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Gelisols are an order in USDA soil taxonomy. They are soils of very cold climates which are defined as containing permafrost within two meters (6 ft 7 in) of the soil surface. The word "Gelisol" comes from the Latin gelare meaning "to freeze", a reference to the process of cryoturbation that occurs from the alternating thawing and freezing ...
USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters (most commonly their properties) and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.
However, some ground-water gley soils have permeable lower horizons, including, for example, some sands in hollows within sand dune systems (known as slacks), and in some alluvial situations. Groundwater gleysoils develop where drainage is poor because the water table ( phreatic surface) is high, whilst surface-water gleying occurs when ...
In the US, Gelisols occur only in parts of Alaska; they are characterized by having permafrost within 100 cm of the surface. Histosols are organic soils lacking permafrost within 100 cm of the surface; they are characteristically formed on wet sites, e.g. bogs, some fens and some muskeg areas. Some Histosols have been drained, especially to ...
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 wedges at the most easily erodible parts of the parent rock .
Eutric Brunisols have the same basic properties as Melanic Brunisols, except that the Ah horizon, if any, is less than 10 cm thick. Sombric Brunisols have an Ah horizon at least 10 cm thick, and are acid and their pH is below 5.5. Dystric Brunisols are acidic and do not have an Ah horizon 10 cm thick.
Like Gelisols, Histosols have greatly restricted use for civil engineering purposes because heavy structures tend to subside in the wet soil. In USDA soil taxonomy, Histosols are subdivided into: Folists – Histosols that are not saturated with water for long periods of time during the year.
Prior to the development of pedology in the 19th century, agricultural soil science (or edaphology) was the only branch of soil science.The bias of early soil science toward viewing soils only in terms of their agricultural potential continues to define the soil science profession in both academic and popular settings as of 2006.