of >150 g kg-1, and has at least 50 g kg-1more calcium carbonate equivalent than the underlying C horizon (USDA, 1999). Compare calcium carbonate equivalent.
Calcids [soil taxonomy] A suborder of Aridisols that have considerable Ca present (i.e., a calcic or petrocalcic horizon that has its upper boundary within 100 cm of the soil surface). Precipitation is insufficient to leach or even move the carbonates to great depths. Calcids have an aridic soil moisture regime (USDA, 1999; Appendix 1).
calcification (no longer used in SSSA publications) The process or processes of soil formation in which the surface soil is kept sufficiently supplied with calcium to saturate the soil cation exchange sites, or the process of accumulation of calcium in some horizon of the profile, such as the calcic horizon of some Aridisols and Mollisols.
calciphytes (no longer used in SSSA publications) Plants that require or tolerate considerable amounts of calcium or are associated with soils rich in calcium.
calcitan A cutan composed of calcite.
calcitic lime
Limestone containing mostly CaCO3.
calcium carbonate equivalent The content of carbonate in a liming material or calcareous soil calculated as if all of the carbonate is in the form of CaCO3. Compare lime, agricultural.
calcium/magnesium ratio A statement of the relative proportions of available calcium and magnesium in the soil.
caldera A large, more or less circular depression, formed by explosion and/or collapse, which surrounds a volcanic vent or vents, and whose diameter is many times greater than that of the included vent, or vents. ( Jackson, 1997). Compare crater.
caliche
(a) An informal term for a prominent zone near the surface, more or less cemented by secondary carbonates of Ca or Mg precipitated from the soil solution. It may occur as a soft thin soil horizon, as a hard thick bed, or as a surface layer exposed by erosion. Most petrocalcic and some calcic horizons are caliche. (b) (colloquial – Chile, Peru) Alluvium cemented with NaNO3, NaCl, and/or other soluble salts in nitrate deposits.
cambic horizon [soil taxonomy] A diagnostic mineral soil horizon that has a texture of loamy very fine sand or finer, has soil structure rather than rock structure, contains some weatherable minerals, and is characterized by the alteration or removal of mineral material as indicated by mottling or gray colors, stronger chromas or redder hues than in underlying horizons, or the removal of carbonates. The cambic horizon lacks cementation or induration and has too few evidences of illuviation to meet the requirements of the argillic or spodic horizon (USDA, 1999).
Cambids [soil taxonomy] A suborder of Aridisols with the least degree of soil development. These Aridisols have a cambic horizon within 100 cm of the soil surface. They may have other diagnostic horizons, such as a gypsic, petrogypsic, calcic, petrocalcic, but the upper boundary of these horizons must be below 100 cm of the soil surface (i.e., paleofeatures not formed in the present environment). Cambids have an aridic soil moisture regime and warmer than cryic that are not in temperature regimes. Cambids do not have the following diagnostic subsurface horizons or features: argillic, natric, salic, or duripan (USDA, 1999; Appendix I).
canyon A long, deep, narrow, very steep-sided valley cut primarily in bedrock with high and precipitous walls in an area of high local relief (e.g., mountain or high plateau terrain), often with a perennial stream at the bottom; similar to but larger than a gorge (Hawley and Parsons, 1980; Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013). Compare gorge, box canyon, slot canyon.
canyon bench A relatively narrow, flat surface along a canyon wall caused by differential erosion of alternating resistant and less-resistant horizontal strata; a type of structural bench ( Jackson, 1997; Schoenenberger and Wysocki, personal communication, 2013). Compare canyon wall. Table 1. Soil water terminology.
canyon wall The steep to near vertical slope between a canyon bottom and higher, adjacent hillslopes or summits of bounding scarps that merge into adjacent uplands above. Canyon walls are generally dominated by rock outcrop and/or bedrock within the soil profile. Canyon walls commonly include cliffs or ledges, and may be a beveled base cut into less resistant rocks (e.g., shale). In large canyons (e.g., Grand Canyon), canyon walls may be vertically interrupted by nearly level or gentle slopes of canyon benches (Schoenenberger and Wysocki, personal communication, 2013).
canyonlands A deeply and extensively dissected landscape composed predominantly of relatively narrow, steep-walled valleys with small flood plains or valley floors; commonly with considerable outcrops of hard bedrock on steep slopes, ledges, or cliffs, and with broader summits or interfluves than found in badlands. Side slopes exhibit extensive erosion, active back-wearing, and relatively sparse vegetation (Schoenenberger and Wysocki, personal communication, 2013).
capacitance probe A device that determines the volumetric soil water content based on the real part of the bulk dielectric permittivity of the soil (Hastead, 1973).
capillary conductivity (no longer used in SSSA publications) Refer to hydraulic conductivity.
capillary fringe Zone immediately above the water table where the soil is saturated but under subatmospheric pressure.
capillary porosity (no longer used in SSSA publications) The small pores, or the bulk volume of small pores, that hold water in soils against a tension usually>60 cm of water. Compare water tension.
capillary potential (no longer used in SSSA publications) As originally proposed by E. Buckingham in 1907, the definition was unconventional with respect to sign, being the negative of the matric potential. Compare Table 1. Soil water terms.
capillary rise Phenomenon that occurs when small pores which reduce the water potential are in contact with free water.
capillary water (no longer used in SSSA publications) The water held in the “capillary” or small pores of a soil, usually with a tension >60 cm of water. Compare soil water, soil water potential.
carbamoylurea Refer to biuret.
carbon cycle The sequence of transformations whereby carbon dioxide is converted to organic forms by photosynthesis or chemosynthesis, recycled through the biosphere (with partial incorporation into sediments), and ultimately returned to its original state through respiration or combustion.
carbon budget Accounting of inputs and outputs of carbon in the soil and ecosystem.
carbon/nitrogen ratio Refer to carbon/organic nitrogen ratio.
carbon/organic nitrogen ratio The ratio of the mass of organic carbon to the mass of organic nitrogen in soil, organic material, plants, or microbial cells.
