| Summary: | International audience The deformation of rock glaciers is a climate-dependent process which affects many mountain debris slopes underlain with ice-rich permafrost (Haeberli et al., 2006). Under temperate conditions, like in the Alps, the typical magnitude of movement is in the order of a few dm/a to 1-2 m/a (Barsch, 1996). However, recent measurements of accelerating rock glaciers show that velocity can increase up to several m/a (Delaloye et al., 2012). This kinematics variability can locally lead to slope instabilities and trigger hazardous phenomena: in France, the collapse of the Bérard rock glacier in 2006 (Bodin et al., 2016) and the debris-flow that started at the Lou rock glacier in 2015 (Paulhe et al., 2015) can be considered as two events that exemplify the possible impacts of permafrost degradation for human societies living in mountain territories. At the limit between the Northern and the Southern-more Mediterranean-influenced-French Alps, the Laurichard rock glacier benefits from a long-term monitoring since the early 80's (Francou & Reynaud, 1992). Using 30-year long annual geodetic surveys of blocks, we detected inter-annual fluctuations of velocity (Bodin et al., 2009), which synchronicity with many series on other surveyed rock glaciers in the Alps suggests that the atmospheric warming, modulated by the nivological conditions, is controlling the rock glacier deformation rates (Delaloye et al., 2012). Nevertheless the knowledge on the processes that govern such behavior is still lacking physical basis: a better understanding requires to model the geomechanics of rock glacier, and for that accurate multi-temporal maps of surface displacements are fundamental. For that purpose, we produced very high-resolution 3D models of the Laurichard rock glacier, acquired either by terrestrial laserscanning (TLS) in 2005, 2006, 2011 and 2013, airborne laserscanning (ALS) in 2012 and terrestrial photogrammetry (or structure-from-motion, SfM) in 2013 and 2015. The density of the generated point clouds we ...
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