Stratigraphic Methodology for the New Geological Map of Etna Volcano

Abstract

The new 1:50,000-scale geological map of Etna volcano is based entirely on a stratigraphic approach, using three different kinds of stratigraphic units, namely lithostratigraphic, lithosomatic, and synthemic units, which show the complex setting of the spatial and temporal evolution of the volcanic system and the surrounding environment. Lithostratigraphy represented the main stratigraphic criterion used for the identification of the volcanic bodies during the field survey and the cartographic representation. Subsequently, unconformity-bounded units were applied to group lithostratigraphic units into synthems. In addition, lithosomes were used to better represent the spatial localization of different eruptive centres according to their morphology. On the whole, we identified 27 lithostratigraphic units, grouped into 8 synthems and 9 volcanoes. In detail, effusive and explosive deposits generated by each eruption of Mongibello volcano and, in part, Ellittico volcano were mapped in terms of flow rank; for the last 2000 years, these deposits were grouped into three lava-flow time intervals using labels and boundaries that allow each flow to be identified. This stratigraphic framework represents the best current synthesis of the geological evolution of Etna volcano using the main unconformities recognized within its complex volcanic succession. The detailed reconstruction of past eruptive activity allowed the compilation of the most accurate dataset currently achievable, in particular of the Holocene eruptions of Etna volcano, which will significantly improve the assessment of volcanic hazard, together with petrological interpretation of erupted magmas and geophysical modelling of the volcanic plumbing system.