Cryoturbation by Brentwood Higman & Andrew Mattox

gelisols Gelisols are an order in USDA soil taxonomy. They are soils of very cold climates which are defined as containing permafrost within two meters of the soil surface. The word "Gelisol" comes from the Latin ''gelare'' meaning "to freeze", a referen ...

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permafrost Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

s), cryoturbation (frost churning) refers to the mixing of materials from various horizons of the soil down to the

bedrock In geology, bedrock is solid Rock (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

due to freezing and thawing. Cryoturbation occurs to varying degrees in most gelisols. The cause of cryoturbation lies in the way in which the repeated freezing of the soil during autumn causes the formation of

ice wedge An ice wedge is a crack in the ground formed by a narrow or thin piece of ice that measures up to 3–4 meters in length at ground level and extends downwards into the ground up to several meters. During the winter months, the water in the gr ...

s at the most easily erodible parts of the parent rock. If the parent rock is hard, this can cause quite deep erosion of the rock over many years. As this process continues, during the summer when an

active layer In environments containing permafrost, the active layer is the top layer of soil that thaws during the summer and freezes again during the autumn. In all climates, whether they contain permafrost or not, the temperature in the lower levels of the ...

forms in the soil this eroded material can easily move both from the soil surface downward and from the permafrost table upward. As this process occurs, the upper soil material gradually dries out (because the soil moisture moves from the warm surface layer to the colder layer at the top of the permafrost) so that it forms a granular structure with many very distinctive crystalline shapes (such as

ice lens Ice lenses are bodies of ice formed when moisture, diffused within soil or rock, accumulates in a localized zone. The ice initially accumulates within small collocated pores or pre-existing crack, and, as long as the conditions remain favorable, ...

es). Separation of coarse from fine soil materials produces distinctive patterned ground with different types of soil. The extent of cryoturbation in gelisols varies considerably: it occurs much more on exposed sites (where turbels dominate everywhere) than in sheltered sites such as valleys (where orthels are not significantly affected by cryoturbation form).

References

Gelisols
at

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

Glossary cryoturbation
at The

National Snow and Ice Data Center The National Snow and Ice Data Center (NSIDC) is a United States information and referral center in support of polar and cryospheric research. NSIDC archives and distributes digital and analog snow and ice data and also maintains information abo ...

University of Colorado The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: University of Colorado Boulder, University of Colorado Colorado Springs, University of Colorado Denver, and the University of Co ...

{{periglacial environment Pedology Permafrost

See also

References