ABSTRACT
The recent geological history of the Ischia Island, emerged portion of the Phlegraean Volcanic District, is closely related to the volcano-tectonic dynamic of the Mt. Epomeo resurgent caldera. The presence of a relatively shallow magmatic body strongly conditioned the geological evolution of the island that is responsible for volcanic activity, crustal deformations and strong seismicity. This magmatic body, located at about 2000 m depth, produces the development of a stable hydrothermal system characterised by high heat flow (200–400 mW/m2) (Cataldi et al. 1991) and several thermal springs and gas vents. In addition, diffuse gravitational processes involved the edge of the resurgent block. The present study focuses on the gravitational deformation of Mt. Nuovo, located in the western portion of Mt. Epomeo, which involves alkali-trachytic pyroclastic flow deposit (Mt. Epomeo Green Tuff (MEGT); Brown et al., 2008) and trachytic and phonolitic lavas (133 ka; Vezzoli, 1988). Historical and archaeological documents led some authors (Del Prete & Mele, 2006) to consider that the deep gravitational phenomenon connected with the formation of Mt. Nuovo is related to a catastrophic volcanotectonic event which took place around 460–470 BC during the last stages of Mt. Epomeo uplift. Based on a multidisciplinary approach, this study proposes a new high-resolution engineering-geological model of the Mt. Nuovo slope, that provides constraints to the ongoing gravitational slope deformation. By means of geomorphological surveys and terrain analyses through GIS, fault scarps, terraces, saddles, trenches and morphological counter-slopes were also identified, thus providing more details and constraints to the geometry of the slope deformation. A geomechanical survey was also carried out to derive the geomechanical properties of the outcropping jointed rock mass and to evaluate their influence on the landslide process.
