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Conference Paper

The formation of a circular collapse crater at Rhonegletscher (Switzerland)

Authors

Bauder,  Andreas
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Ogier,  Christophe
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Hodel,  Elias
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Werder,  Mauro
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Hösli,  Leo
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Räss,  Ludovic
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Walden,  Jane
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Jacquemart,  Mylène
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

Farinotti,  Daniel
IUGG 2023, General Assemblies, 1 General, International Union of Geodesy and Geophysics (IUGG), External Organizations;

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Citation

Bauder, A., Ogier, C., Hodel, E., Werder, M., Hösli, L., Räss, L., Walden, J., Jacquemart, M., Farinotti, D. (2023): The formation of a circular collapse crater at Rhonegletscher (Switzerland), XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG) (Berlin 2023).
https://doi.org/10.57757/IUGG23-3880


Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5020666
Abstract
The formation of circular collapse craters are frequently observed on many receding tongues of formerly active glaciers. In absence of substantial ice flow dynamics, subglacial cavities formed by meltwater conduits are no longer closed down but continuously enlarge. A local depression will form at the surface due to creep with decreasing roof thickness. This process is accompanied by the formation of circular crevasses. Complete loss of stability eventually will lead to the collapse of the entire surface leaving a crater in the ice behind. Understanding the physical processes and conditions governing the collapse crater dynamics is essential to assess processes of rapid glacier retreat and hazards resulting from snout collapses and sudden blockage of subglacial drainage pathways.On the glacier tongue of Rhonegletscher such an evolution was detected in spring 2022. A monitoring was carried out between June and October in bi-weekly to monthly intervals with drone surveys to document the surface topography, survey of network of ice flow markers and GPR surveys to estimate cavity size. After a successful drilling through the roof, direct measurements of roof thickness and cavity height were conducted in the evolving cavity. Preliminary ice flow modelling results show strain patterns that coincide with the observed low-angle circular crevasses. Although initiated by the presence of a subglacial drainage conduit, our results suggest the mechanical failure of ice lamellas from the cavity roof as main driver of the collapse crater, and subglacial melting by air flow or water drainage as minor influence.