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The paper presents the case history of San Fratello, a small town in the Nebrodi Mountains in Sicily rich in history and having very peculiar environmental and cultural characteristics. Both slopes of the narrow ridge where San Fratello lies were affected in 1754, 1922, 1986 and 2010 by very large landslides. The landslide of February 2010 is largely the reactivation of that of 1754. It destroyed many infrastructures and seriously damaged more than 200 buildings and caused the evacuation of 25% of the population. Emergency actions to block regression of uphill movements and secure the buildings and their inhabitants as quickly as possible, were carried out. The sliding slope down to the town was left to its natural evolution. The paper presents the results of the geomorphological and geotechnical analyses recently carried out to understand the whole landslide reactivation mechanisms. It is felt necessary to define an advanced geotechnical model of the landslide for quantitative evaluation of hazard and rational landslide risk management in the area.

This paper reports new geochemical data on dissolved major and minor constituents in surface waters and ground waters collected in the Managua region (Nicaragua), and provides a preliminary characterization of the hydrogeochemical processes governing the natural water evolution in this area. The peculiar geological features of the study site, an active tectonic region (Nicaragua Depression) characterized by active volcanism and thermalism, combined with significant anthropogenic pressure, contribute to a complex evolution of water chemistry, which results from the simultaneous action of several geochemical processes such as evaporation, rock leaching, mixing with saline brines of natural or anthropogenic origin. The effect of active thermalism on both surface waters (e.g., saline volcanic lakes) and groundwaters, as a result of mixing with variable proportions of hyper-saline geothermal Na–Cl brines (e.g., Momotombo geothermal plant), accounts for the high salinities and high concentrations of many environmentally-relevant trace elements (As, B, Fe and Mn) in the waters. At the same time the active extensional tectonics of the Managua area favour the interaction with acidic, reduced thermal fluids, followed by extensive leaching of the host rock and the groundwater release of toxic metals (e.g., Ni, Cu). The significant pollution in the area, deriving principally from urban and industrial waste-water, probably also contributes to the aquatic cycling of many trace elements, which attain concentrations above the WHO recommended limits for the elements Ni (not, vert, similar (40 μg/l) and Cu (not, vert, similar (10 μg/l) limiting the potential utilisation of Lake Xolotlan for nearby Managua.