cryoturbation

Cryoturbation is the mixing and disturbance of soil and sediments caused by freezing and thawing in cold climates. It is a key soil-forming process in periglacial environments and is common in tundra, boreal forests, and high alpine areas. Through repeated freeze-thaw cycles, water in the soil forms ice lenses and expands, generating frost heave and mechanical disruption that overturns and blends horizons. As a result, original soil layers can be incompletely sorted, organic matter can be incorporated into mineral layers, and materials from different depths become intermingled. The process can move coarse material toward the surface and bury underlying layers, creating cryoturbated horizons that show mixed textures and colors.

Indicators of cryoturbation include intermingled horizons with irregular contacts, fragmentation of vertical soil structure, mixing of organic and mineral matter, and the presence of buried organic-rich layers at unexpected depths. Cryoturbation is most active in regions with sustained frost and relatively shallow permafrost, such as Arctic and subarctic regions and high mountains, though it also occurs in areas with seasonal ground freezing. It is distinct from other periglacial processes such as solifluction, though it often coexists with them. In soil classification and interpretation, cryoturbation is recognized as a diagnostic feature of cold-climate soils and is used to infer past and present periglacial conditions.

Studying cryoturbation informs understanding of climate history, rates of soil development, and landscape evolution, and it can influence soil structure, moisture regimes, and plant communities by altering horizon arrangement.