Carolina Bay Any of various shallow, often oval or elliptical, generally marshy, closed depressions in the Atlantic coastal plain (from southern New Jersey to northeastern Florida, especially developed in the Carolinas). They range from about 100 m to many kilometers in length, are rich in organic matter, and under native conditions contain trees and shrubs different from those of the surrounding areas. Also called Grady ponds (colloquial: Georgia and Alabama) and Delmarva Bays (colloquial: Maryland). Refer to pocosin ( Jackson, 1997).
cartographic unit Refer to map unit, soil; soil map.
cat clay (obselete) Poorly drained, clayey soils, commonly formed in an estuarine environment, that become very acidic when drained due to oxidation of ferrous sulfide.
catabolism The breakdown of organic compounds within an organism.
catch crop (a) A crop produced incidental to the main crop of the farm and usually occupying the land for a short period. (b) A crop grown to replace a main crop that has failed.
category Any one of the ranks of the system of soil classification in which soils are grouped on the basis of their characteristics.
catena (USA) A sequence of soils of about the same age, derived from similar parent material, and occurring under similar climatic conditions, but having different characteristics due to variation in relief and in drainage. Compare toposequence.
cation An atom or atomic group that is positively charged because of a loss in electrons.
cation exchange The interchange between a cation in solution and another cation in the boundary layer between the solution and surface of negatively charged material such as clay or organic matter.
cation exchange capacity (CEC) The sum of exchangeable bases plus total soil acidity at a specific pH values usually 7.0 or 8.0. When acidity is expressed as salt extractable acidity, the cation exchange capacity is called the effective cation exchange capacity (ECEC) because this is considered to be the CEC of the exchanger at the native pH value. It is usually expressed in centimoles of charge per kilogram of exchanger (cmolc kg) or millimoles of charge per kilogram of exchanger (mmolc kg). Compare acidity, total.
catstep (not preferred, refer to terracette) A terracette; especially one produced by slumping of loess deposits as in western Iowa ( Jackson, 1997).
cavitation The formation of gas or water vapor-filled cavities in a liquid volume when the pressure is reduced (tension is increased) to a critical level. In water systems, cavitation typically occurs at about 0.08 MPa of water tension. In confined systems, cavitation can create discontinuity of water columns preventing the nonelastic transmission of pressure along the column across the cavitation.
cemented
Having a hard, brittle consistency because the particles are held together by cementing substances such as humus, CaCO3, or the oxides of silicon, iron, and aluminum. The hardness and brittleness persist even when wet. Compare consistence.
center-pivot Refer to irrigation, center-pivot irrigation.
centripetal drainage pattern A drainage pattern in which the streams converge inward toward a central depression; generally indicative of a structural basin, volcanic crater, caldera, breached dome, bolson, or the end of an eroded anticline or syncline ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013; Way, 1973).
chambers Vesicles or vughs connected by a channel or channels.
channel [microfeature] Small, trough-like, arcuate or sinuous channels separated by small bars or ridges, caused by fluvial processes; common to flood plains and young alluvial terraces; a constituent part of bar and channel topography (Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013; Peterson, 1981).
channer [Scotland, Ireland] Gravel.
channery Refer to rock fragments.
check-basin Refer to irrigation, check-basin.
chelates Organic chemicals with two or more functional groups that can bind with metals to form a ring structure. Soil organic matter can form chelate structures with some metals, especially transition metals, but much metal ion binding in soil organic matter probably does not involve chelation. Artificial chelating compounds are sometimes added to soil to increase the soluble fraction of some metals.
chemical weathering The breakdown of rocks and minerals into new chemical combinations that are stable under prevailing conditions by the presence of water and other components in the soil solution or changes in redox potential (hydrolysis, hydration, carbonation, ion exchange, and solution). Compare weathering, mechanical weathering.
chemical fallow Refer to tillage, chemical fallow.
chemical oxygen demand (COD) A measure of the oxygen-consuming capacity of inorganic and organic matter present in water or wastewater. The COD test, like the BOD test, is used to determine the degree of pollution in an effluent.
chemical potential (a) The rate of change of Gibbs free energy, G, with respect to the number of moles of one component in a mixed chemical system at fixed temperature, pressure ,and number of moles of other components. (b) The chemical potential of a component increases with increasing concentration or partial pressure. Compare activity (chemical).
chemically precipitated phosphorus (no longer used in SSSA publications) Relatively insoluble phosphorus compounds resulting from reactions of phosphorus with soil constituents: e.g., calcium and magnesium phosphates that are precipitated above a pH of about 6.0 to 6.5 (if calcium and magnesium are present); and, iron and aluminum phosphates that are precipitated below a pH of about 5.8 to 6.1. Compare phosphorus fixation.
chemigation The process by which fertilizers, pesticides, and other agrichemicals are applied into irrigation water to fertilize crops, control pests, or amend soils.
chemisorbed phosphorus (no longer used in SSSA publications) Phosphorus adsorbed or precipitated on the surface of clay minerals or other crystalline materials. Compare adsorption, chemically precipitated phosphorus, and phosphorus fixation.
chemodenitrification Nonbiological processes leading to the production of gaseous forms of nitrogen (molecular nitrogen or an oxide of nitrogen).
chemolithotroph
An organism capable of using CO2 or carbonates as the sole source of carbon for cell biosynthesis, and deriving energy from the oxidation of reduced inorganic or organic compounds. Synonym chemolithoautotroph, chemotroph.
chemoorganotroph An organism for which organic compounds serve as both energy and carbon sources for cell synthesis. Synonym heterotroph.
chemostat A device for the continuous culture of microorganisms in which growth rate and population size are regulated by the concentration of a limiting nutrient in incoming medium.
chemotaxis The oriented movement of a motile organism with reference to a chemical agent. May be positive (toward) or negative (away) with respect to the chemical gradient.
chenier A long, narrow, vegetated marine beach ridge or sandy hummock, 1 to 6 m high, forming roughly parallel to a prograding shoreline seaward of marsh and mud-flat deposits, enclosed on the seaward side by finegrained sediments, and resting on foreshore or mud-flat deposits. It is well drained, often supporting trees on higher areas. Widths range from 45 450 m and lengths may exceed several tens of kilometers ( Jackson, 1997).
chenier plain A mud-rich strand plain, occupied by cheniers and intervening mud-flats with marsh and swamp vegetation ( Jackson, 1997). Compare chenier, strand plain.
Chernozem [soil classification](obsolete; not used in soil taxonomy) A zonal great soil group consisting of soils with a thick, nearly black or black, organic matter– rich A horizon high in exchangeable calcium, underlain by a lighter-colored transitional horizon above a zone of calcium carbonate accumulation; occurs in a cool subhumid climate under a vegetation of tail and midgrass prairie (Baldwin et al., 1938).
chert A hard, extremely dense or compact, dull to semivitreous, cryptocrystalline sedimentary rock, consisting dominantly of interlocking crystals of quartz less than about 30 mm in diameter; it may contain amorphous silica (opal). It sometimes contains impurities such as calcite, iron oxide, or the remains of siliceous and other organisms. It has a tough, splintery to conchoidal fracture and may be white or variously colored gray, green, blue, pink, red, yellow, brown, and black. Chert occurs principally as nodular or concretionary segregations in limestones and dolomites ( Jackson, 1997).
