Landslides as proxies of climate change: evidence fro past activity records in the Dolomites (Italy).

This study concerns the relationships between climate changes and hillslope evolution during the Late Quaternary, with particular attention to landslide processes. The research has been carried out in test areas located in the Dolomites (Italy), following the basic idea that modifications in landslide frequency may be interpreted as changes in the hydrological conditions of the slopes, which are in turn controlled by climate. By analysing a large data set, consisting of 75 radiocarbon dates, obtained with reference to 24 landslides, temporal clustering of dated mass movements have been observed, that is a necessary condition to look for possible causes of past activity periods. By analysing the data set, four periods of enhanced landsliding have been outlined. These four periods have been compared with different Late Glacial and Holocene paleoclimatic records, in order to check the correspondence between temporal concentrations of landslide events and climatic events. Besides the intrinsic difficulties in the correlation among these records, which are mainly due to different spatial scales (local, regional and global), to dissimilar time-resolutions and dating constraints, remarkable evidence comes forward. The periods of enhanced slope instability in the Dolomites display a quite good correlation with cold and humid phases. At the same time, also periods of dry climate have a clear influence on landslide activity, resulting in gaps in the time series. The results suggest that landslide activity could have been climatically-driven and that, in particular, a positive moisture balance could have played a major role in conditioning slope instability at the hundred to thousand years time scale.