Experimental simulation of ice-wedge casting: processes, products and palaeoenvironmental significance
Charles Harris, Julian B. Murton, 2005. "Experimental simulation of ice-wedge casting: processes, products and palaeoenvironmental significance", Cryospheric Systems: Glaciers and Permafrost, C. Harris, J. B. Murton
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In six experiments, model ice wedges 150 mm high and ≤50mm wide were thawed from the surface downward at 30g in a geotechnical centrifuge, simulating ice-wedge casting during progressive active-layer deepening through permafrost. The frozen host soils ranged from sand to silt to clayey silt. Resulting ice-wedge pseudomorphs indicated that the degree of deformation during casting was determined by factors that control thaw consolidation. Hence, deformation increased as the host sediments became finer-grained and more ice-rich. Thaw of host sand at 15 and 20% gravimetric ice content and host silt at 20 and 40% ice content resulted in the formation of partially-developed ice-wedge pseudomorphs with an upper ‘plug’ of sediment derived largely from the cover soil, a central tunnel and a basal plug of sediment. Thaw of host clayey silt at 30 and 60% ice content resulted in the formation of fully developed pseudomorphs that were significantly narrower and shorter than the initial ice wedges. The experiments support the hypothesis that ice-wedge pseudomorphs tend to be better preserved in coarser-grained sediments that are not ice-rich and therefore deform little during thaw of constituent ice wedges. This selective preservation has probably led to underestimation of ice-wedge pseudomorphs in fine-grained soils that were originally ice-rich and therefore a bias towards reconstructing cold temperatures.
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The introduction of the term periglacial by Łoziński in 1909 to describe the cold-climate conditions in the zone adjacent to, but beyond, the Pleistocene glaciers encouraged the separate development of geocryological and glaciological research. Geological and geomorphological processes at the interface between glaciers and permafrost have, as a result, been given less attention than they warrant, and the influence of one on the other has in many respects been neglected. This book includes a collection of papers that emphasize glacier-permafrost interactions. Papers consider permafrost and its influence on glacitectonic processes, glacial meltwater systems and ground-ice development in proglacial and ice-marginal environments. In addition, recent research findings are reported on paraglacial processes, permafrost evolution, rock glaciers, the formation of ice-wedge casts and periglacial slope evolution. It is hoped that this book will stimulate interest in the interface between glacial and periglacial systems, and encourage further collaborative research involving glaciologists and glacial geologists on the one hand, and geocryologists and permafrost scientists on the other.