Chestnut soil [soil classification] (obsolete; not used in soil taxonomy.) A zonal great soil group consisting of soils with a moderately thick, dark-brown A horizon over a lighter-colored horizon that is above a zone of calcium carbonate accumulation (Baldwin, et al., 1938).
chimney [gilgai] A subsurface feature that forms a crude cone or wave-crest structure centered under a micro-high (e.g., a low mound or rim) and extending at least part-way under adjacent microslopes, composed of substratum material that appears to upwell and reaches close to the surface. A chimney is commonly bounded by master slickensides in the subsoil with maximum angles of dip reaching 60 to 75 degrees under the micro-high. Its morphology is distinct from the soil solum of adjacent micro-lows (e.g., lighter colored and more alkaline and contain carbonate or gypsum concretions absent under micro-lows; Schoeneberger and Wysocki, personal communication, 2013). Compare puff [gilgai], bowl [gilgai], intermediate position [gilgai], gilgai.
chimney and bowl topography (not recommended; use gilgai).
chisel Refer to tillage, chisel.
chlorite
A group of layer silicate minerals of the 2:1 type that has the interlayer filled with a positively charged metal-hydroxide octahedral sheet. There are both trioctahedral (e.g., M = Fe(II), Mg2+, Mn2+, Ni2+) and dioctahedral (M = Al3+, Fe3+, Cr3+) varieties. Compare Appendix I, Table A3.
chopping A method of preparing forest soils for planting or seeding by passing a heavy drum roller with sharp parallel blades over the site to break up organic debris and mix it into the mineral soil.
chroma The relative purity, strength, or saturation of a color; directly related to the dominance of the determining wavelength of the light and inversely related to grayness; one of the three variables of color. Compare Munsell color system; hue; color value.
chronosequence A group of related soils that differ, one from the other, primarily as a result of differences in time as a soil-forming factor.
cinder land [soil survey] A miscellaneous area (map unit) which is composed of loose cinders and other pyroclastic materials. Water holding capacity is very low and trafficability is poor (USDA, 1993).
cinder cone A conical hill formed by the accumulation of cinders and other pyroclastics, normally basaltic or andesitic composition. Slopes generally exceed 20% ( Jackson, 1997).
cinders Uncemented vitric, vesicular, pyroclastic material, >2.0 mm in at least one dimension, with an apparent specific gravity (including vesicles) of >1.0 and<2.0. Compare ash [volcanic], block [volcanic], lapilli, scoria, tephra (Soil Survey Staff, 1994).
circle A form of patterned ground whose horizontal mesh is dominantly circular. Compare nonsorted circle, patterned ground ( Jackson, 1997).
circular gilgai A type of gilgai dominated by circular closed depressions (micro-lows) separated by low mounds (micro-highs); the prevailing type of gilgai on relatively level terrain (slopes < 3%). Distance from micro-high to the center of an adjacent micro-low is generally 4 to 8 m (Schoeneberger and Wysocki, personal communication, 2013). Compare elliptical gilgai, linear gilgai, gilgai.
cirque Semicircular, concave, bowl-like area with steep face, commonly situated at the head of a glaciated mountain valley or high on the side of a mountain, primarily resulting from erosive activity of a mountain glacier. It often contains a small round lake (tarn; Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997). Compare cirque floor, cirque platform, cirque wall.
cirque floor The comparatively level bottom of a cirque, thinly mantled with till and consisting of glacially-scoured knolls and hillocks separated by depressions, flat areas and small lakes (tarn); commonly it is bounded by a slightly elevated rock lip at its exit (Schoeneberger and Wysocki, personal communication, 2013; Holdorf and Donahue, 1990).
cirque headwall The glacially-scoured, steep and arcuate side or wall of a cirque, dominated by rock-outcrops, rubble, and colluvium (Schoeneberger and Wysocki, personal communication, 2013; Holdorf adn Donahue, 1990). Compare headwall.
cirque platform A relatively level or bench-like surface formed by the coalescence of several cirques ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013).
cirque land [soil survey] A miscellaneous area (map unit), which consists of rock outcrop and rubble in a cirque basin; considered largely obsolete (USDA, 1993). Compare cirque.
citrate-soluble phosphorus The fraction of total P in fertilizer that is insoluble in water but soluble in neutral 0.33 M ammonium citrate. Together with water-soluble phosphate, this represents the readily available P content of the fertilizer. Compare phosphate.
class, soil A group of soils defined as having a specific range in one or more particular property(ies) such as acidity, degree of slope, texture, structure, land-use capability, degree of erosion, or drainage. Compare soil structure and soil texture.
classification, soil The systematic arrangement of soils into groups or categories on the basis of their characteristics. Broad groupings are made on the basis of general characteristics and subdivisions on the basis of more detailed differences in specific properties. The USDA soil classification system of soil taxonomy was adopted for use in publications by the National Cooperative Soil Survey on 1 Jan. 1965. Abridged statements of diagnostic features, orders, and suborders are listed alphabetically. The outline of the system is shown in Appendix I (Table A1). Great groups are named by adding a prefix to the suborder name. A list of the connotations of these prefixes is shown in Appendix I (Table A2). For complete definitions of taxa refer to: NRCS (2006).
clast An individual constituent, grain, or fragment of sediment or rock, produced by the mechanical weathering (disintegration) of a larger rock mass (Hawley and Parson, 1980).
clastic [adjective] Pertaining to rock or sediment composed mainly of fragments derived from preexisting rocks or minerals and moved from their place of origin. The term indicates sediment sources that are both within and outside the depositional basin. Compare detritus, epiclastic, pyroclastic, volcaniclastic ( Jackson, 1997).
clay (a) A soil separate consisting of particles <0.002 mm in equivalent diameter. Compare soil separates. (b) A textural class. Compare soil texture. (c) [clay mineralogy] A naturally occurring material composed primarily of fine-grained minerals, which is generally plastic at appropriate water contents and will harden when dried or fired. Although clay usually contains phyllosilicates, it may contain other materials that impart plasticity and harden when dried or fired. Associated phases in clay may include materials that do not impart plasticity and organic matter.
clay coating Synonym clay films.
clay films Coatings of oriented clay on the surfaces of peds and mineral grains and lining pores. Also called clay skins, clay flows, illuviation cutans, or argillans.
clay flows Refer to clay films and cutan.
clay loam A soil textural class. Compare soil texture.
clay mineral A phyllosilicate mineral or a mineral that imparts plasticity to clay and which harden upon drying or firing. Compare phyllosilicate mineral terminology.
clay mineralogy Refer to phyllosilicate mineral terminology.
clay skins Refer to clay films.
clayey (a) Texture group consisting of sandy clay, silty clay, and clay soil textures. Compare soil texture. (b) Family particle-size class for soils with 35% or more clay and <35% rock fragments in upper subsoil horizons.
