Unstable Alpine Permafrost: a potentially important Natural Hazard - Boreholes in Permafrost: Internal Structure, Monitoring and Modelling

 

Quantitative characterisation of Alpine permafrost requires reliable information on the temporal and spatial variations of temperature and deformation. These quantities can be determined with long-term observations in boreholes and a monitoring network installed on the Earth's surface. Such monitoring were carried out on creeping permafrost of the Muragl rock glacier, the test site of the geotechnical/geophysical/glaciological mini-Poly-project devoted to studying the mechanical behaviour of Alpine permafrost.

The principal objective of this project is an improved general understanding of the genesis and mechanical behaviour of rock glaciers, an important geomorphological form of Alpine permafrost. Specific targets of the investigations include:

• core inspection and analyses,
• determination of in-situ physical properties by means of borehole logging, and
• estimation of temporal and spatial variations of temperature and deformation

of the Muragl rock glacier. Monitoring and modelling efforts achieved in the framework of this project may provide substantial contributions to understanding the dynamic reaction of creeping permafrost to climatic variations.

In addition to temperature and deformation monitoring, borehole logging and core analyses have been performed. Their results provide useful information about the current state of strain and will be used to calibrate the results of the geophysical cross-hole tomography. Finally, numerical modelling of the initiation and decay of geomorphological features, such as the transverse ridges that are often observed on rock glaciers, were carried out. Since these ridges are related strongly to the general flow pattern of rock glaciers, and are also observed in regular glaciers, opportunities exist for comparisons between the behaviour of both phenomena. These numerical modelling results will form an important contribution to the understanding of the mechanical behaviour of Alpine permafrost.