Ring ridge hummocky moraines in northern Finland

Abstract

Ring ridge till formations were studied as to form, material composition, structure, age and location in relation both to the surrounding terrain and to other local till accumulations. The high frequency of ring ridges, their occurrence in tight clusters, their situation in sheltered hollows or slopes facing away from the edge of the ice sheet, the variation found in the form of the ridges within the same ridge field, the dual structure of some ring ridges and till fabric indicate that the ridges are dead‑ice formations. Pollen analysis and glacial drainage channels cutting across some ring ridge fields and ring ridges indicate that the ridges were laid down on the melting of the ice sheet.