claypan A dense, compact, slowly permeable layer in the subsoil having a much higher clay content than the overlying material, from which it is separated by a sharply defined boundary. Claypans are usually hard when dry and plastic and sticky when wet.
cleavage plane The smooth, flat surface along which a mineral readily breaks.
cliff Any high, very steep to perpendicular or overhanging face of rock or earth; a precipice. Compare bluff, beveled base ( Jackson, 1997).
climatic index A simple, single numerical value that expresses climatic relationships; for example, the numerical value obtained in Transeau’s precipitation/ evaporation ratio.
climax (no longer used in SSSA publications) The most advanced successional community of plants capable of development under, and in dynamic equilibrium with, the prevailing environment.
climbing dune A dune formed by the piling-up of sand by wind against a cliff or mountain slope; very common in arid regions with substantial local relief and strong, prevailing winds ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013). Compare sand ramp.
climosequence A group of related soils that differ, one from another, primarily as a result of differences in climate as a soil-forming factor.
clod A compact, coherent mass of soil varying in size, usually produced by plowing, digging, etc., especially when these operations are performed on soils that are either too wet or too dry and usually formed by compression, or breaking off from a larger unit, as opposed to a building-up action as in aggregation.
closed depression A generic name for any enclosed area that has no surface drainage outlet and from which water escapes only by evaporation or subsurface drainage; an area of lower ground indicated on a topographic map by a hachured contour line forming a closed loop ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013). Compare open basin.
coalescent fan piedmont (not preferred) Use fan piedmont (Hawley and Parsons, 1980).
coarse fragments An inclusive term for all discrete, water stable, natural fragments in soil > 2 mm diameter; includes fragments of hard rock, wood, pedogenic nodules and concentrations, etc. (excludes artifacts). Compare artifact, rock fragments, pararock fragment.
coarse sand (a) A soil separate. Compare soil separates. (b) A soil textural class. Compare soil texture.
coarse sandy loam A soil textural class. Compare soil texture.
coarse textured Texture group consisting of sand and loamy sand textures. Compare soil texture.
coastal marl An earthy, unconsolidated deposit of gray to buff-colored mud of low bulk density (dry) composed primarily of very fine, almost pure calcium carbonate formed in subaqueous settings that span from freshwater lacustrine conditions (e.g., Florida Everglades) to saline intertidal settings (e.g., Florida Keys) formed by the chemical action of algal mats and organic detritus (periphyton); other marl varieties associated with different environments (e.g., freshwater marl, glauconitic marl) also occur. Coastal marl can be quite pure or it can be finely disseminated throughout living root mats (e.g., mangrove roots) and/or organic soil layers (Schoeneberger and Wysocki, personal communication, 2013). Compare marl, freshwater marl.
coastal plain A low, generally broad plain that has as its margin an oceanic shore and its strata horizontal or gently sloping toward the water, and generally represents a strip of recently prograded or emerged sea floor; e.g., the coastal plain of the southeastern United States, which extends for 3000 km from New Jersey to Texas ( Jackson, 1997).
coating A layer of a substance completely or partly covering a surface of soil material. Coatings include clay coatings, calcite coatings, gypsum coatings, organic coatings, salt coatings, etc.
cobbles Rounded or partially rounded rock or mineral fragments between 75 and 250 mm in diameter. Compare rock fragments. Synonym cobblestones.
cobblestones (not prerferred) Use cobbles. Synonym cobbles. Compare rock fragments.
cobbly Containing appreciable quantities of cobblestones. Compare rock fragments.
cockpit A crudely star-shaped, closed depression (i.e., large sinkhole) in tropical karst having an inverted conical or slightly concave floor, with an irregular or serrate perimeter formed by subsidiary solution channels and corridors into adjacent hills, and surrounded by residual hills with steep, concave side slopes; the dominant type of closed depression in cockpit karst (Schoeneberger and Wysocki, personal communication, 2013; White, 1988; Jackson, 1997). Compare sinkhole, kegel karst.
cockpit karst A karst landscape dominated by subsurface drainage and serrate or star-shaped depressions (cockpits) that range widely in size and density but typically are considerably larger than sinkholes (dolines), and are separated by intermediate residual hills with concave side slopes; a common type of tropical karst (e.g., Jamaica; Schoeneberger and Wysocki, personal communication, 2013; White, 1988). Compare kegel karst, karst.
COD Refer to chemical oxygen demand.
coefficient of curvature
The ratio D30 2/(D10 × D60),
coefficient of linear extensibility (COLE) (a) The percentage of shrinkage in one dimension of a molded soil between two water contents, e.g., between its plastic limit to air dry. (b)Meaure of shrink–swell potential of soil.
coefficient of uniformity
The ratio D60/D10, which that little of the original plain or it’s gradient remain.Outwash sediments commonly cap present-day topography. Compare collapsed lake plain, pitted outwash plain (Schoeneberger and Wysocki, personal communication, 2013; Clayton and Freers, 1967).
cohesion Forces of attraction between like molecules, e.g., water and water.
col A high, narrow, sharp-edged pass or saddle through a divide or between two adjacent peaks in a mountain range; especially a deep pass formed by the headward erosion and intersection of two cirques ( Jackson, 1997). Compare gap, pass, saddle.
coliform A general term for a group of bacteria that inhabit the intestinal tract of humans and other animals. Their presence in water constitutes presumptive evidence for fecal contamination. Includes all aerobic and facultatively anaerobic, gram-negative rods that are nonspore forming and that ferment lactose with gas formation. Escherichia coli and Enterobacter are important members.
collapse sinkhole A type of sinkhole that is formed by collapse of a cave within the underlying soluble which quantifies the shape of the particle-size distribu-tion curve.
collapsed lake plain A lake plain formed on, and bounded by, glacial ice and subsequently “let down” or collapsed by the melting of underlying ice resulting in contortion or folding of the sediments and sedimentary structures. Lacustrine sediments cap present topography (Schoeneberger and Wysocki, personal communication, 2013; Clayton and Freers, 1967). Compare lake plain.
collapsed ice-floored lakebed A lakebed formed in a lake on glacial ice and subsequently “let down” or collapsed by the melting of underlying ice, resulting in contortion or folding of the lacustrine sediment and sedimentary structures. These modified or distorted lacustrine sediments cap present-day topographic highs and generally lie at elevations higher than the surrounding disintegration moraine (Schoeneberger and Wysocki, personal communication, 2013; Clayton and Freers, 1967). Compare collapsed lake plain, collapsed ice-walled lakebed. quantifies the shape of the particle-size distributioncurve.
collapsed ice-walled lakebed A lakebed that formed in a lake bounded by stagnant ice, but floored by solid ground, usually till. Collapse features are limited to the lakebed margins. Presently, these materials and sedimentary structures generally occur as roughly circular-shaped hills of till capped by lacustrine sediments, generally at elevations higher than surrounding disintegration moraine (Schoeneberger and Wysocki, personal communication, 2013; Clayton and Freers, 1967). Compare collapsed ice-floored lakebed, collapsed lake plain.
