ASTM D7099-04(2018)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7099 − 04 (Reapproved 2018)
Standard Terminology Relating to
Frozen Soil and Rock
This standard is issued under the fixed designation D7099; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope O., 1988,Glossary of Permafrost and Related Ground-Ice
Terms, Technical Memorandum,Associate Committee on
1.1 This terminology includes all of those terms which
Geotechnical Research, Ottawa, Canada
relate to frozen soils and rocks.
Everdingen, Robert van, ed., 1998, revised January,
1.2 It is based on: a list of definitions drawn up by ASTM
2002,Multi-Language Glossary of Permafrost and Re-
Sub-Committee D18.19;ASTM standards; a list of definitions
lated Ground-Ice Terms, National Snow and Ice Data
drawn up by the Canadian Geomorphology Research Group
Center/World Data Center for Glaciology, Boulder, Colo-
(CGRG); the Glossary of Permafrost and Related Ground-Ice
rado
Terms developed by the National Snow and Ice Data Center
NationalSnowandIceDataCenter,2003,EnglishLanguage
(NSIDC), at the University of Colorado, at Boulder; the Keys
Glossary of Permafrost and Related Ground-Ice Terms,
to Soil Taxonomy of the United States Department ofAgricul-
Boulder, Colorado, http://nsdic.org/fgdc/glossary/
ture (USDA); and contributions by a number of individuals.
english.html
1.3 For all of the terms included, the source is included in Natural Resources Conservation Service, United States De-
partment of Agriculture,Keys to Soil Taxonomy, Ninth
parentheses after the definition.
Edition, 2003, 331 pp., http://soils.usda.gov/technical/
1.4 This standard does not purport to address all of the
classication/tax_keys
safety concerns, if any, associated with its use. It is the
Permafrost Map of the USSR (1:2,500,000), 1996,Depart-
responsibility of the user of this standard to establish appro-
mentofGeocryology,MoscowStateUniversity,16sheets
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Significance and Use
1.5 This international standard was developed in accor-
3.1 This terminology can be used to find the definitions of
dance with internationally recognized principles on standard-
all of those terms which are used in association with frozen
ization established in the Decision on Principles for the
materials, including rocks, soils, and water.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Terminology
Barriers to Trade (TBT) Committee.
4.1 Definitions:
2. Referenced Documents
4.1.1 Allofthedefinitionsareconsistentwiththoselistedin
2.1 ASTM Standards:
Terminology D653.
D653Terminology Relating to Soil, Rock, and Contained active layer—the top layer of ground that is subject to annual
Fluids freezing and thawing. (In the zone of discontinuous
D4083Practice for Description of Frozen Soils (Visual- permafrost, the active layer is often underlain by unfrozen
Manual Procedure) ground.)
2.2 Other References:
active layer failure—any of several possible forms of slope
Harris, S. A., French, H. M., Heginbottom, J. A., Johnston,
failure in the active layer. NSIDC
G. H., Ladanyi, B., Sego, D. C., and van Everdingen, R.
active layer thickness—the thickness of the top layer of
This terminology is under the jurisdiction of ASTM Committee D18 on Soil ground that is subject to annual freezing and thawing.
and Rock and is the direct responsibility of Subcommittee D18.19 on Frozen Soils
NSIDC
and Rock.
CurrenteditionapprovedJuly1,2018.PublishedJuly2018.Originallyapproved
active rock glacier—a mass of rock fragments and finer
in 2004. Last previous edition approved in 2010 as D7099–04(2010). DOI:
material, on a slope, that contains an ice core or interstitial
10.1520/D7099-04R18.
2 ice,andwhichshowsevidenceofrecentmovement. NSIDC
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
adfreeze shear strength—the shear stress required to separate
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. two objects that are bonded together by ice.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7099 − 04 (2018)
adfreeze tensile strength—the tensile stress required to sepa- beaded stream—a characteristic pattern of small streams
rate two objects that are bonded together by ice. NSIDC underlain by ice wedges. “Beads,” or pools, occur at
junctions of wedges. The pools are linked by narrow
adfreezing—theprocessbywhichobjectsarebondedtogether
channels. NSIDC
by the ice formed between them. NSIDC
bottom temperature of snow cover—temperature measured
aggradation of permafrost—see permafrost aggradation.
at the base of the snow cover during mid- to late-winter
aggradational ice—newly formed ice lenses, especially in the (February/March). The measurements are used in the BTS
method to predict the presence or absence of permafrost.
lower part of the active layer, which become incorporated
intothepermafrostduetoaraisingofthepermafrosttableor NSIDC
a lowering of the permafrost base.
BTS method—a method to predict the presence or absence of
air freezing index—see freezing index. permafrost in a mountainous area, using measurements of
the bottom temperature of the snow in mid- to late-winter.
air thawing index—see thawing index.
