Involution

A structure that develops within the active layer of the Periglacial (permafrost) zone. Cryoturbation (seasonal freezing) causes movement within the layer and sorting of its component materials. Involutions help to define the area of ancient periglacial zones but their action can cause disturbance or mixing of archaeological deposits. Involutions may also be confused with archaeological features.

A structure that develops within the active layer of the periglacial zone. Cryoturbation causes movement within the layer and sorting of its constituents. Involutions formed by this process may consist of tongues or pillars of fine material which extend into overlying sand and gravel, or they may be festoons of coarser material, pulled up into the active layer from underlying sediments. Pockets filled with finer material are a type of involution which develops characteristically on the surface of chalk. Involutions are important because they help to define the area of ancient periglacial zones (although involutions are not absolutely diagnostic of periglacial activity). Archaeologists have frequently confused them with archaeological features, and great care needs sometimes to be exercised when excavating sites.