collapsed outwash plain An outwash plain which forms on glacial ice (inside the glacial margin), and is subsequently let down or collapsed when the underlying ice melts, resulting in contortion or folding of the sediments and sedimentary structures to the extent
colloid A particle, which may be a molecular aggregate, with a diameter of 0.1 to 0.001 μm. Soil clays and soil organic matter are often called soil colloids because they have particle sizes that are within, or approach, colloidal dimensions.
colloidal suspension Suspension in water of particles so finely divided that they will not settle under the action of gravity but will diffuse, even in quiet water, under the random impulses of Brownian motion. Particle sizes range from about 1 mm to about 1 nm; however, there is no sharp differentiation by size between coarse (“true”) suspension and colloidal suspension or between colloidal suspension and solution.
colluvial [adjective] Pertaining to material or processes associated with transportation and/or deposition by mass movement (direct gravitational action) and local, unconcentrated runoff on side slopes and/or at the base of slopes (Hawley and Parson, 1980). Compare alluvial, fluvial.
colluvial apron A landform with a concave to planar surface composed of a thick wedge-shaped deposit of colluvium and/or slope alluvium that forms the base (footslope) of a bluff, escarpment or steep slope (Schoeneberger and Wysocki, personal communication, 2013). Compare beveled base. and Wysocki, personal communication, 2013; Jackson, 1997; White, 1988). Compare solution sinkhole.
colluvial soil (a) An informal term for any soil composed of sediment transported downslope dominantly by gravity (e.g., soil creep). Compare residual soil. (b) (not preferred) Informally applied to any soil composed of sediments transpoted downslope by either gravity (colluvium) and/or slope wash processes (slope alluvium).
colluvium Unconsolidated, unsorted earth material being transported or deposited on sideslopes and/or at the base of slopes by mass movement (e.g., direct gravitational action) and by local, unconcentrated runoff (Hawley and Parsons, 1980). Compare alluvium, slope alluvium, scree, talus, mass movement.
colonization Establishment of a community of microorganisms at a specific site or ecosystem.
colony forming units (cfu) Number of microorganisms that can form colonies when cultured on artifical media using spread plates or pour plates: an indication of the number of viable, culturable microorganisms in a soil or rhizophere sample.
color Refer to soil color, Munsell color system.
color composite (multiband photography) A color picture produced by assigning a color to a particular spectral band. Ordinarily blue is assigned to band 1 or 4 (~500 to 600 nm), green to band 2 or 5 (~600 to 700 nm), and red to band 3 (~ 700 nm to 1 µm) or 7 (~800 nm to 1.1 µm), to form a picture closely approximating a color-infrared photograph.
colter slit Refter to tillage.
columnar soil structure A type of soil structure. Compare soil structure and soil structure types.
cometabolism Transformation of a substrate by a microorganism without deriving energy, carbon, or nutrients from the substrate. The microorganism can transform the substrate into intermediate degradation products but fails to multiply.
commensalism Interaction between two species in which one species derives benefit while the other is unaffected.
community All of the organisms that occupy a common habitat and that interact with one another.
compaction To unite firmly; the act or process of becoming compact.
competence The ability of a current of water or wind to transport sediment, in terms of particle size rather than amount, measured as the diameter of the largest particle transported. It depends upon velocity: a small but swift current, for example, may have greater competence than a larger but slower, moving current.
competition A rivalry between two or more species for a limiting factor in the environment.
complex landslide [mass movement] A category of mass movement processes, associated sediments (complex landslide deposit) or resultant landforms characterized by a composite of several mass movement processes none of which dominates or leaves a prevailing landform. Numerous types of complex landslides can be specified by naming the constituent processes evident (e.g., a complex earth spread – earth flow landslide; Schoeneberger and Wysocki, personal communication, 2013; Varnes, 1978). Compare fall, topple, slide, lateral spread, flow, landslide.
complex, soil Refer to soil complex.
component soil The collection of polypedons or parts of polypedons within a map unit that are members of the taxon (or a kind of miscellaneous unit) for which the map unit is named. Simple or complex names for the component soils are formed from a class name (taxon name) from some categorical level of theU.S. system of soil taxonomy, with or without an additional phase identification for utilitarian features. Compare inclusion and map unit, soil.
composite cone (not preferred) Refer to stratovolcano.
compost Organic residues, or a mixture of organic residues and soil, that have been mixed, piled, and moistened, with or without addition of fertilizer and lime, and generally allowed to undergo thermophilic decomposition until the original organic materials have been substantially altered or decomposed. Sometimes called “artificial manure” or “synthetic manure.” In Europe, the term may refer to a potting mix for container-grown plants.
composting A controlled biological process that converts organic constituents, usually wastes, into humus-like material suitable for use as a soil amendment or organic fertilizer.
compound sinkhole (not preferred) Use karst valley.
compressibility The property of a soil pertaining to its susceptibility to decrease in bulk volume when subjected to a load.
compressibility index The pressure to void ratio on the linear portion of the curve relating the two variables.
concentrated flow A relatively large water flow over or through a relatively narrow course.
concentration The amount of suspended or dissolved particles or elements in a unit volume or unit mass as specified at a given temperature and pressure.
concretion (a) A cemented concentration of a chemical compound, such as calcium carbonate or iron oxide, that can be removed from the soil intact and that has crude internal symmetry organized around a point, line, or plane. (b) (micromorphological) A glaebule with a generally concentric fabric about a center, which may be a point, line, or a plane.
conduction Process by which heat moves in a soil through vibration of atoms.
conductivity probe An instrument used to measure the thermal conductivity of a material.
conductivity, hydraulic Refer to hydraulic conductivity.
cone index The force per unit basal area required to push a cone penetrometer through a specified increment of soil. Compare cone penetrometer.
cone karst A variety of kegel karst topography, common in the tropics (e.g., Puerto Rico, Pacific Basin Islands) characterized by star-shaped depressions, broader valleys, or lagoons at the feet of many steep-sided, coneshaped residual hills and ridges separated by star-shaped depressions, broader valleys, or lagoons. These hills and ridges have steep, convex side slopes and rounded tops that are dissected into secondary karst surfaces with shafts and various forms of karren microfeatures (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997; White, 1988). Compare karst cone, cockpit karst, fluviokarst, sinkhole karst, tower karst.
cone penetrometer An instrument in the form of a cylindrical rod with a cone-shaped tip designed for penetrating soil and for measuring the end-bearing component of penetration resistance. The resistance to penetration developed by the cone equals the vertical force applied to the cone divided by its horizontally projected area. Compare cone index, friction cone penetrometer, and penetration resistance.
