Rockglaciers

• Main Authors: Schoeneich, Philippe, Bodin, Xavier, Kellerer-Pirklbauer, Andreas, Krysiecki, Jean-Michel, Lieb, G.K.
• Other Authors: Pacte, Laboratoire de sciences sociales (PACTE), Université Pierre Mendès France - Grenoble 2 (UPMF)-Université Joseph Fourier - Grenoble 1 (UJF)-Sciences Po Grenoble - Institut d'études politiques de Grenoble (IEPG)-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry ), Institute of Geography and Regional Science, Karl-Franzens-Universität Graz, Autriche, Université Joseph Fourier - Grenoble 1 - Institut de géographie alpine (UJF IGA), Université Joseph Fourier - Grenoble 1 (UJF), Schoeneich Philippe, Dall'Amico Matteo, Deline Philip., Zischg Andreas
• Format: Book
• Language: English
• Published: HAL CCSD 2011
• Subjects: geo; envir; permafrost
• Online Access: https://hal.archives-ouvertes.fr/halsde-00870999

Rockglaciers are the most prominent features of alp ine permafrost. They are creeping accumulations of debris, moving usually at rates of cm/yr or dm/yr. The observed changes on rock glacier dynamics are all related to velocity changes, and show in most cases an increase in velocity. Depending on the importance of the velocity increas e, the five following types of reaction can be distinguished: * Moderate positive and negative velocity changes, re lated to changes of MAGST with a time lag of one to two years. * Acceleration of rock glacier displacement, with opening of crevasses on the rock glacier surface. * Rupture and dislocation of the lower part of rock g laciers: in several cases, the lower part of the rock glacier starts to move significantly more than the upper part. * Total collapse of the lower part of the rock glacier: the lower part of the rock glacier breaks down as a debris flow and is totally removed * Very strong acceleration of the rock glacier: the a cceleration speeds up to very high values. One case is known so far, were velocities reached values as high as 80 m/yr ! The expected effects of velocity changes can be eit her local and limited to the rockglacier surface, or affect the downslope area : * Veloctiy increase will induce increased damage to i nfrastructures built on rockglaciers. * Strong acceleration will increase the surface instability, and the formation of scarps can lead to local rockfall hazard on the rockglacier surface. * Velocity increase will induce increased rockfall ac tivity on the rockglacier front, as well as a progression of the front. * Partial or total rupture and collapse can occur in a few cases, and threaten potentially large areas downslope. * Where rockglacier fronts are overhanging steep slopes or torrential catchments, secondary processes mobilizing the released debris can induce an increased hazard downslope. The following recommendations can be made in order to reduce hazard due to rockglaciers : * Infrastructures on rockglaciers should be avoided. * The ...