C. Harris and M. Kern-Luetschg (Cardiff University), J. Murton (University of Sussex), M. Davies (University of Auckland) and F. Smith (University of Dundee) have continued their programme of experimental modelling of solifluction processes at UMR CNRS 6143 M2C Caen, France, in collaboration with M. Ertlen-Font.
This project, funded by the UK’s NERC and the France’s CNRS, has successfully simulated solifluction processes in two identical slope models, one subjected to one-sided freezing and thawing with a basal water supply, and the second in which a refrigerated base plate maintained a basal permafrost zone and active-layer freezing was two sided. Over the three-year project, models have been subjected to 17 freeze-thaw cycles in total, with hourly monitoring of soil temperatures, pore water pressures, frost heave, thaw settlement and down-slope soil movements. Excavation of buried displacement columns has revealed clear contrasts in the style of solifluction resulting from one-sided seasonal freezing and thawing in the absence of permafrost, and two-sided active-layer freezing associated with permafrost.
In parallel to this full-scale modelling, the Cardiff group have undertaken scaled centrifuge modelling of solifluction under one-sided (seasonally frozen ground) and two-sided (permafrost) freezing regimes, using the same slope geometry and test soil as in the full-scale model. Research is funded by the UK EPSRC, and the centrifuge technique has proved highly effective, with results entirely consistent with the full-scale modelling outcomes. The project has also included detailed field measurements in Dovrefjell, Norway (seasonally frozen) and Endalen, Svalbard (permafrost) so that centrifuge and full-scale modelling will be validated against field data. Finally, new numerical approaches based on advanced Thermal-Hydraulic-Mechanical modelling are under development at Cardiff University by H. Thomas, P. Cleall and Y. Li. Numerical models will be calibrated using data from the physical modelling programme.
At Sussex University, setting up the cold room for permafrost experiments continues, as monitoring equipment and hardware were installed. Blocks of chalk from a variety of lithostratigraphic units have been obtained from southern England, and are ready to be instrumented for tests on ice segregation and rock fracture beneath horizontal and steeply inclined surfaces.
The influence on Pleistocene permafrost and periglacial processes on the English landscape continues to be examined. S. Gurney (University of Reading) is investigating a site in Herefordshire, which preliminary work has revealed may contain several relict cryogenic mounds. Electrical resistivity techniques are being employed to map sediment structures in the sub-surface, which may provide further evidence for the origin of the features. At Pegwell Bay, in Kent, J. Murton, C. Whiteman (Brighton University), M. Bateman (Sheffield University) and C. Baker (St Lawrence College) are studying stratigraphic sequences extending back from Marine Isotope Stage 2 to 4 and probably earlier. A field trip celebrating the 50th anniversary of the seminal paper on the periglaciation of southern England by T. Punga was led by P. Worsley (Oxford University), visiting sites between Kent and Devon. The role of permafrost on landscape evolution in southern England is currently being re-evaluated by J. Murton, integrating studies of Tertiary erosion surfaces, Cenozoic drainage evolution, crustal uplift, and experimental work on bedrock fracture and solifluction.
Julian Murton (email@example.com)