conformity The mutual and undisturbed relationship between adjacent sedimentary strata that have been deposited in orderly sequence with little or no evidence of time lapses; true stratigraphic continuity in the sequence of beds without evidence that the lower beds were folded, tilted, or eroded before the higher beds were deposited ( Jackson, 1997). Compare unconformity.
congelifraction (not preferred) Use frost shattering.
congeliturbate (not recommended) Use cryoturbate.
congeliturbation (not recommended) Use cryoturbation.
conglomerate A coarse-grained, clastic sedimentary rock composed of rounded to subangular rock fragments larger than 2 mm, commonly with a matrix of sand and finer material; cements include silica, calcium carbonate, and iron oxides. The consolidated equivalent of gravel. Compare breccia.
conjugated metabolites Metabolically produced compounds that are linked together by covalent binding (complex formation).
conjunctive water use Refer to irrigation, conjunctive water use.
conservation of mass A law that states that mass is neither created nor destroyed in a defined system.
conservation terrace An earthen embankment constructed across a slope for conducting water from above at a regulated flow to prevent accelerated erosion and to conserve water (Schoeneberger and Wysocki, personal communication, 2013). Compare hillslope terrace.
conservative tracer A solute that is chemically and biologically inert (no transformation losses with time) but could exhibit an adsorption capacity that results in loss from solution.
consistence The attributes of soil material as expressed in degree of cohesion and adhesion or in resistance to deformation or rupture. Refer to Table 2.
consistency The manifestations of the forces of cohesion and adhesion acting within the soil at various water contents, as expressed by the relative ease with which a soil can be deformed or ruptured. Engineering descriptions include: (i) the designation of five inplace categories (soft, firm, or medium, stiff, very stiff, and hard) as assessed by thumb and thumbnail penetrability and indentability; and (ii) characterization by the Atterberg limits (i.e., liquid limit, plastic limit, and plasticity number). Compare Atterberg limits, liquid limit, plastic limit, and plasticity number.
consolidation test A test in which the soil specimen is laterally confined in a ring and is compressed between porous plates.
consortia Natural microbial assemblages of two or more species in which each microorganism benefits from the other. The group may collectively carry out some process (i.e., xenobiotic degradation) that no single member can accomplish individually.
constant-charge surface A mineral surface carrying a net electrical charge whose magnitude depends only on the structure and chemical composition of the mineral itself. Constant-charge surfaces in soils usually arise from isomorphous substitution in phyllosilicate clay structures.
constant-potential surface Variable charge surfaces are called constant-potential surfaces because at constant activity of the potential determining ion (e.g., constant pH), the electrical potential difference between the solid surface and the bulk solution is constant. Compare constant-charge surface, pH-dependent charge, and variable charge.
constructional [geomorphology] (adjective) Said of a landform that owes its origin, form, position, or general character to depositional (aggradational) processes, such as the accumulation of sediment (e.g., alluvial fan, volcanic cone; Jackson, 1997). Compare aggradation, destructional, erosional.
constructional surface [geomorphology] A land surface owing its origin and form to depositional processes, with little or no modification by erosion.
consumptive irrigation requirement Refer to irrigation, consumptive irrigation requirement.
contact angle Where water is in contact with a solid surface, the angle occurring on the liquid side of a meniscus or water droplet between the flat solid surface and the gas phase beyond the liquid.
continental glacier A glacier of considerable thickness completely covering a large part of a continent or an area of at least 50,000 square km, obscuring the underlying surface, such as the ice sheets covering Antarctica or Greenland. Continental glaciers occupied northern portions of the coterminous USA and Alaska in the past (e.g., Pleistocene) and usage commonly implies former continental glacier conditions ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013). Compare alpine glacier.
continuity equation An equation representing the three-dimensional flow system that accounts for conservation of mass or energy.
continuous delivery Refer to irrigation, continuous delivery.
continuous permafrost Permafrost occurring everywhere beneath the exposed land surface throughout a geographic region (National Research Council of Canada, 1988). Compare permafrost, discontinuous permafrost, sporadic permafrost.
contour ditch Refer to irrigation, contour ditch.
contour flooding Refer to irrigation, contour flooding.
contour strip cropping Refer to tillage, strip cropping.
contrasting soil A soil that does not share diagnostic criteria and does not behave or perform similar to the soil being compared.
controlled drainage Refer to irrigation, controlled drainage.
controlled traffic Refer to tillage, controlled traffic.
convection A process by which heat, solutes, or particles are transferred from one part of a fluid to another by movement of the fluid itself; also called advection.
convection-dispersion equation (CDE) Also known as the advection-dispersion equation (ADE). Partial differential equation describing the total solute flux as the sum of the passive movement of solute by convection and the solute movement by diffusion and dispersion.
conveyance loss Refer to irrigation, conveyance loss.
copiotrophs Refer to zymogenous flora.
coppice mound (also called coppice dune) Refer to shrub-coppice dune.
coprogenic material [soil survey] Remains of fish excreta and similar materials that occur in some organic soils.
coprogenous earth [soil taxonomy] A type of limnic layer (sedimentary peat) composed predominantly of fecal material derived from aquatic animals (Soil Survey Staff, 1975).
coral island (a) A relict coral reef that stands above sea level and surrounded by water (e.g., Florida Keys). Carbonate sands rich in coral and shell fragments generally mantle the underlying flat coral platform. (b) An oceanic island formed from coral accumulations lying atop or fringing volcanic peaks or platforms (Schoeneberger and Wysocki, personal communication, 2013; Jackson, 1997).
coral limestone An informal term for massive limestone composed primarily of coral and coral fragments commonly associated with marine islands or coral reefs in tropical or subtropical waters (Schoeneberger and Wysocki, personal communication, 2013). Compare coral island.
corda Small, tightly bunched, parallel ridges or corrugations of lava, commonly < 1 m in amplitude (high) and < 3 m in period (wide) on the surface of corded pahoehoe lava (ropy lava; Schoeneberger and Wysocki, personal communication, 2013; Green and Short, 1971).
corrosion [geomorphology] A process of erosion whereby rocks and soil are removed or worn away by natural chemical processes, especially by the solvent action of running water, but also by other reactions, such as hydrolysis, hydration, carbonation, and oxidation ( Jackson, 1997).
corrugate Refer to irrigation, corrugate irrigation.
coulee (colloquial: northwest USA, and ND) A dry or intermittent stream valley or wash with an underfit stream, especially a long, steep-walled gorge representing a Pleistocene overflow channel that carried meltwater from an ice sheet; e.g., the Grand Coulee in Washington State (Hawley and Parsons, 1980).
coulombic forces Those forces caused by electrical attractions and repulsions.
