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the boundary between cryotic and noncryotic ground as indicated by the position of the 0 degrees Celsius isotherm in the ground.


the combination of thermophysical, physico-chemical and physico-mechanical processes occurring in freezing, frozen and thawing earth materials.

cryogenic aquiclude

a layer of ground which, because of its frozen state, has a low enough permeability to act as a confining bed for an aquifer.

cryogenic fabric

the distinct soil micromorphology resulting from the effects of freezing and thawing processes.

cryogenic temperature

in international materials science, this term refers to temperatures generally below -50 degrees Celsius, but usually to temperatures within a few degrees of absolute zero (-273 degrees Celsius).


the study of the genesis, structure and lithology of frozen earth materials.


the study of soils at temperatures below 0 degrees Celsius, with particular reference to soils subject to intensive frost action, and to soils overlying permafrost.


a layer of unfrozen ground that is perennially cryotic (forming part of the permafrost), in which freezing is prevented by freezing-point depression due to the dissolved-solids content of the pore water.


the process through which cryoplanation terraces form.

cryoplanation terrace

a step-like or table-like bench cut in bedrock in cold climate regions.


soil formed in either mineral or organic materials having permafrost either within 1 meter (3.3 feet) below the surface or, if the soil is strongly cryoturbated, within 2 meters (6.6 feet) below the surface, and having a mean annual ground temperature below 0 degrees Celsius.


one of the earth's spheres of irregular form existing in the zone of interaction of the atmosphere, hydrosphere and lithosphere, distinguished by negative or zero temperature and the presence of water in the solid or super-cooled state; the term refers collectively to the portions of the earth where water is in solid form, including snow cover, floating ice, glaciers, ice caps, ice sheets, seasonally frozen ground and perennially frozen ground (permafrost).


the structural characteristics of frozen earth materials.


a suction developed in freezing or partially frozen fine-grained materials as a result of temperature-dependent differences in unfrozen water content.


the textural characteristics of frozen, fine-grained organic and mineral earth materials cemented together with ice.

cryotic ground

soil or rock at temperatures of 0 degrees Celsius or lower.


a body of earth material moved or disturbed by frost action.


(1) (singular) a collective term used to describe all soil movements due to frost action (2) (plural) irregular structures formed in earth materials by deep frost penetration and frost action processes, and characterized by folded, broken and dislocated beds and lenses of unconsolidated deposits, included organic horizons and even bedrock.


like cumulus; generally descriptive of all clouds; vertical development in the form of rising mounds, domes or towers; driven by thermal convection and have vertical velocities greater than 1 meter (3.3 feet) per second.


a principal cloud type (cloud genus) of vertical development, exceptionally dense and vertically developed clouds, occurring either as isolated clouds or as a line or wall of clouds with separated upper portions; these clouds appear as mountains or huge towers, at least a part of the upper portions of which are usually smooth, fibrous, or striated, and almost flattened; this part often spreads out in the form of an anvil (incus) or vast plume; under the base of cumulonimbus, which is very dark, there frequently exist virga, precipitation, and low, ragged clouds, either merged with it or not; its precipitation is often heavy and always of a showery nature.


a principal low-level cloud type (cloud genus) in the form of individual, detached elements which are generally dense and possess sharp non-fibrous outlines; these elements develop vertically, appearing as rising mounds, domes, or towers, the upper parts of which often resembles a cauliflower; the sunlit parts of these clouds are mostly brilliant white; their bases are relatively dark and nearly horizontal; near the horizon the vertical development of cumulus often causes the individual clouds to appear merged; if precipitation occurs, it is usually of a showery nature.


process of initiation or intensification of a cyclonic circulation in the atmosphere; the opposite to cyclolysis.


process of weakening or terminating of a cyclonic circulation in the atmosphere; the opposite of cyclogenesis.


area in the atmosphere in which the pressures are lower than those of the surrounding region at the same level; it is represented on a synoptic chart by a system of isobars at a specified altitude level (or a system of contours at a specified pressure level) which enclose relatively low values of pressure (or altitude); a cyclone begins when a wave (young) cyclone forms and moves along a front; a mature cyclone has well-developed warm sectors and both cold and warm fronts; an occluded cyclone is that within which there has developed an occluded front.

cyclone ciruculation

atmospheric circulation associated with a cyclone (depression, low pressure area); it is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

cyclone movement

the spatial displacement of a center of low pressure caused by the local redistribution of mass in the atmosphere; the trajectory of the center is often altered by heating or cooling on the air column, which can result from thermal fluxes at the surface or latent heat transformations associated with cloud formation and precipitation; these processes change the temperature distribution in the air column, resulting in density changes which modify the surface pressures.

data analysis

Provides the user the ability to calculate or compare data parameters.


the removal of ice accumulation on aircraft, ships and other objects by mechanical, thermal or chemical devices.

dead ice

any part of a glacier which has ceased to flow; dead ice is usually covered with moraine.

debris flow

a sudden and destructive variety of landslide, in which loose material on a slope, with more than 50% of particles larger than sand size, is mobilized by saturation and flows down a channel or canyon.


the ability of a material to change its shape or size under the influence of an external or internal agency, such as stress, temperature, or pore pressure.

degree of saturation

(1) the total degree of saturation of frozen soil is the ratio of the volume of ice and unfrozen water in the soil pores to the volume of the pores (2) the degree of saturation of frozen soil by ice is the ratio of the volume of ice in the soil pores to the volume of the pores.

degree-day (C or F)

a derived unit of measurement used to express the departure of the mean temperature for a day from a given reference (or base) temperature.

delayed strength

the failure strength of a material at a given strain rate or after a given period under deviatoric stress.


hexagonal ice crystals with complex and often fernlike branches.

density of frozen ground

the mass of a unit volume of frozen soil or rock.