Cryoturbation

Cryoturbation ( Greek: kryos , frost, and lat. Turbare , swirling around) is the mixing of the subsurface near the surface by freezing and thawing. The cryoturbation is a phenomenon of the periglacial areas , that is, the process is essentially linked to the presence of permafrost , it is a periglacial morphology.

Cryoturbation requires a certain amount of water saturation as well as thawing and freezing cycles. The summer thawing layer above the permafrost is known in technical terms as the active layer and represents the effective area of ​​the cryoturbation. The thawing depth is usually 50 to 70 cm.

Frost pattern floor on Cassons near Flims (Switzerland)

Ice wedge polygons in Svalbard

Process flow

Due to the permafrost in the subsoil, the seepage of water from the summer thaw is significantly restricted or impossible. This results in a high water saturation in the active layer . The re-freezing of this thawing layer towards winter takes place from top to bottom. This creates a load pressure in the area between the permafrost in the subsoil and the re-frozen layer of the topsoil. The water saturation of the substrate enables the muddy fine soil material to be pressed out through crevices and cracks on the surface. The muddy material usually flows out like patties on the surface. The multiple repetition of this process over many thawing and freezing cycles leads to a thorough mixing of the entire thawing layer ( active layer ).

Cryoturbation also causes processes such as subsidence in thawing floors and frost uplift . This creates, for example, frost pattern floors and pocket floors or surface shapes such as pals .

consequences

Cryoturbation leads u. U. to damage to artifacts. Edge damage caused by this is referred to as cryo-retouching.

See also

• Soil-forming processes
• Frost bake
• Frost weathering

literature

• L. Eißmann: Periglacial processes and permafrost structures from six glacial periods of the Quaternary. A contribution to the periglacial geology from the point of view of the Saale - Elbe area. (= Altenburg natural science research. Volume 1). Mauritianum, Altenburg 1981, DNB 820062073 .
• Arno Semmel: Periglacial morphology. (= Income from research. Volume 231). Knowledge Buchges., Darmstadt 1994, ISBN 3-534-01221-6 .
• Bernhard Krummenacher among others: Periglacial processes and forms in the Furggentälti, Gemmipass. (= Federal Institute for Snow and Avalanche Research Communications. No. 56). Federal Institute for Snow and Avalanche Research , Davos 1998.