country rock A general term for the non-igneous rock surrounding an igneous intrusion ( Jackson, 1997).
covalent bond The force holding two atoms together that arises from the sharing of electrons.
cove [geomorphology](a) A walled and rounded or cirque-like opening at the head of a small steep valley. (b) (colloquial southern Appalachians, USA) A smooth-floored, somewhat oval-shaped “valley” sheltered by hills or mountains; e.g., Cades Cove in eastern Tennessee ( Jackson, 1997).
cover crop Close-growing crop, that provides soil protection, seeding protection, and soil improvement between periods of normal crop production, or between trees in orchards and vines in vineyards. When plowed under and incorporated into the soil, cover crops may be referred to as green manure crops.
crack Refer to fracture.
cradle and knoll topography Use tree-tip mound and tree-tip pit.
crag and tail An elongate hill or ridge of subglacially streamlined drift, having at the stoss end (up-ice) a steep, often precipitous face or knob of ice-smoothed, resistant bedrock (the “crag”) obstructing the movement of the glacier, and at the lee end (down-ice) a tapering, streamlined, gentle slope (the “tail”) of intact, weaker rock and/ or drift protected by the crag; also called lee-side cone ( Jackson, 1997; Schoeneberger and Wysocki, personal communication, 2013; Goldthwaite and Matsch, 1988). Compare drumlin, drumlinoid ridge, flute, stoss and lee.
crater (not preffered; use volcanic crater).
craton A part of the earth’s crust that has attained stability, and has been minimally deformed for a prolonged period. The term is now restricted to continental areas of largely Precambrian rocks ( Jackson, 1997).
creek [streams] (not preferred, refer to intermittent stream) A general term used throughout the USA (except New England), Canada, and Australia for a small, intermittent stream that is larger than a brook but smaller than a river ( Jackson, 1997).
creep [mass movement] The process, surficial sediments (creep deposit) and/or landform or mantle that results from very slow downslope mass wasting of unconsolidated earthy material down slopes driven primarily by gravity, but facilitated by water saturation and by freeze-thaw. Sometimes redundantly called soil creep (Schoeneberger and Wysocki, personal communication, 2013). Compare mudflow, flow, landslide, solifluction.
crest The commonly linear, narrow top of a ridge, hill, or mountain. It is appropriately applied to elevated areas where retreating backslopes are converging such that these high areas are almost exclusively composed of convex shoulders; (b) (not preferred) Sometimes used as an alternative for the summit hillslope component (Peterson, 1981; Schoeneberger and Wysocki, personal communication, 2013). Compare summit (part b), saddle.
crevasse [geomorphology] A wide breach or crack in the bank of a river or canal; especially one in a natural levee or an artificial bank of the lower Mississippi River ( Jackson, 1997). Compare flood-plain splay, avulsion.
crevasse filling A short, straight ridge of stratified sand and gravel believed to have been deposited in a crevasse of a wasting glacier and left standing after the ice melted; a variety of kame. May also occur as long, sinuous ridges and linear complexes of till or drift ( Jackson, 1997).
crevasse splay (not recommended) use flood-plain splay. Compare crevasse [geomorphology].
critical volume fraction for percolation The lowest fraction volume of a fluid phase (e.g., water) that is required for there to be a continuous fluid pathway across the medium. At a lower fluid saturation, the pathways are discontinuous, and flow only occurs through films (refer to threshold water content).
critical nutrient concentration The nutrient concentration in the plant, or specified plant part, above which additional plant growth response slows. Crop yield, quality, or performance is less than optimum when the concentration is less.
critical path analysis “CPA uses percolation theory to caculate effective conduction properites of disoredered medium.” (Hunt and Ewing, 2009)
critical soil test concentration That concentration at which 95% of maximum relative yield is achieved. Usually coincides with the inflection point of a curvilinear yield response curve.
crop nutrient requirement The amount of nutrients needed to grow a specified yield of a crop plant per unit area.
crop residue management Refer to tillage, crop residue management.
crop residue management system Refer to tillage, crop residue management system.
crop rotation A planned sequence of crops growing in a regularly recurring succession on the same area of land, as contrasted to continuous culture of one crop or growing a variable sequence of crops.
cross cultivation Refer to tillage, cross cultivation.
cross-bedding [sedimentology] (a) Cross-stratification in which the cross-beds are more than 1 cm in thickness. (b) A cross-bedded structure; a cross-bed ( Jackson, 1997). Compare cross-lamination.
cross-lamination (a) Cross-stratification characterized by cross-beds that are less than 1 cm in thickness.(b) A cross-laminated structure; a cross-lamina ( Jackson, 1997). Compare cross-bedding.
cross-slope bench Refer to terrace.
cross-stratification Arrangement of strata inclined at an angle to the main stratification. This is a general term having two subdivisions: cross-bedding, in which the cross-strata are thicker than 1 cm, and cross-lamination, in which they are thinner than 1 cm. A single group of related cross-strata is a set, and a group of similar, related sets is a coset ( Jackson, 1997).
crumb
(aggregate) A soft, porous, more or less rounded ped from 1 to 5 mm in diameter. (Not used in current U.S. soil pedology) Compare soil structure shapes and Table 2.
crumb structure A structural condition in which most of the peds are crumbs. (Not used in current U.S. system of soil taxonomy.) Compare soil structure shapes.
crushing Refer to tillage, crushing.
crushing strength The force required to crush a mass of dry soil, or, conversely, the resistance of the dry soil mass to crushing. Expressed in units of force per unit area (pressure).
crust A transient soil-surface layer, ranging in thickness from a few millimeters to a few centimeters, that is either denser, structurally different, or more cemented than the material immediately beneath it, resulting in greater soil strength when dry as measured by penetration resistance or other indices of soil strength. Crusts can be subdivided into biological crusts or mineralogical crusts (e.g., chemical crusts–evaporite crystals; or physical crusts (raindrop impact, depositional, freezethaw, or vesicular crusts; Schoeneberger, et al., 2002).
Cryalfs [soil taxonomy] A suborder of Alfisols that are cold and more or less well drained. Characteristically, Cryalfs have an O horizon, an albic horizon, and an argillic horizon. Nearly all of these soils have a cryic soil temperature regime and commonly have a udic moisture regime (USDA, 1999; Appendix I).
Cryands [soil taxonomy] A suborder of Andisols are cold and more or less well drained. Characteristically, Cryands have an ochric or melanic epipedon, and a thin O horizon and a cambic horizon. They have a cryic or pergelic soil temperature regime (USDA, 1999; Appendix I).
Cryepts [soil taxonomy] A suborder of Inceptisols that are cold, commonly of high mountains or high latitudes. They lack permafrost within 100 cm of the soil surface. Cryepts commonly have a thin, dark brownish ochric epipedon over a brownish cambic horizon; some have bedrock within 100 cm of the surface. They have a cryic soil temperature regime (USDA, 1999).