NSIDC
albedo—the fraction of the total solar radiation incident on a
buried ice—ice formed on the ground surface and later
body that is reflected by it.
covered by sediments.
alpine permafrost—permafrost developed in temperate cli-
candled ice—ice that has rotted or otherwise formed, by
mate mountainous areas.
meltingduringthespring,intolongcolumnarcrystalswhich
altitudinal permafrost limit—the lowest altitude at which are very loosely bonded together. A distinctive “chiming”
mountainpermafrostoccursinahighlandareaoutsideofthe sound accompanies movement during “ice-out.”
general permafrost region. NSIDC
cave ice—ice formed in an open or closed cave. NSIDC
altitudinal permafrost zonation—the vertical subdivision of
clear ice—ice that is transparent and contains only a moderate
mountain permafrost into zones based on mean annual
number of air bubbles.
temperatures. NSIDC
closed-cavity ice—ice formed in a closed space, cavity, or
apparent heat capacity—the amount of heat required to raise
cave, in permafrost. NSIDC
the temperature of a unit mass of frozen ground by one
degree.ItisexpressedinJoulesperkgperdegreeK. NSIDC
closed-system freezing—freezingthatoccursunderconditions
thatprecludethegainorlossofwaterbythesystem. NSIDC
approximate freezing index—the cumulative number of
degree-days below 0°C for a given period, calculated from
closed-system pingo—a pingo formed by the doming of
the mean monthly temperatures for a given station without
frozen ground due to the freezing of injected water. The
making corrections for positive degree-days in the spring
water is provided by the expulsion of pore water during the
and fall. NSIDC
growth of permafrost. Closed-system pingos are found in
poorly-drained terrain in the continuous permafrost zone.
approximate thawing index—the cumulative number of
NSIDC
degree-days above 0°C for a given period, calculated from
the mean monthly temperatures for a given station without
closed talik—a body of unfrozen ground occupying a depres-
making corrections for negative degree-days in the spring
sion in the permafrost table below a lake or river. NSIDC
and fall.
cloudy ice—ice that is translucent or relatively opaque due to
artificial ground freezing—the process of freezing earth
the content of air or for other reasons, but which is
materials by artificial means.
essentially sound and nonpervious.
banded cryogenic fabric—a distinct soil morphology in
coefficient of compressibility—the change in volume per unit
whichsoilparticlesformsubhorizontallayersastheresultof
volume of a substance per unit increase in effective com-
freezing and thawing. NSIDC
pressive stress, under isothermal conditions. NSIDC
barrens—areas of discontinuous vegetation cover in the polar
collapse scar—thatpartofapeatlandwherethewhole,orpart,
semi-desert of the High Arctic. NSIDC
ofapeatplateauhasthawedandcollapsedtothelevelofthe
surroundingland.Collapsesscarsarenotdepressionsbutare
basal cryopeg—a layer of unfrozen ground, forming the basal
marked by vegetation different from the peatland that was
portion of permafrost, in which the temperature is perenni-
not underlain by permafrost. NSIDC
ally below 0°C (32°F). NSIDC
composite wedge—a wedge, containing both soil and ice, that
basal cryostructure—the structural characteristics of a frozen
deposit of boulders that is saturated with ice. NSIDC shows evidence of both primary and secondary filling.
NSIDC
basal-layered cryostructure—the structural characteristics of
a frozen layered deposit of gravel and boulders that is compressive strength—the load per unit area at which an
saturated with ice. NSIDC unconfined cylindrical specimen of soil or rock will fail in a
D7099 − 04 (2018)
simple compression test. Commonly the failure load is the cryogenic temperature—the term can apply to temperatures
maximum that the specimen can withstand in the test. D653 below−50°Cbutisusuallyusedforthosetemperaturesclose
to absolute zero (−273°C). NSIDC
conglomeric cryogenic fabric—a distinct soil micromorphol-
ogy resulting from the effects of freezing and thawing, in cryolithology—the study of the genesis, structure, and lithol-
which coarser soil particles form compound arrangements.
ogy of frozen earth materials. NSIDC
NSIDC
cryopedology—the study of soils at temperatures below 0°C.
construction methods in permafrost—special procedures of
cryopeg—alayerofunfrozengroundinwhichthetemperature
design and construction that are required when engineering
is perennially below 0°C. In general, the freezing of such
works are undertaken in areas of permafrost.
layers is prevented due to the depression of the freezing
contemporary permafrost—(1) newly formed permafrost in
point by solids dissolved in the pore water.
an area where surface temperatures have fallen below 0°C
cryoplanation—the process through which cryoplanation ter-
(32°F); (2)permafrostthatisinthermalequilibriumwiththe
races form. NSIDC
existing mean annual surface or sea-bottom temperature and
the geothermal heat flux.
cryoplanation terraces—hillside benches or table-like sum-
mitsurfaceswhicharethoughttohaveresultedfromintense
continuous permafrost—permafrost occurring everywhere
frost wedging associated with snowbanks.These are usually
beneath the exposed land surface throughout a geographic
underlain by permafrost and are considered by some as
region, with the exception of widely scattered sites, such as
diagnostic landforms of permafrost terrain. NSIDC
newly-deposited unconsolidated sediments, where the cli-
mate has just begun to impose its influence on the ground
cryosol—soilwithin1to2mofthesurfaceinwhichthemean
thermal regime and will cause the formation of continuous
annual ground temperature is below 0°C. NSIDC
permafrost.
