Thermokarst

As thermokarst a country forming process in periglacial is denoted by thawing permafrost. The original derivation of the term thermokarst comes from the certain similarity of the resulting landforms with the classic carbonate karst. The shaping processes, however, differ significantly. Processes associated with the thawing of ice -bound in the ground, called thermokarst. The general suffered as a result of fluid and temperature changes geomorphological processes are treated under the term pseudo- karst.

Development process

The thawing of the permafrost ground ice contained in the soil melts. The volume loss gives rise to characteristic landforms by the depression of the land surface. The term thermokarst includes only the pure reduction due to volume loss, but not the erosion by flowing water. If also mechanical erosion occurs by flowing water, it is called thermal erosion. In a broader sense are referred to with thermokarst and the resulting relief structures. In general, the formation of thermokarst to a high ice content ( ice wedges, Segregationseis ) is bound in the soil. The higher the volume of ice, the more the thermokarst can mint with the melting of the ice. The irregular subsidence of the land surface caused sinks that fill up quickly with water and allow so-called thermokarst lakes arise. These water bodies support through its higher heat capacity than the air and the ground, the more thawing of the permafrost under the lake and a progressive sinking. Due to expansion in the horizontal is thermokarst lakes can unite to form larger bodies of water.

Distribution areas

Thermokarst is widely used in the permafrost regions of the world: Siberia, Alaska and Canada. To a lesser extent thermokarst occurs in sedimentary deposits of the high mountain regions. Thermokarst is a typical post-glacial formation, particularly hard by global warming began with the beginning of the current warm period, the Holocene.

Different Types

There are several thermokarst forms: thermokarst lakes, thermokarst depressions and thermokarst Hill. Special shapes are the oriented thermokarst lakes, which are found in the lowlands of the Arctic coastal areas. These lakes have a clearly pronounced stretching along a longitudinal axis, thus are usually elliptical, the orientation of the longitudinal axis in all lakes differs only slightly from one another. A common hypothesis for this phenomenon tries to explain perpendicular to the longitudinal axis of the lakes the emergence of Seeachsen orientation with strong prevailing wind directions.

Effects on the environment

Thermokarst may be due to the global warming and the warming of the permafrost also a highly controversial topic. By thermokarst are released back to a great extent in permafrost since year tens of thousands of frozen plant residues for decomposition, so that the greenhouse gases methane and carbon dioxide are released. The formation of thermokarst can also become a threat by existing or yet -to-build infrastructure in the Arctic regions are (pipelines, buildings, runways, etc.).