Convective deformations in slightly lithified sedimentary rocks

Cryogenic Deformation Structures in Late Cenozoic Unconsolidated Sediments of the Tunka Depression in the Baikal Rift Zone

“…The formation of multiple folds (convective instability deformation) in unconsolidated deposits was revealed in the 1960s (Artyushkov, ; Kostyaev, ) and attributed to density inversion. Denser soil above less dense soil is unstable under the force of gravity, and this may cause movement as the upper soil subsides and displaces the lower one.…”

Some late Pleistocene involutions at Dalton‐in‐Furness, northern England

“…In such coarse materials the effective stresses at times of frost heave would greatly exceed the neutral stresses produced in thaw periods but the latter would play an important part in reducing the cohesion of the soil and sustaining a flow of ground water into those areas where the frost penetration was at its greatest. Given time then, frost mounds must have formed on the ground surface and frost cracking of the C 32 R. H. JOHNSON surface took place wherever tensional stresses or dessiccation effects were at their greatest.At the back of the terrace,where for reasons given the stresses at the mollisol/ frozen layer interfaces were at their strongest, involutions would form; and if these were associated with ice veins and frost cracks, then these would provide lines of weakness into which basal sediments could be intruded to form the involution septa (Artyushkov 1965). Such a hypothesis is given strong support from studies of other periglacial phenomena found in similar footslope/rear of terrace locations and also from laboratory simulation experiments.…”