cryosphere—that part of the Earth’s crust, hydrosphere, and
continuous permafrost zone—a major subdivision of a per-
atmosphere subject, for at least a part of each year, to
mafrost region, in which permafrost occurs everywhere
temperatures below 0°C (32°F). NSIDC
beneath the land surface, with the possible exception of
widely scattered sites; both in North American (GPRGIT) cryostructure—the structural characteristics of frozen earth
andinRussian(PermafrostMapoftheUSSR)usage:>80% materials. NSIDC
of area underlain by permafrost.
cryosuction—a suction which develops in freezing or
convection tube—a closed single-phase heat transfer device
partially-frozen fine-grained materials due to temperature-
that removes heat from the ground whenever conditions are dependent differences in unfrozen water content. NSIDC
appropriate to drive the internal convection cell.
cryotexture—the textural characteristics of frozen earth ma-
creep of frozen ground—the slow deformation that results
terials cemented together with ice. NSIDC
from long-term application of a stress too small to produce
cryotic ground—soil or rock in which the temperatures are
failure in the frozen material.
0°C, or below. NSIDC
creep strength—the failure strength of a material at a given
cryoturbate—a body of earth material moved or disturbed by
rate of strain or after a given period under deviatoric stress.
the action of frost. NSIDC
NSIDC
cryoturbation—(1) a collective term to describe all soil
crust-like cryostructure—thestructuralpropertiesofafrozen
movements due to frost action; (2) irregular structures
deposit of angular blocks that are coated with ice, while
formed in earth materials by deep frost penetration and frost
large spaces between the blocks are not filled with ice.
action processes. NSIDC
NSIDC
debris flow—a sudden and destructive form of landslide, in
cryofront—the boundary between frozen and unfrozen
which loose materials on a slope, with at least half of the
ground, as indicated by the position of the 0°C isotherm in
particles being larger than sand, are mobilized by saturation
the ground. NSIDC
and flow downwards. NSIDC
cryogenesis—the combination of thermophysical, physico-
deformability—the ability of a material to change its shape or
chemical, and physico-mechanical processes that occur in
size under the influence of an external or internal agency.
freezing, frozen, and thawing earth materials. NSIDC
NSIDC
cryogenic aquiclude—a frozen layer of ground with suffi-
ciently low permeability as to act as a confining bed for an degree-day—a unit of heat measurement equal to one degree
of the variation of the mean temperature for a day from a
aquifer. NSIDC
given reference (or, base) temperature.
cryogenic fabric—the distinct soil micromorphology which
results from the effects of freezing and thawing processes. degree of saturation—(1) the total degree of saturation of
NSIDC frozen soil is the ratio, expressed as a percentage, of the
D7099 − 04 (2018)
volume of ice and unfrozen water in the soil pores to the drunken forest—agroupoftreesleaninginrandomdirections
volume of the pores; (2) the degree of saturation of frozen in a permafrost region; usually associated with thermokarst
soil by ice, expressed as a percentage, is the ratio of the topography.
volume of ice in the soil pores to the volume of the pores.
dry density—the mass of a unit volume of dried material.
NSIDC
NSIDC
density of frozen ground—the ratio of mass per unit of
dry frozen ground—frozengroundwithaverylowtotalwater
volume of frozen earth materials.
content, consisting almost completely of interfacial water,
depth of seasonal frost penetration—themaximumthickness
and not cemented by ice. NSIDC
of the seasonally frozen layer. NSIDC
dry permafrost—perennially frozen soil or rock without ice,
depth of thaw—the distance from the ground surface down-
or with an ice content lower than the pore volume, so that it
ward to frozen ground at any time during the thaw season.
does not yield excess water on thawing.
depth of zero annual amplitude—the distance from the
dynamic modulus of elasticity—theratioofstresstostrainfor
groundsurfacedownwardtothepointbeneathwhichthereis
a material under dynamic loading conditions. NSIDC
virtually no annual fluctuation in the mean ground tempera-
ture.
dynamic Poisson’s ratio—the absolute value of the ratio
betweenthelinearstrainchanges,perpendiculartoandinthe
desiccation crack—a crack or fissure in fine-grained soil
directions of a given uniaxial stress change, respectively,
material resulting from shrinkage during drying. NSIDC
under dynamic loading conditions. NSIDC
desiccation polygon—a closed, multi-sided, pattern in the
ground formed by desiccation cracks in fine-grained soils.
earth hummock—a hummock having a core of silty and
NSIDC clayey mineral soil which may show evidence of
cryoturbation. NSIDC
design depth of frost penetration—(1) in North American
usage: the mean of the three largest depths of seasonal frost
electrical conductivity—the property of conducting electric-
penetration measured during the past thirty years, or, the
ity.
largest depth of seasonal frost penetration beneath a snow-
electrical properties of frozen ground—these include the:
free soil surface measured during the past ten years; (2) in
dielectric constant, electrical conductivity, and electrical
Russian usage: the mean of the depths of seasonal frost
resistivity.
