Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging

Abstract

Abstract. Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.

Occurrence, evolution and ice content of ice‐debris complexes in the Ak‐Shiirak, Central Tien Shan revealed by geophysical and remotely‐sensed investigations

“…Lower frequency GPR will allow measurement to greater depths but with the drawback of less detailed information. Geoelectric investigations are especially suitable for higher resolution results including detecting ground ice (Ribolini et al, ; Emmert and Kneisel, ) although the depth of application is quite limited and they require intensive and laborious fieldwork, and are therefore more suitable for smaller landforms.…”

Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

“…1b) to image the internal structure (Hauck and Kneisel, 2008;Kneisel et al, 2008) and to quantify its material composition based on a petrophysical model, the so-called Four-Phase Model (4PM, see below) (Hauck et al, 2011). Previous studies on the internal structure of rock glaciers have revealed large spatial heterogeneities in material composition within single landforms (Emmert and Kneisel, 2017;Hausmann et al, 2012;Monnier and Kinnard, 2013;Springman et al, 2012). 210…”

Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents

“…New approaches include the possible estimation of ground ice variation through subsidence measurements using reflected GNSS signals (Liu and Larson, 2018) or through spaceborne gravity measurements (e.g., Vey et al, 2012). Since information from one method is often ambiguous, many cryogeophysical studies use a combination of different geophysical methods (e.g., Hausmann et al, 2007;Kneisel et al, 2008;Doetsch et al, 2012;Buchli et al, 2013;Parsekian et al, 2015;Briggs et al, 2016;Merz et al, 2016;Pellet et al, 2016;Emmert and Kneisel, 2017;Léger et al, 2017;Mewes et al, 2017).…”