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| Titel |
Verification of Geophysical Models of the Permafrost Distribution within an Alpine Talus Slope Using Borehole Information, Valais, Swiss Alps |
| VerfasserIn |
C. Scapozza, C. Lambiel, E. Reynard, L. Baron, L. Marescot |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027493
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| Zusammenfassung |
| In order to determine the spatial extension and the characteristics of the permafrost within
alpine talus slopes, thermal and geoelectrical measurements were carried out in several sites
of the Swiss Alps (Lambiel 2006, Pieracci et al. 2008). The observations and the
measurements carried out at the study sites allowed proposing a model of the permafrost
distribution in talus slopes located within the Alpine periglacial belt (Lambiel & Pieracci
2008). According to this model, permafrost appears likely in the lower part of the slope,
whereas it is generally improbable upslope. In order to validate the model, in the
Attelas talus slope (Verbier area, Valais Alps, 2600-2800 m a.s.l., west-facing flank of
the Mont Gelé) a fix Electrical Resistivity Tomography (ERT) profile along an
upslope-downslope transect composed by 48 electrodes (4 meters interval) was installed in
summer 2007, and three boreholes were drilled along the ERT profile in autumn
2008.
The Attelas talus slope is a cone-shaped landform, composed by paragneiss and affected
by solifluction processes in the upper-mid part of the slope. A protalus rampart at the foot
of the talus suggests the presence of creeping permafrost in the lower part of the
slope.
The ERT of July 2008 shows a difference in resistivities between the lower and the upper
part of the slope. A resistive body with values higher than 25 kΩm and a thickness of about
15 meters is present in the lower part of the slope, as imaged by both apparent and inverted
resistivities. In the central part of the slope, a layer of 15-20 meters with lower
resistivities ( |
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