penetration during at least the last ten years with the ground
surface free of snow and the groundwater level beneath the
electrical resistivity—the property of a material that deter-
depth of seasonal frost penetration. NSIDC
mines the electrical current flowing through a centimeter
detachment failure—a slope failure in which the thawed or
cubeofthematerialwhenanelectricalpotentialisappliedto
thawingpartoftheactivelayerdetachesfromtheunderlying
the opposite faces of the cube. NSIDC
frozen material. NSIDC
epigenetic ice—ice in the ground that formed after the
dielectric constant—a measure of the ability of a material to
deposition of the earth material in which it occurs.
store electrical energy in the presence of an electrostatic
field. epigenetic ice wedge—an ice wedge that developed after the
deposition of the earth material in which it occurs.
dilation crack—a tensile fracture in a frozen material caused
by surface extension due to doming, slope or embankment
epigenetic permafrost—(1) permafrost that formed after the
movement, or toppling.
deposition of the earth material in which it occurs; (2)
permafrost that formed through the lowering of the perma-
dilation crack ice—ice that forms in dilation cracks. NSIDC
frost base in previously deposited material. NSIDC
discontinuous permafrost—permafrost occurring in some
equilibrium permafrost—permafrost that is in equilibrium
areas beneath the ground surface throughout a geographic
with the existing mean annual surface or sea-bottom tem-
region where other areas are free of permafrost.
perature and with the geothermal heat flux. NSIDC
discontinuous permafrost zone—a major subdivision of a
permafrost region in which permafrost occurs in some areas
excess ice—theiceinthegroundthatexceedsthetotalvolume
beneath the ground surface while other areas are free of
of the pores that the ground would have under natural
permafrost; (1)inNorthAmericanusage:30to80%ofarea
unfrozen conditions.
underlain by permafrost; (2) in Russian usage: 3 to 80% of
fabric—the micromorphology of soil.
area underlain by permafrost. GPRGIT; Permafrost Map
of the USSR, 1996
fragmic cryogenic fabric—a distinct soil micromorphology,
disequilibrium permafrost—permafrost that is not in thermal resulting from processes of freezing and thawing, in which
equilibrium with the existing mean annual surface or sea- soil particles form discrete units that are densely packed.
bottom temperature and the geothermal heat flux. NSIDC NSIDC
D7099 − 04 (2018)
fragmoidal cryogenic fabric—a distinct soil frost cracking—fracturing of the ground by thermal contrac-
micromorphology, resulting from the processes of freezing tion at temperatures below 0°C (32°F).
and thawing, in which soil particles form discrete units that
frost creep—thenetdownslopedisplacementthatoccurswhen
are coalescing. NSIDC
a soil, during a freeze-thaw cycle, expands normal to the
frazil ice—crystalsoficethatforminturbulentstreamsincold
ground surface and settles in a nearly vertical direction.
weather.
NSIDC
free water—that portion of the pore water that is free to move
frost heave (heaving)—the upward or outward movement of
between interconnected pores under the influence of gravity.
the ground surface (or objects on, or in the ground), caused
NSIDC
by the formation of ice in the soil. NSIDC
freeze-thaw cycle—the freezing of a material followed by
frost-heave extent—the difference between the elevations of
thawing.
the ground surface before and after the occurrence of frost
freezeback—refreezing of thawed materials. NSIDC heave. NSIDC
freezing (of ground)—thechangingofphasefromwatertoice
frost jacking—the cumulative upward or outward displace-
in soil or rock. NSIDC
ment of slabs or blocks of rock, or of objects embedded in
the ground, due to repetitive freezing and thawing.
freezing front—the advancing boundary between frozen (or
partially frozen) and unfrozen ground. NSIDC
frost mound—any mound-shaped landform produced by
ground freezing combined with accumulation of ground ice
freezing index—(1) the cumulative number of degree-days
due to groundwater movement or the migration of soil
below0°Cforagivenperiod; (2)thenumberofdegree-days
moisture. NSIDC
between0°C(32°F)andthemeantemperatureeachday.The
index is determined from temperatures measured about 1.4
frost penetration—themovementofthefreezingfrontintothe
m (4.5 ft) above the ground surface. That determined from
ground during freezing. NSIDC
temperaturesmeasuredat,orimmediatelybelow,asurfaceis
known as the surface freezing index.
frost phenomena—the effects on earth material and structures
resulting from frost action. NSIDC
freezing point—(1) the temperature at which a pure liquid
solidifies under atmospheric pressure; (2) the temperature at
frost shattering—the mechanical disintegration of rock
which a ground material starts to freeze. NSIDC
caused by the pressure of the freezing of water in pores and
along grain boundaries. NSIDC
freezing-point depression—the number of degrees by which
the freezing point of an earth material is depressed below
frost sorting—the differential movement of soil particles of
0°C (32°F).
different size ranges as a result of frost action. NSIDC
freezing pressure—the positive pressure developed at ice-
frost-stable ground—soil or rock in which little or no segre-
water interfaces in a soil as it freezes. NSIDC
gated ice forms during seasonal freezing. NSIDC
friable—a condition under which the material is easily broken
frost-susceptible ground—soil or rock in which segregated
up under light to moderate pressure.
