Thermokarst


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Thermokarst

 

the formation of subsidence and collapse landforms and subsurface cavities because of the melting of underground ice or the thawing of frozen ground that, in turn, are the result of an increase in the annual average air temperature or in the range of variation of soil temperature.

Thermokarst is a phenomenon specific to the area of occurrence of permanently frozen rock. It results in the formation of typical landforms, such as lake basins, alasy, sinkholes, minor depressions (bliudtsa), and other negative topographic forms, and in collapse formations and cavities in the subsoil layer (grottoes, recesses, and pits). Thermokarst usually accompanies other processes, such as thermal contraction and gravity displacement of thawed rock; it may be combined with surface and subsoil wash, solifluction, suffosion, erosion, and abrasion. It also develops in regions of stable and even aggrading cryolithozone as a result of disturbances of the dynamic equilibrium in the water and the thermal regimes of the earth’s surface. It may also be caused by industrial and civil engineering construction, deforestation, and numerous other factors of human economic activity.

Among the measures for the prevention and control of thermokarst are (1) the protection of permanently frozen rock and subsurface ice from melting and thawing during the construction and operation of structures, (2) the thawing of frozen, ice-containing beddings before construction, and (3) drainage of areas.

REFERENCE

Kachurin, S. P. Termokarst na territorii SSSR. Moscow, 1961.

IU. T. UVARKIN and A. A. SHARBATIAN

References in periodicals archive ?
15 in the journal Nature Communications, focuses on the carbon released by thawing permafrost beneath thermokarst lakes.
The 2007 Anaktuvuk River Fire is the largest (104000 ha) and longest-burning (almost 3 months) fire known to have occurred on the North Slope of Alaska and initiated widespread thermokarst development (Jones et al.
The region is characterized by a wide development of thermokarst forms of relief [28].
Hinzman, "Shrinking thermokarst ponds and groundwater dynamics in discontinuous permafrost near Council, Alaska," Permafrost and Periglacial Processes, vol.
"Thermokarst Lake Morphometry and Erosion Features in Two Peat Plateau Areas of Northeast European Russia." Permafrost and Periglacial Processes 24 (1): 75-81.
Cory and her team studied 27 melting permafrost sites in Alaska and identified seven thermokarst failures, large patches of the Arctic tundra that have melted.
Subsequently, the clay-filled fissures above this were opened up in order to gain access via a series of short crawling passages to the top of the dolomite and a number of vertical solution features (palaeokarst or thermokarst), some of which were filled with extractable mineral.
Shuchman (Michigan Tech Research Institute, Ann Arbor) and Josberger (USGS, Washington Water Science Center, Tacoma) report the results of diverse field and lab studies conducted by seasoned and new researchers on the glacier's surging dynamics; its hydrology; human history; and flora and fauna, including trees' unique thermokarst features indicative of the changing climate.
'If the active layer of permafrost, which melts seasonally, reaches a certain depth, then thermokarst processes will accelerate [leading to an increase in lakes], and the permanent ancient ice, which is typically at a depth of around 40 metres in Yamal, will degrade and cause the landscape to erode very quickly,' says Romanenko.
"But there are increasing signs of warming permafrost in the Swiss Alps [e.g., rock fall activity in permafrost regions, increase of creep rates in icy sediments, formation of thermokarst, and instability of infrastructure]."
Polygon-junction ponds are also common in this region of the Canadian Arctic and are the product of thermokarst processes, which are induced by changes in the thermal equilibrium of ice-rich sediments.
This feature may attest to a lengthy stagnant ice field on insular heights of glacial origin (Karukapp & Raukas 1994; Lundqvist & Wohlfarth 2001), resultant slope- and thermokarst processes, and burial of organic sediments under colluvium.