A talik is a layer of year-round unfrozen ground

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 that lies in permafrost

Permafrost

In geology, permafrost, cryotic soil or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of...

 areas. In regions of continuous permafrost, taliks often occur underneath shallow thermokarst

Thermokarst

Thermokarst is a land surface characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws, that occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Swiss Alps...

 lakes and rivers, where the deep water does not freeze

Freezing

Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....

 in winter, and thus the soil underneath will not freeze either. Sometimes open, closed and through talik are distinguished. These terms refer to whether the talik is completely surrounded by permafrost, is open to the top or open to both top and unfrozen layers beneath the permafrost, respectively.

Supra-permafrost taliks

Due to climate fluctuation or change, some permafrost regions may develop an unfrozen layer between the seasonally thawing/freezing active layer and the permafrost. The layer is called supra-permafrost (above the permafrost) talik; it is different from traditional taliks, which are usually associated with water bodies, in that supra-permafrost talik occurs because the ground that thawed in the summer does not completely refreeze in the winter. Calculations show that climate warming would induce supra-permafrost taliks in intermediately cold regions (in very cold regions, warming simply induces a deeper summer thaw without forming the talik layer; while in warm, shallow permafrost regions, permafrost quickly disappears). This type of taliks has recently been observed in Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. With time and continued increase in air temperature or snow depth, this talik layer will become thicker and thicker and the deep permafrost layer would eventually disappear.