Mass-movement, geologic structure and morphologic evolution of the Pizzotto–Greci slope (Calabria, Italy)

Deep-seated mass-movements of different types affect the Pizzotto–Greci slope in northwest Calabria, Italy. The slope is carved out of phyllitic rocks capped by gneissic layers. Its geological structure is extremely complicated by tectonic structures that pervasively cross the slope transversely and downslope. A large-scale gravitational deformation of sackung type affects the slope. On the upslope side a debris-flow source area feeds a large fan constructed by recurrent debris-flow deposits. Aggradation is consequently occurring along the stream at the base of the slope. er to define the internal structure of the slope for a stability slope model, geological, geostructural, geomorphological, historical and dendrogeomorphologic studies, as well as direct geotechnical logs and indirect geophysical investigations have been carried out over a two-year project financed by the EC Environment Programme. in aspects of the geological and geomorphological studies and some preliminary geotechnical data are presented here, along with a conceptual model aimed at describing the relationships between the mass-movements on the slope and the construction/destruction stages of the fan at the base of the slope. The model is based on the assumption that aggradation has a stabilising effect on the slope, thus debris-flow activity is reduced and, consequently, destruction of the fan occurs, bringing the slope again towards unstable conditions. The reactivation of mass-movement, however, leads to the reconstruction of the fan and the buttressing effect at the base of the slope is restored. Thus, the process is cyclic and self-regulating.