Active rock glacier
Elevation: 2350-2840m - Massif: Valais Alps (Mischabel) - Commune: St Niklaus (VS)
The Dirru rock glacier, located on the orographic right side of the Mattertal, is one of five rock glaciers that were classified as being “destabilized” (unusually high motion rate) in the mid-2000s using satellite interferometry data (InSAR). It is a landform slightly longer than 1km. composed of a superposition of several lobes. The current active tongue is destabilized at least since the early 1970s (3.7 - 4.5 m/y). A strong erosion of its front occurred in 1995, delivering important quantities of debris into the Geisstriftbachs gully. Since that time, the edge of the rock glacier front has always been located at about the same position, whereas the rock glacier itself has continuously moved at a velocity of 5 to 8 m/y. The first displacement measurements (DGNSS) were carried out in 2007.
Measurements and observations
Thermal (ground surface temperature : GST)
Geophysics (geoelectric, refraction seismic, georadar)
Remote Sensing (Webcam, LIDAR, aerial image)
Current image of the rock glacier
Timelapse based on selected webcam images
Measured horizontal flow field (annual velocity)
Annual velocity. Mean of a set of points selected respectively in the lower and most active part of the rock glacier (blue), the median section (green) and the uppermost area (orange).
Mean annual ground surface temperature (MAGST) in selected measurement locations on the rock glacier.
Contribution of the Ground Freezing and Ground Thawing Indexes to the mean annual ground surface temperature (MAGST) on a set of selected locations (n) on the rock glacier. Or : how cold was the winter and how warm was the summer at the surface of the rock glacier ?
Mean annual dates of the start and end of the snowmelt period (zero curtain phase) on a set of selected locations (n) on the rock glacier.
Kanton Wallis – Dienststelle für Wald, Flussbau und Landschaft (DWFL)
ID eletronic SA
Further measurements are undertaken by the Federal Office for the Environment, ETH Zurich and University of Zurich.
Kummert, M., Braillard, L., Delaloye, R., Bodin, X. (2021). Pluri-decadal evolution of rock glaciers surface velocity and its impact on sediment export rates towards high alpine torrents. Earth Surface Processes and Landforms, 46(15), 3213-3227. DOI: 10.1002/esp.5231
Kummert, M. & Delaloye, R. (2018). Mapping and quantifying sediment transfer between the front of rapidly moving rock glaciers and torrential gullies. Geomorphology 309, 60-76. DOI: 10.1016/j.geomorph.2018.02.021
Kummert, M., Delaloye, R. and Braillard, L. (2017). Erosion and sediment transfer processes at the front of rapidly moving rock glaciers: systematic observations with automatic cameras in the western Swiss Alps. Permafrost and Periglacial Processes 29, 21-33. DOI: 10.1002/ppp.1960
Delaloye, R., Morard, S., Barboux, C., Abbet, D., Gruber, V., Riedo, M. and Gachet, S. (2013). Rapidly moving rock glaciers in Mattertal. In: Graf, C. (ed.) Mattertal – ein Tal in Bewegung. Publikation zur Jahrestagung der Schweizerischen Geomorphologischen Gesellschaft 29. Juni – 1. Juli 2011, St. Niklaus. Birmensdorf, Eidg. Forschungsanstalt WSL. 21-30. (pdf)