Impacts of post glacial rebound on landsliding at a regional scale in Northern Iceland (Skagafjörður): spatial distribution and mechanisms involved

International audienceParaglaciation has often been considered as a main predisposing factor in landslide occurrence; its consequences have been particularly well identified at a fine scale (especially on bedrock jointing). However, the impacts of paraglaciation on hillslope dynamics at a regional scale have never been discussed. We focus here on the Skagafjörður area (Northern Iceland) to compare the role of paraglaciation with that of classic factors (topography, lithology etc.) in landslide occurrence, using a spatial analysis (based upon a chi-square test). The results highlight that landslides are over-represented in areas where post-glacial rebound was at its maximum (i.e. there is a concentration of landslides in the northern part), which fits well with the first chronological benchmark we obtained. Thus, landslides occurred during the first half of the Holocene, when the post-glacial uplift was at its maximum. Finally, the mechanisms that link post-glacial rebound and landsliding are discussed. On the one hand, post-glacial rebound is identified as an efficient process to generate slope instabilities, leading to a concentration of landslides in the northern part of the fjord. On the other hand, the expected role of glacial debuttressing cannot be demonstrated here, although it is often considered one of the most important paraglacial influences on landsliding