ice will form, causing frost heave, under the required
friable permafrost—permafrostinwhichthesoilparticlesare
conditions of moisture supply and temperature. NSIDC
not held together by ice. NSIDC
frost weathering—the disintegration and break-up of soil or
frost—the occurrence of air temperatures below 0°C. NSIDC
rock by the combined action of frost shattering, frost
wedging, and hydration shattering. NSIDC
frost action—the process of alternate freezing and thawing of
moisture in soil, rock, and other materials, and the resulting
frost wedging—the mechanical disintegration, splitting, or
effects on materials and on structures placed on, or in, the
breaking-upofrockcausedbythepressureofthefreezingof
ground.
water in cracks, crevices, pores, joint, or bedding planes.
frost blister—a seasonal frost mound produced through dom-
NSIDC
ing of seasonally frozen ground through a subsurface accu-
frozen fringe—the zone in a freezing, frost-susceptible soil
mulation of water under elevated hydraulic potential during
between the warmest isotherm at which ice exists in pores
progressive freezing of the active layer. The areas affected
and the isotherm at which the warmest ice lens is growing.
can be quite large. NSIDC
frozen ground—soil or rock in which all or part of the pore
frost boil—a small mound of soil material, presumed to have
water has turned into ice. NSIDC
been formed through frost action. NSIDC
frost bulb—amore-or-lesssymmetricalzoneoffrozenground gas hydrate—a special form of a solid lattice-like structure in
formed around a buried chilled pipeline, or beneath or which crystal lattice cages or chambers consisting of host
around a structure maintained at temperatures below 0°C molecules (water) enclose guest molecules (of a variety of
(32°F). gases). NSIDC
D7099 − 04 (2018)
gelifluction—the slow downslope flow of unfrozen earth histel—a suborder of gelisol that contains large quantities of
materials on a frozen substrate. NSIDC organic matter. USDA
gelisol—perennially frozen soil that contain permafrost within hydraulic conductivity—the volume of fluid passing through
a unit cross section in unit time under the action of a unit
2 m of the surface. USDA
hydraulic potential gradient. It is commonly expressed in
geocryology—the study of earth materials having a tempera-
cm/second or m/day. NSIDC
ture below 0°C (32°F).
hydraulic diffusivity—the ratio of the hydraulic conductivity
geothermal gradient—the rate of temperature increase with
and the storage capacity of a groundwater aquifer. NSIDC
depth in the earth.
hydraulic thawing—artificial thawing and removal of frozen
geothermal heat flux—the amount of heat moving steadily
ground by the use of a stream or jet of water under high
outward from the interior of the earth through a unit area in
pressure. NSIDC
unit time. NSIDC
hydrochemical talik—a layer or body of unfrozen ground, at
glacial till (till)—material left after the retreat of glaciers and
a temperature of less than 0°C, in a permafrost area, which
ice sheets, usually composed of a wide range of particle
remains unfrozen due to moving mineralized groundwater.
sizes, which has not been subjected to the sorting action of
NSIDC
water. D653
hydrothermal talik—a layer or body of unfrozen ground, at a
glaciolacustrine deposits—glaciofluvial deposits that settled temperature above 0°C, in an area of permafrost, which is
in standing water.
maintained by moving groundwater. NSIDC
granic cryogenic fabric—a distinct soil micromorphology, ice—water in the frozen, solid, state.
resulting from the processes of freezing and thawing, in
ice-bearing permafrost—permafrost that contains ice.
which soil particles form discrete loosely packed units.
NSIDC
NSIDC
ice-bonded permafrost—ice-bearing permafrost in which the
granoidic cryogenic fabric—adistinctsoilmicromorphology,
soil particles are cemented together by ice. NSIDC
resulting from the processes of freezing and thawing, in
which soil particles form more-or-less discrete loosely ice, candled—see candled ice.
packed units. NSIDC
ice content—(1) the ratio, expressed as a percentage, of the
weightoftheicephasetotheweightofdrysoil; (2)theratio,
granular ice—ice that is composed of coarse, more-or-less
expressed as a fraction, of the volume of ice in a sample to
equi-dimensional, crystals that are weakly bonded together.
the volume of the whole sample. In the volumetric calcula-
gravimetric (total) water content—the ratio, expressed as a
tion the ratio cannot exceed unity. In the gravimetric
percentage, of the mass of the water and ice in a sample to
calculation, the percentage can exceed 100%. NSIDC
the dry mass of the sample. NSIDC
ice-cored topography—topography that is due almost solely
ground ice—(1)iceinpores,cavities,voids,orotheropenings
to differences in the amount of excess ice underlying the
in soil or rock, including massive ice; (2) a general term
surface. NSIDC
referring to all types of ice in freezing and frozen ground.
ice crystal—a very small individual crystal or particle of ice
NSIDC
visible in, or on, the face of a mass of soil or rock. Crystals
ground settlement—downward movement of the ground
may occur alone, or in combination with other ice forma-
causing a lowering of the ground surface resulting from the
tions.
melting of ground ice in excess of that contained in pore
ice, epigenetic—see epigenetic ice.
fillings.
ice, excess—see excess ice.
hard frozen ground—frozen soil or rock which is firmly
cemented by ice. NSIDC
ice, frazil—see frazil ice.
heat capacity—the amount of heat required to raise the
ice lens—a lens-shaped body of ice ranging in thickness from
temperature of a unit mass of a substance by one degree. It
hairlineto0.3m.Icelayersmorethan0.3minthicknessare
is commonly expressed in Joules per kg per degree K.
better termed massive ice beds.
