Talik

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Types of taliks

As Talik (plurality Taliki or Taliks ) is in permafrost regions , a region unfrozen soil designated by a local abnormality of the thermal, hydrological , hydrogeological or hydro chemical originated conditions. Most definitions of the term also assume that the unfrozen state must last for at least one year in order to be considered a Talik, as otherwise it would have to be classified as thawed soil. There is also a lack of uniformity with regard to the question of whether the unfrozen soil below the permafrost level, the so-called low frost soil, can be described as Talik.

Taliki are classified in a number of ways, particularly according to their location within the permafrost. For example, a distinction is made between open and closed taliki, the latter have no contact with the thawed soil and are surrounded by frozen soil. Another classification is based on the physical cause of the unfrozen state. One form are hydrothermal taliki, which are caused by the warming effect of the surface water above.

Taliki are a common phenomenon in the temperature profile of the permafrost, even in the continuous zone. They can be caused by changes in the temperature balance and indicate permafrost degradation. On the other hand, they can also occur in an area that is in equilibrium with the climate and are caused by local heat sources, whereby movements of the groundwater in particular can be responsible here - since the frozen soil is impermeable to water, these are limited to Taliki in permafrost areas.

Classification

A basic criterion is a distinction based on temperature. In most cases this is above the freezing point of water. But there are also so-called cryotic taliki , the temperature of which is below 0 ° C, for example when they are traversed by mineralized groundwater.

Depending on the location relative to the surrounding permafrost, the following types are mainly distinguished:

  • Closed Talik : A Talik of this type has no contact with the thawed soil; it is completely surrounded by permafrost or reaches the surface of the soil at a point where it does not freeze. The latter can typically occur under lakes or rivers. The temperature is above 0 ° C due to the heat storage of the surface water, which is why it is non-cryotic taliki.
  • Open Talik : When a talik completely penetrates the permafrost, it is said to be "open". Such a talik establishes a connection between the surface water and the water below the permafrost. In continuous permafrost, open taliki are rare, they can form under large lakes or rivers. Open taliki can be cryotic or non-cryotic.
  • Lateral talik : This is a talik that is surrounded both above and below by year-round frozen ground. Such taliki can be cryotic or non-cryotic.
  • Isolated Talik : Taliki of this type are entirely surrounded by frozen ground. They are often cryotic, but they can also be non-cryotic.
  • Transient Talik : When a talik gradually disappears due to the freezing of the ground, it is called "transient". Typically they develop under drying up lakes. As the permafrost spreads, a closed into an isolated and transient valley develops.

Another classification differentiates according to the physical cause of the unfrozen state. There are five main types:

  • Thermal Talik : This is a non-cryotic Talik that is formed by the local heat profile of the soil. Thermal taliki are mainly found in areas with discontinuous permafrost, typically on the edge of the permafrost area. In these areas the solar radiation is stronger, which means higher air and ground temperatures are caused. In addition, the insulating effect of seasonal snow cover can play a role and result in a higher average temperature of the soil.
  • Hydrothermal Talik : Such a Talik is created by the warming effect of surface water, it is therefore non-cryotic. These can be taliki under lakes or rivers, but there are also taliki of this type under the seabed. Furthermore, such taliki can arise under plains that are flooded irregularly but often. Such taliki can also be found under glaciers if meltwater flows at their bottom.
  • Hydrochemical Talik : This is a cryotic Talik that is prevented from freezing by mineralized groundwater that permeates the Talik.
  • Geothermal Talik : A talik of this type is caused by geothermal anomalies caused by processes inside the earth. The geothermal heat flow in the earth's interior is transferred along active faults or in the vicinity of volcanoes to pressurized water below the permafrost. Thus, such taliki are non-cryotic.
  • Artificial Talik : These are caused by human activities in the permafrost area. Examples are taliki under artificial water reservoirs, spoil heaps, buildings or streets. In the discontinuous permafrost area, the smallest changes in the heat balance are sufficient to create an artificial talik. They can be cryotic or non-cryotic.

meaning

Taliki and their development have a clear influence on vegetation, surface and groundwater hydrology, the landscape and also on the human infrastructure in the permafrost area. They also provide an extremely suitable environment for soil microorganisms , which can convert organic material located there - such as dead plants and animal carcasses preserved in permafrost - into methane . Methane releases in meltwater lakes of the permafrost are reported to be a significant source of methane in the atmosphere.

literature

  • Hugh M. French: The Periglacial Environment. 3rd edition, Wiley-Verlag, Chichester 2007, ISBN 0-470-86588-1 .
  • Tingjun Zhang: Talik. In: Vijay P. Singh, Pratap Singh, Umesh K. Haritashya (Eds.): Encyclopedia of Snow, Ice and Glaciers. Springer, Dordrecht 2011, pp. 1143f, ISBN 978-90-481-2641-5 .

Web links

Individual evidence

  1. ↑ a b c d e Tingjun Zhang: Talik. See literature.
  2. ^ A b Albert L. Washburn: Geocryology. Edward Arnold Publishers, London 1979, pp. 55f, ISBN 0-7131-6119-1 .
  3. ^ A b c French: The Periglacial Environment. P. 105f, see literature.
  4. ^ Dennis M. Filler, Ian Snape, David L. Barnes: Bioremediation of Petroleum Hydrocarbons in Cold Regions. Cambridge University Press, Cambridge 2008, pp. 50f, ISBN 0-521-86970-6 ( Google Books ).