4th Swiss Geoscience Meeting, Bern 2006 Permafrost distribution in talus slopes

• Main Author: Lambiel Christophe
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.537.9375; http://geoscience-meeting.scnatweb.ch/sgm2006/SGM06_abstracts/19_Changing_Alp_Cryo/Lambiel_Christophe_Talk.pdf

In the context of a warmer climate, the localization of permafrost in steep sedimentary terrain is of great importance. In order to identify the permafrost distribution and characteristics in the talus slopes of the alpine periglacial belt, about 15 talus slopes located mainly in the Mont Gelé (Verbier-Nendaz) and Arolla areas (Swiss Alps) were studied. The traditional methods of permafrost prospecting were used, i.e. ground surface temperature measurements at the base of the snow cover (BTS), year-round ground temperature measurements and DC-resistivity prospecting. In most cases, permafrost was found in the lower part of the slopes. At this place, electrical resistivities are the highest (Figure 1). The typical DC resistivity curves display a resistive layer near the surface. Then, the resistivities decrease. A third thicker layer with higher resistivities can then be identified, before the values decrease again (Figure 2). The presence of a conductive layer (blocks supported by a fine-grained matrix) above the third layer is an argument to interpret this one as frozen sediments. Another argument is the shape of the curves, which is typical for permafrost in coarsy sediment terrain. It corresponds to what is generally measured on rock glaciers. The difference is the resistivity value of the third layer, which is generally higher in rock glaciers than in talus slopes. Finally, BTS values are the coldest in the lower part of the slopes.