NSIDC
ice lenses—lenticular formations of ice in soil occurring
heaving pressure—upward pressure developed during freez-
essentially parallel to each other, generally normal to the
ing of the ground. NSIDC direction of heat loss, and commonly in repeated layers.
high-center polygon—anice-wedgepolygoninwhichmelting ice nucleation temperature—the temperature at which ice
of the surrounding ice wedges has left the center in a first forms during freezing of a soil/water system that does
relatively elevated position. NSIDC not initially contain ice. NSIDC
D7099 − 04 (2018)
ice-rich permafrost—perennially frozen ground that contains which soil particles form subhorizontal layers of similar
ice in excess of that required to fill pore spaces. thickness. NSIDC
ice segregation—theprocessofformationofsegregatediceby isolated cryopeg—a body of unfrozen ground, in which the
freezing of water in mineral or organic soil.
temperature is perennially below 0°C, and which is entirely
surrounded by perennially frozen ground. NSIDC
ice vein—an ice-filled crack or fissure in the ground. NSIDC
isolated talik—a layer or body of unfrozen ground entirely
ice wedge—a massive, wedge-shaped body of ice in soil,
surrounded by perennially frozen ground. NSIDC
usually with its apex pointing downwards, and composed of
foliated, or layered, vertically-orientated (commonly white)
isotherm—alineonachartthatconnectsallpointsofequalor
ice. Wedges may be as much as several metres wide at the
constant temperature.
top, and penetrate the soil to a feather edge at depths of
kurum (Russian)—a general term for all types of coarse
several metres.These may be “active”or“inactive” depend-
formations of broken rocks, on slopes of up to 40°, moving
ingonwhetherornotthesearegrowingbyrepeated,butnot
downslope mainly due to creep. NSIDC
necessarily annual, winter cracking.
lake talik—a layer or body of unfrozen ground occupying a
ice wedge cast—a filling of soil or sediment into the space
depression in the permafrost table beneath a lake. NSIDC
formerly occupied by an ice wedge.
latent heat of fusion—the amount of heat required to melt all
ice wedge polygon—any polygon surrounded by troughs
the ice (or freeze all of the pore water) in a unit mass of soil
underlain by ice wedges.
or rock. NSIDC
iciness—a qualitative term describing the quantity of ice in
frozen ground. NSIDC lateral talik—alayerorbodyofunfrozengroundoverlainand
underlain by perennially frozen ground. NSIDC
icing—a sheet-like mass of layered ice, formed either on the
ground surface or on the surface of river or lake ice, by latitudinal limit of permafrost—the southernmost latitude at
freezingofsuccessiveflowsofwaterthatmayseepfromthe which permafrost occurs in a lowland region of the northern
ground, flow from a spring or emerge from below river or
hemisphere, or the northernmost latitude for the same in the
lake ice through fractures. (aufeis, German; naled, Russian) southern hemisphere. NSIDC
icing blister—a seasonal frost mound consisting of ice only
latitudinal zonation of permafrost—the subdivision of a
and formed at least in part through lifting of one or more
permafrost region into permafrost zones, based on the
layers of icing by injected water. NSIDC
percentage of the area that is underlain by permafrost.
NSIDC
icing glade—an area which remains free of trees and shrubs
due to annual occurrences of icings. NSIDC
layered cryostructure—the cryostructure of frozen silt or
loam in which ice layers alternate with mineral layers that
icing mound—a seasonal frost mound consisting exclusively
have a massive cryostructure. NSIDC
of thinly-layered ice, which has been formed by the freezing
of successive flows of water. NSIDC
lens ice—ground ice occurring as lenses. NSIDC
inactive ice wedge—an ice wedge that is no longer growing.
lens-type cryostructure—the cryostructure of frozen silt or
NSIDC
loam containing numerous ice lenses. NSIDC
inactive rock glacier—a mass of rock fragments and finer
loess—a buff-colored wind-blown deposit of fine silt.
material on a slope that contains either an ice core or
long-term strength—the failure strength of a material after a
interstitial ice, and which shows evidence of past, but not
long period of creep deformation. NSIDC
present, movement. NSIDC
infiltration (of soil)—movement of water from the ground low-center polygon—an ice wedge polygon in which thawing
of ice-rich permafrost has left the central area in a relatively
surface into soil.
depressed condition. NSIDC
in-situ—in its original place or environment.
macro-scale polygons—closed, multi-sided, roughly equi-
interfacial water—water in transition layers at mineral/water
dimensional, patterned ground features, commonly resulting
and mineral/water/ice interfaces in frozen ground. NSIDC
from cracking of the ground due to thermal contraction.
