The research group CNRS UMR 6042 (GEOLAB Laboratory, Clermont-Ferrand) continues its periglacial investigations within various research projects. The last field season of a four-year programme led by Denis Mercier and supported by the French Polar Institute took place in Northwest Spitsbergen. It is aimed at paraglacial dynamics including relationships between geomorphic processes and vegetation colonization.
In Iceland, the scientific cooperation between Armelle Decaulne and Thorsteinn Saemundsson (Natural Research Centre of Northwestern Iceland, Saudårkrokur) consisted of a joint investigation of snow-avalanche and debrisflow processes (geomorphic impact, triggering factors, slope deposit stratigraphy, relative dating using lichenometry and vegetation cover) and in a study of associated natural hazards in fjords and valleys in north and northwest Iceland. They co-organized with Achim Beylich (Geological Survey of Norway) the First SEDIFLUX Science meeting. The Second SEDIFLUX Science Meeting is organized by Samuel Etienne ([email protected]) in Clermont-Ferrand in January 2005 (see Other News).
Results from previous field seasons in Alexander Island (Antarctic Peninsula) and in the Falkland Islands are being processes by Marie-Françoise André, Kevin Hall and Joselito Arocena with a particular focus on past and present alveolar weathering, thermally-driven processes, and stone runs.
At the CNRS UMR M2C 6143 (Caen University), various research programmes are dedicated to morphodynamics in periglacial environments. In order to constrain the evolution of fault scarps and steep slopes in areas that have experienced periglacial erosion during the Quaternary, a physical modelling experiment was carried out in a cold room. Boundary conditions were assessed with reference to field data obtained along the La Hague Fault Scarp (North Cotentin, Normandy). Data from 41 freezethaw cycles point out that scarp degradation mainly results from three interactive processes: (i) cryoexpulsion that modifies the soil rheology, ii) combined effects of frost creep and gelifluction which lead to slow and gradual downslope displacements of the active layer, and iii) debris flows that induce rapid mass movements when the active layer is water saturated. One of the most surprising results of this physical modelling is the importance of rapid waterinduced mass displacement during thawing. This appears to be a very efficient process in scarp erosion and degradation.
A new programme funded by the INSU/CNRS (Programme National “Relief de la Terre” 2004) is dealing with the role of debris flows on slope degradation in periglacial environments. A research programme of the University of Sussex (Julian Murton) funded by the U.K. Natural Environmental Research Council on “Bedrock fracture by ice segregation” has been active in Caen since 2003. A new programme of the Cardiff group (C. Harris) started in 2004 on the topic of physical modelling of mass-movement processes on permafrost slopes: both fullscale (Caen refrigerated tanks) and small-scale physical modelling (Cardiff Geotechnical Centrifuge) are developed to investigate mass movement processes in clay-rich soils at steep gradients.
Martian permafrost structures were investigated at the Laboratory IDES (UMR 8148, Orsay). The frozen ground of Mars is likely to contain water ice that may be studied by either geomorphic or geophysical approaches. The Gamma-Ray Spectrometer on board the Mars Odyssey spacecraft gave new data about the distribution of hydrogen, and thus ground ice, in the first metre of the planet. We interpret these data in connection with the geomorphic features observed at the same latitudes where ground ice is present (N. Mangold). This work provides a tool for studying recent features associated with the presence of very superficial ice. Investigation of the geophysical properties of Martian frozen ground by radar experiment is currently the topic of preliminary research prior to the first result of the radar MARSIS onboard Mars Express. Radar data will allow the identification of ground ice and possibly of ground water at depth of the order of several hundreds of metres. Current research concerning radar are in progress at the Laboratory IDES. It is focusing on the propagation wave of the radar response in a one cubic metre permafrost mass in a cold room. The propagation of a 08C interface have been detected with a GPR and validated with thermocouples (P. Tucholka, A. Saintenoy, F. Costard).
François Costard ([email protected])