Disturbances are elements in the landscape (either natural or anthropogenic) which interact with the permafrost layer leading to local anomalies in thermal, hydrological, hydrogeological, or hydrochemical conditions. Hence, such disturbances can lead to the formation of taliks. A talik is defined as a layer or body of unfrozen ground existing continuously for more than a year in permafrost regions. The temperature of a talik ranges from above 0°C (noncryotic taliks) to below 0°C (cryotic taliks).
Different types of disturbances cause different types of taliks.
Water has the ability to store and vertically transfer heat energy. The type and extent of the taliks (also referred to as "lake taliks") is related to the depth and water volume of the overlying water body. Larger water bodies can store and transfer more energy downward (see figure). Under lakes, both closed and open taliks can be formed.
Below large lakes, usually open taliks form, connection suprapermafrost and subpermafrost water.
Below small lakes, closed taliks which over time change into transient taliks may form. These are taliks which are gradually being eliminated by freezing. Expansion of thaw lake surface area in continuous permafrost zones will result in more talik development.
Just as lakes, rivers can lead to the formation of both closed and open taliks, depending on the the characteristics of the river. Large rivers often promote the formation of open taliks.
Elements/changes in landscape caused by human activity, i.e.
Artificial taliks can be easily formed in a discontinuous permafrost zone because a small, often rather short-term, change in hear exchange condition on the ground surface is sufficient for taliks to be formed.
Other factors which promote talik formation, i. e.:
References:
http://www.physicalgeography.net/fundamentals/10ag.html
http://www.springerreference.com/docs/html/chapterdbid/330973.html
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