Pleistocene cryopediments on variable terrain

Similarities and differences in the processes and conditions of cryopediment formation are illustrated in two particular type regions. Cryopediment gradients range from 1–3° in the Czech Republic and from 0.03–0.05° in the lowlands of Belgium and the Netherlands, widths are from hundreds of metres to kilometres and underlying substrates vary from bedrock to unconsolidated sediment. The knickpoint between backslope and cryopediment surface is generally poorly developed on soft substrates but is sharp in bedrock substrates. Surface runoff, operating in sheets or concentrated, is inferred to have been the main process of sediment removal and transport on the cryopediment surface. The diversity in cryopediment morphology reflects the balance between the energy required and that available for transporting the sediment supplied. A resistant substrate produces relatively steep cryopediment gradients, and parallel backslope retreat may occur. In unconsolidated substrates, (very) low relief develops as a result of wash processes. Since large amounts of surface runoff cannot be generated on the highly permeable substrates, cryopediment surfaces must have developed under periglacial conditions with (thick) winter snow cover releasing meltwater in a short time over a frozen (and thus impermeable) soil. Due to repetitive periglacial conditions and progressive base‐level lowering, some cryopediments may have developed polycyclically. Copyright © 2008 John Wiley & Sons, Ltd.