GRUBEN (Grüebu) (VS)
Active rock glacier
Elevation: 2760-2920 m - Massif: Valais Alps (Fletschhorn) - Commune: Saas-Balen (VS)
Gruben rock glacier consists of a rooting zone formerly originating from a debris-covered glacier and a wide body down to the front. The uppermost half of the rock glacier is moving back towards the glacier (like a back creeping push-moraine) and a significant subsidence of the surface (up to 50 cm in 2013) is taking place during summer independently of the flow rate. The cause of the subsidence is probably to be sought in massive ice occurring beneath a surface blocky layer not thick enough to prevent ice melt during the summer. The subsidence decreases downwards gradually. Our monitoring survey started in 2012. The site is part of the national permafrost monitoring network PERMOS as a “kinematics” site.
Measurements and observations
Thermal (ground surface temperature : GST)
Measured horizontal flow field (mean annual velocity).
Annual 3D surface velocity. Mean of a set of points in the selected parts of the rock glacier.
3D surface velocity derived from a permanent GNSS station located on the main rock glacier tongue.
Daily ground surface temperature (GST) in selected measurement locations on the rock glacier.
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). Mean of n sensors localized on permafrost terrain.
PERMOS 2019. Permafrost in Switzerland 2014/2015 to 2017/2018. Noetzli, J., Pellet, C., and Staub, B. (eds.), Glaciological Report (Permafrost) No. 16-19 of the Cryospheric Commission of the Swiss Academy of Sciences, 104 pp, DOI:10.13093/permos-rep-2019-16-19.
Kääb, A., Haeberli, W. and Gudmundsson, G. H. (1997). Analysing the Creep of Mountain Permafrost using High Precision Aerial Photogrammetry: 25 Years of Monitoring Gruben Rock Glacier, Swiss Alps. (pdf)
Kääb A., Haeberli W. und Teysseire P. (1996). Entwicklung und Sanierung eines Thermokarstsees am Gruben-Blockgletscher (Wallis). UKPIK (Institut de Géographie de l'Université de Fribourg) 10, 145-153.