Cryerts [soil taxonomy] A suborder of Vertisols that are cold and more or less freely drained. These soils commonly have dark surface horizons, cracks that open and close, depending upon the amount of precipitation, and have a cryic soil temperature regime (USDA, 2004; Appendix I).
cryic A soil temperature regime that has mean annual soil temperatures of >0°C but <8°C, >5°C difference between mean summer and mean winter soil temperatures at 50 cm, and cold summer temperatures (USDA, 1999).
Cryids [soil taxonomy] A suborder of Aridisols of cold desert and high elevations and with short growing seasons. They may have a duripan or an argillic, calcic, cambic, gypsic, natric, petrocalcic, petrogypsic, or salic horizon. Cryids have a cryic soil temperature regime, and commonly exhibit periglacial features (USDA, 1999; Appendix IA).
Cryods [soil taxonomy] A suborder of cold Spodosols of high latitudes or high elevations. They commonly have an O horizon over a very thin or intermittent albic horizon, which overlies a well-developed spodic horizon. Some of the soils have a placic horizon, ortstein, or another cemented soil layer within 100 cm of the mineral soil surface. Cryods that have a cryic or pergelic soil temperature regime (USDA, 1999; Appendix I).
cryogenic soil Soil that has formed under the influence of cold soil temperatures.
Cryolls [soil taxonomy] A suborder of Mollisols that are cold and more or less freely drained. They have a mollic epipedon and a cryic soil temperature regime. Cryolls have a udic, ustic, or xeric moisture regime (USDA, 1999; Appendix I).
cryophile Synonym psychrophilic organism.
cryoplanation The reduction and modification of a land surface by processes associated with intensive frost action, such as solifluction, supplemented by the erosive and transport actions of running water, moving ice, and other agents ( Jackson, 1997).
cryoturbate A mass of soil or other unconsolidated earthy material moved or disturbed by frost action, and usually coarser than the underlying material; especially a rubbly deposit formed by solifluction ( Jackson, 1997).
cryoturbation A collective term used to describe all soil movements due to frost action, characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits (National Research Council of Canada, 1988). Compare pedoturbation.
cryptogamic crust A type of microbiotic crust consisting of a thin, biotic layer at the ground surface composed predominantly of cryptogams (i.e., algae, lichen, mosses, lichens and liverworts); most commonly found in semiarid or arid environments (Schoeneberger and Wysocki, personal communication, 2013; Summer and Stewart, 1992). Compare microbiotic crust.
crystal A regular arrangement of atoms in space.
crystal structure The orderly arrangement of atoms in a crystalline material.
crystallaria Single crystals, or arrangements of crystals of relatively pure fractions of the plasma that do not enclose the s-matrix of the soil material but form coherent masses; their morphology is consistent with their formation and present occurrence in original voids in the enclosing soil material.
crystalline rock A rock consisting of various minerals that have crystallized in place from magma. Crystalline rock have a well-ordered arrangement of ions, a definite chemical composition, and a regular geometrical form. Compare igneous rock and sedimentary rock.
cuesta An asymmetric ridge capped by resistant rock layers of slight to moderate dip, commonly less than 10° (approximately <15%); a homocline type produced by differential erosion of interbedded resistant and weak rocks. A cuesta has a long, gentle slope on one side (dip slope), that roughly parallels the inclined beds, and on the opposite side has a relatively short, steep or cliff-like slope (scarp slope) that cuts through the tilted rocks (Schoeneberger and Wysocki, personal communication, 2013; Hawley and Parsons, 1980). Compare hogback, homoclinal ridge, mesa, dipslope, scarp slope, cuesta valley.
cuesta valley An asymmetrical depression adjacent to a cuesta that lies parallel to the strike of the underlying strata; a type of strike valley. It’s formed by the differential erosion of weaker strata interbedded with, or stratigraphically adjacent to more resistant rocks. It may or may not contain a local drainage network but commonly lies above and is unconnected to the regional drainage system. Compare cuesta, strike valley (Schoeneberger and Wysocki, personal communication, 2013).
cultipack Refer to tillage, cultipack.
cultivation Refer to tillage, cultivation.
culture, microbiological A population of microorganisms cultivated in an artificial growth medium. A pure culture is grown from a single cell; a mixed culture consists of two or more microorganisms growing together.
cumulative infiltration Total volume of water infiltrated per unit area of soil surface during a specified time period. Contrast with infiltration flux (or rate).
cut [geology] A passage, incision, or space from which material has been excavated, such as a road cut or a railroad cut ( Jackson, 1997).
cut and fill A process of leveling, whereby material eroded from one place by waves, currents, streams, or winds is deposited nearby until the surfaces of erosion and deposition are continuous and uniformly graded; especially lateral erosion on the concave banks of a meandering stream accompanied by deposition within its loops. Compare flood-plain step, stream terrace, terrace ( Jackson, 1997).
cutan A modification of the texture, structure, or fabric at natural surfaces in soil materials due to concentration of particular soil constituents or in situ modification of the plasma.
cutback irrigation Refer to irrigation, cutback irrigation.
cutbank A slope or wall portion of a cut excavated into unconsolidated material (regolith) or bedrock, as in a borrow pit. It may stand nearly vertical resulting from collapse as the base is undercut during excavation or by erosion, or it may be reduced by subsequent erosion to a more subdued angle by slope wash (Schoeneberger and Wysocki, personal communication, 2013). Compare cut, beveled cut, roadcut.
cutoff [streams] The new and relatively short channel formed when a stream cuts through a narrow strip of land and thereby shortens the length of its channel ( Jackson, 1997).
cutter [karst] A dissolution groove or trench formed along vertical bedrock fractures beneath soil and usually buried beneath regolith with little or no ground surface expression, commonly wider than a solution fissure (widths commonly range from 0.5 to 3 m) and tapering down to a crack or a bedrock floored trench; also called grike (not preferred), or subsurface karren (Schoeneberger and Wysocki, personal communication, 2013; White, 1988). Compare karren, solution fissure, solution corridor.
cutting Refer to tillage, cutting.
cyclic salt Salt lifted by wind from the spray of sea water or salt lakes, blown inland, and returned to the originating water body via drainage.
cyclothem A series of beds deposited during a single sedimentary cycle of the type that prevailed during the Pennsylvanian Period. It is an informal, lithostratigraphic unit equivalent to “formation”. Cyclothems are typically associated with unstable shelf or interior basin conditions in which alternate marine transgression and regressions occur. The term has also been applied to rocks of different ages and of different lithologies from the Pennsylvanian cyclothems ( Jackson, 1997). Compare rhythmite.