The Kandersteg rock avalanche (Switzerland): integrated analysis of a late Holocene catastrophic event

• Published in: Landslides Vol. 17; no. 6; pp. 1297 - 1317
• Main Authors: Singeisen, Corinne, Ivy-Ochs, Susan, Wolter, Andrea, Steinemann, Olivia, Akçar, Naki, Yesilyurt, Serdar, Vockenhuber, Christof
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2020; Springer Nature B.V
• Subjects: Age; Agriculture; Avalanches; Boulders; Catastrophic events; Chronology; Civil Engineering; Cretaceous; Earth and Environmental Science; Earth Sciences; Entrainment; Fluvial sedimentation; Fluvial sediments; Geography; Holocene; Image analysis; Image processing; Image reconstruction; Landslides; Limestone; Mapping; Mechanics; Natural Hazards; Original Paper; Rocks; Sandstone; Sediment; Sediments; Substrates; Tertiary; Valleys; Switzerland; Cosmogenic; Landslide; Kandertal; European Alps; Runout modelling; Cl exposure dating
• ISSN: 1612-510X; 1612-5118
• DOI: 10.1007/s10346-020-01365-y

In this study, we focus on the Kandersteg rock avalanche in the central Bernese Alps in Switzerland. We achieved an improved understanding of the release and emplacement of the rock avalanche through a combination of detailed field mapping, remote image analysis, reconstruction of deposit and source area volumes, and runout modelling with DAN3D. Based on cosmogenic 36 Cl dating of siliceous limestone boulders all across the landslide deposit, we determined an age of 3210 ± 220 years for the event. This age is markedly younger than the previously suggested age of 9600 years. An estimated 750–900 Mm 3 of Cretaceous limestones, siliceous limestones (Oehrlikalk, Kieselkalk and Bänderkalk formations) and Tertiary sandstones of the Doldenhorn nappe detached along pre-existing discontinuities from the northwest face of the Fisistock peak. The sliding body fragmented upon encountering the valley floor and the steep opposite valley wall. Next, the dry fragmented rock avalanche propagated northward over a substrate of fluvial sediments. As it moved, the debris became more fluid through entrainment of water and water-rich sediments, until it finally came to a halt 10 km downstream. The final volume of the deposit is estimated at 1.1 km 3 . Our multi-method approach allowed us to establish that the deposit stems from one colossal event at 3.2 ka and to reconstruct the processes that dominated each phase of the rock avalanche. Our research contributes significantly to understanding not only the Kandersteg event but also complex emplacement processes and mechanics of large rock slope failures.