NSIDC
intrapermafrost water—water occurring in unfrozen zones
(that is, taliks and cryopegs) within permafrost. NSIDC
marine cryopeg—a layer or body of unfrozen ground, in
intrusive ice—ice formed from water intruded or injected which the temperature is perennially below 0°C, which
forms part of coastal or sub-sea permafrost. NSIDC
under pressure into soils and rocks.
isoband cryogenic fabric—a distinct soil micromorphology, mass wasting—downslope movement of soil or rock, on or
resulting from the processes of freezing and thawing, in near the ground surface, due to gravity.
D7099 − 04 (2018)
massive-agglomerate cryostructure—the cryostructure of needle ice—thin, elongated, crystals of ice that form perpen-
frozen silt or loam in which ice veins form an irregular dicular to the surface of the ground. NSIDC
three-dimensional network. NSIDC
noncryotic ground—geological materials at temperatures
above 0°C. NSIDC
massive cryostructure—the cryostructure of frozen ground in
which all of the mineral particles are bonded together with
non-frost-susceptible soil—a soil that does not display sig-
ice.
nificant detrimental ice segregation during freezing.
massive ice—a comprehensive term used to describe large
nonsorted circle—a form of patterned ground that is equi-
masses(atleast10to100cm)ofundergroundice,including
dimensional in several directions with a dominantly circular
ice wedges, pingo ice, buried ice and dominantly horizontal
outline which lacks a border of stones. NSIDC
icebeds.Massiveicebedstypicallyhaveanicecontentofat
least 250% (on an ice-to-dry-soil weight basis). If the ice
nonsorted net—a type of patterned ground with cells that are
content is less than 250%, the beds are better termed
equi-dimensional in several directions, but neither circular
“massive icy beds.” Massive ice beds have a minimum
nor polygonal, and lacking borders of stones. NSIDC
thickness of 0.3 m. Some massive ice beds are more than 40
nonsorted polygon—a type of patterned ground that is equi-
m thick and several kilometres in horizontal extent. Ice beds
dimensionalinseveraldirections,withadominantpolygonal
less than 0.3 m thick are better termed ice lenses.
outline, and lacking a border of stones. NSIDC
massive-porous cryostructure—the cryostructure of frozen
nonsorted step—a type of patterned ground with a step-like
sand and gravel in which all of the mineral particles and
form and a downslope border of vegetation embanking an
bondertogetherwithice,butinwhichlargerporespacesare
area of relatively bare ground upslope. NSIDC
not completely filled with ice. NSIDC
nonsorted stripe—a type of patterned ground with a striped
mean annual ground surface temperature—themeanannual
and nonsorted appearance, which is due to parallel strips of
temperature of the surface of the ground. NSIDC
vegetation-covered ground and intervening strips of rela-
mean annual ground temperature—the mean annual tem- tively bare ground, and orientated down the steepest avail-
perature of the ground at a particular depth. NSIDC able slope. NSIDC
mechanical properties of frozen ground—these include the onshore permafrost—permafrost beneath exposed land
static and dynamic properties relating to the strength and
surfaces. NSIDC
deformability of frozen geological materials: the compres-
open-cavity ice—ice formed in an open cavity or crack in the
sive and shearing strengths, with and without confinement;
ground by reverse sublimation of water vapor. NSIDC
the static and dynamicYoung’Modulus and Poisson’s ratio;
the velocities of compressional and shear waves; seismic
open-system freezing—freezing that occurs under conditions
velocities.
in which water can be gained or lost by the system. NSIDC
mechanical strength—the failure strength of a material under
open-system pingo—a pingo formed by doming of frozen
given loading conditions. NSIDC
ground due to the freezing of injected water supplied by
groundwater moving downslope through taliks to the site of
micro-scale polygon—closed, multi-sided, roughly equi-
the pingo, where it move to the surface. NSIDC
dimensional, pattern ground usually caused by desiccation
cracking of fine-grained soils. The polygons are less than 2
open talik—a body of unfrozen ground that penetrates the
m in diameter. NSIDC
permafrost completely.
minerogenic palsa—a palsa in which the core extends below
orbicular cryogenic fabric—a distinct soil micromorphology
the peat into the underlying material. NSIDC
resulting from the effects of freezing and thawing, in which
coarser soil particles form circular to ellipsoidal patterns.
mountain permafrost—permafrost existing at high altitudes,
NSIDC
regardless of latitude.
organic cryosol—an organic soil having a surface layer
mud circle—a type of nonsorted circle developed in fine-
containing more than 17% organic carbon by weight, with
grained materials. NSIDC
permafrost within 1 m below the surface. NSIDC
multiple retrogressive slide—a type of mass movement
oriented lake—one of a group of lakes possessing a common,
associated with shear failure in unfrozen sediments under-
preferred, long-axis orientation. NSIDC
lying permafrost, leading to detachment of blocks of frozen
groundthatmovedownslope.Thistypeofslideisnotunique
orthel—a suborder of gelisol that contains neither large
to frozen geological materials and may also occur in quantities of organic matter (as in histels), nor evidence of
non-permafrost conditions. NSIDC extensive mixing due to frost action (as in turbels). USDA
n-factor—the ratio of the surface freezing or thawing index to paleosol—an ancient soil or soil horizon that formed on the
the air freezing or thawing index. NSIDC earth’s surface during the geologic past.
