La répartition du pergélisol dans trois éboulis alpins du massif de la Dent de Morcles (Valais, Alpes suisses)
Sub-surface geolectrical prospecting (vertical soundings, electrical mapping), associated with thermal measurements of the ground surface (Bottom Temperature of the winter Snow cover, continuous thermal measurements) were carried out to determine the distribution and characteristics of permafrost in...
| Published in: | Géomorphologie : relief, processus, environnement |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | French |
| Published: |
Groupe français de géomorphologie
2008
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| Subjects: | |
| Online Access: | https://doi.org/10.4000/geomorphologie.6143 http://journals.openedition.org/geomorphologie/6143 |
| Summary: | Sub-surface geolectrical prospecting (vertical soundings, electrical mapping), associated with thermal measurements of the ground surface (Bottom Temperature of the winter Snow cover, continuous thermal measurements) were carried out to determine the distribution and characteristics of permafrost in three limestone talus slopes situated near the lower limit of discontinuous permafrost in the Dent de Morcles Massif (Western Switzerland). The highest electrical resistivities and the lowest temperatures of the ground surface are systematically located in the lower part of the studied talus. In the upper part, resistivity decreases and temperature increases. This suggests that the lower part of the talus probably contains more permafrost than the upper part. However the three investigated talus are quite different. Ice-rich permafrost seems to be present throughout the slope of Les Charmettes talus. In the col du Fenestral talus, permafrost is uncertain whilst permafrost may possibly be present in the lower part of Creux du Buis talus. The presence of permafrost in the lower part of talus is typical of permafrost distribution in alpine talus. This distribution can be explained by complex air circulation, associated with other factors such as the snow redistribution by avalanches and the high macro-porosity of the talus. Des mesures de la résistivité électrique du terrain (sondages à la verticale et « traînés ») associées à des mesures thermiques de la surface du sol (température basale du manteau nival hivernal ou Bottom Temperature of the winter Snow cover et enregistrements en continu), ont été effectuées afin de déterminer la répartition et les caractéristiques du pergélisol dans trois éboulis, constitués de fragments calcaires, situés à proximité de la limite inférieure du pergélisol discontinu dans le Massif de la Dent de Morcles (Suisse occidentale). Les résultats obtenus indiquent que les résistivités électriques maximales et les températures de surface les plus froides se situent systématiquement dans la ... |
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