Periglacial and permafrost conceptual ground models for Great Britain

• Published in: Geological Society, London, Engineering Geology Special Publications
• Main Authors: Murton, Julian B., Ballantyne, Colin
• Other Authors: Griffiths, J. S., Martin, C. J.
• Format: Book Part
• Language: English
• Published: The Geological Society of London 2017
• Subjects: Ice; Ice Sheet; permafrost
• Online Access: https://risweb.st-andrews.ac.uk/portal/en/researchoutput/periglacial-and-permafrost-conceptual-ground-models-for-great-britain(52f72d51-d211-40a3-b972-67ed346d7aba).html; https://doi.org/10.1144/EGSP28.5

Periglacial environments are characterized by cold-climate non-glacial conditions and ground freezing. The coldest periglacial environments in Pleistocene Britain were underlain by permafrost (ground that remains at or below 0°C for two years or more), while many glaciated areas experienced paraglacial modification as the landscape adjusted to non-glacial conditions. The growth and melt of ground ice, supplemented by temperature-induced ground deformation, leads to periglacial disturbance and drives the periglacial debris system. Ice segregation can fracture porous bedrock and sediment, and produce an ice-rich brecciated layer in the upper metres of permafrost. This layer is vulnerable to melting and thaw consolidation, which can release debris into the active layer and, in undrained conditions, result in elevated porewater pressures and sediment deformation. Thus, an important difference arises between ground that is frost-susceptible, and hence prone to ice segregation, and ground that is not. Mass-movement, fluvial and aeolian processes operating under periglacial conditions have also contributed to reworking sediment under cold-climate conditions and the evolution of periglacial landscapes. A fundamental distinction exists between lowland landscapes, which have evolved under periglacial conditions throughout much of the Quaternary, and upland periglacial landscapes, which have largely evolved over the past c. 19 ka following retreat and downwastage of the last British–Irish Ice Sheet. Periglacial landsystems provide a conceptual framework to interpret the imprint of periglacial processes on the British landscape, and to predict the engineering properties of the ground. Landsystems are distinguished according to topography, relief and the presence or absence of a sediment mantle. Four landsystems characterize both lowland and upland periglacial terrains: plateau landsystems, sediment-mantled hillslope landsystems, rock-slope landsystems, and slope-foot landsystems. Two additional landsystems are also ...