D7099 − 04 (2018)
palsa—a peaty permafrost mound possessing a core of alter- periglacial processes—processes associated with frost action
nating layers of segregated ice and peat or mineral soil in cold, non-glacial environments. NSIDC
material. NSIDC
permacrete—an artificial mixture of frozen soil materials
palsa bog—a poorly-drained lowland underlain by organic- cementedbyporeice,whichformsaconcrete-likeconstruc-
rich sediments, which contains perennially frozen peat tion material for use in cold regions. NSIDC
bodies (peat plateaux) and occasionally palsas. NSIDC
permafrost—the thermal condition in which the temperatures
partially-bonded permafrost—ice-bearing permafrost in in earth materials remain below 0°C (32°F) for at least two
which some of the soil particles are not bonded together by consecutivewintersandtheinterveningsummer;moisturein
ice. NSIDC theformofwaterandgroundicemayormaynotbepresent.
passive construction methods in permafrost—methods of permafrost aggradation—an increase in the thickness and/or
construction through which the foundation materials are area of permafrost through natural or artificial causes as a
maintained in the frozen state. resultofclimaticcoolingand/orchangeofterrainconditions
such as vegetation succession, filling of lake basins, or
passive single-phase thermal pile—a foundation pile pro-
human activity.
vided with a single-phase natural convection cooling system
to remove heat from the ground. NSIDC permafrost base—the lower boundary surface of permafrost,
above which temperatures are below 0°C (32°F), and below
passive two-phase thermal pile—a foundation pile provided
which temperatures are above 0°C (32°F).
with a two-phase natural convection cooling system to
remove heat from the ground. NSIDC permafrost boundary—(1) the geographical boundary be-
tween the continuous and discontinuous permafrost zones;
patterned ground—a general term for any ground surface
(2) the margin of a discrete body of permafrost. NSIDC
exhibiting a discernibly ordered, more or less symmetrical,
structural pattern of ground and, where present, vegetation. permafrost degradation—adecreaseinthicknessand/orareal
NSIDC extentofpermafrostbecauseofnaturalorartificialcausesas
a result of climatic warming and/or change of terrain
peat—an unconsolidated, compressible soil consisting of par-
conditions such as disturbance or removal of an insulating
tially decomposed semi-carbonized remains of plants, some
vegetation layer by fire or human means.
animals, and soil material. Peat, found in ancient bogs, can
permafrost limit—the geographical distal (terminal) boundar-
be the first stage in the formation of coal.
ies of the circumpolar, or alpine, or altitudinal, continuous
peat hummock—a hummock consisting of peat. NSIDC
and discontinuous permafrost zones.
peat plateau—a generally flat-topped, expanses of peat rising
permafrost region—a region in which the temperature of
one or more meters above the general surface of a peatland
some or all of the ground beneath the layer which freezes
(or, peat bog). In a peat plateau, a layer of permafrost exists.
and thaws seasonally remains at or below 0°C for at least
This may penetrate into the peat below and farther, into the
two consecutive years.
underlying mineral soil.
permafrost, relict—see relict permafrost.
peatland—peat-covered terrain.
permafrost, saline—see saline permafrost.
percolation—the movement of water downward and radially
through subsurface soil layers. permafrost table—the upper boundary surface of permafrost.
pereletok (Russian)—a layer of frozen ground which forms permafrost thickness—the vertical distance between the per-
part of the seasonally frozen ground, in areas either free of mafrost table and the permafrost base.
permafrost or with a lowered permafrost table, which re-
permafrost zone—amajorsubdivisionofapermafrostregion.
mains frozen through one or several summers, and then
NSIDC
thaws. NSIDC
pingo—a perennial frost mound consisting of a core of
perennially frozen ground—see permafrost.
massive ice, produced primarily by injection of water, and
pergelic soil temperature regime—in United States Depart- covered with soil and vegetation. NSIDC
ment ofAgriculture (USDA) classification, these are soils in
pingo ice—massive ice which forms the core of a pingo.
which the mean annual temperature is less than 0°C (32°F).
NSIDC
Ice wedges and lenses are normal in such soils in the United
States. pingo remnant—a collapsed pingo. NSIDC
periglacial—the conditions, processes, and landforms associ- pingo scar—a pingo remnant in a contemporary non-
ated with cold non-glacial environments. NSIDC permafrost environment. NSIDC
periglacial phenomena—landforms and soil characteristics planetary permafrost—permafrost occurring on any of the
produced by periglacial processes. NSIDC planetary bodies.
D7099 − 04 (2018)
plastic frozen ground—fine-grained soil in which only a residual stress—the effective stress generated in a thawing
portion of the pore water has turned into ice. NSIDC soil if no change of volume is permitted during the thaw.
NSIDC
Poisson’s ratio—theabsolutevalueoftheratiobetweenlinear
strain changes, perpendicular to and in the direction of a residual thaw layer—a layer of thawed or unfrozen ground
given uniaxial stress change, respectively. NSIDC between seasonally frozen ground and the permafrost table.
polygon—a type pf patterned ground consisting of a closed, reticulate-blocky cryostructure—the
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