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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 characteristic of Gelisols.
Permafrost temperature profile. Permafrost occupies the middle zone, with the active layer above it, while geothermal activity keeps the lowest layer above freezing. The vertical 0 °C or 32 °F line denotes the average annual temperature that is crucial for the upper and lower limit of the permafrost zone, while the red lines represent seasonal temperature changes and seasonal temperature ...
Cut-away section of soil, showing movement of soil layers due to cryoturbation. In gelisols (permafrost soils), cryoturbation (frost churning) refers to the mixing of materials from various horizons of the soil down to the bedrock due to freezing and thawing. Cryoturbation occurs to varying degrees in most gelisols.
About 1,000 soil subgroups are defined in the United States. [6] A soil family category is a group of soils within a subgroup and describes the physical and chemical properties which affect the response of soil to agricultural management and engineering applications. The principal characteristics used to differentiate soil families include ...
Cryoturbation is the dominant force operating in the active layer, and tends to make it generally uniform in composition throughout. However, variation in the composition of soils due to differences in parent rock are very marked in permafrost regions due to the low rate of weathering in the very cold climate.
Alaska holds the all-time U.S. record. The mercury plummeted to 80 degrees below zero on Jan. 23, 1971, in Prospect Creek, north of Fairbanks.
Today's NYT Connections puzzle for Wednesday, January 8, 2025The New York Times
These soils have permafrost (permanently frozen material) within one metre of the surface (2 m if the soil is strongly cryoturbated; i.e., disturbed by frost action). As permafrost is a barrier to roots and water, the active layer (seasonally thawed material) above it may become a saturated, semifluid material in spring.