SUMMARY
Small-scale buried structures in volcanic environments could present an extreme relevance, due to their link to the eruptive activity of individual monogenetic edifices, but require, to be detected, a high-resolution geophysical imaging. In such context, the Electrical Resistivity Tomography is often able to recover primary knowledge about the heterogeneity of the buried layers, despite the reduced investigation depth. In this paper an example of such matter is proposed, concerning the Posillipo hill, in the southeastern sector of the Campi Flegrei Caldera (Italy), where an electrical resistivity survey has been carried out in the roman age Seiano tunnel. In such a way, details of the Trentaremi tuff cone buried structure have been revealed, with a maximum depth of exploration of about 100 m. The obtained results have been compared with geological observations on the exposed rocks, interpreting their underground continuation. The geophysical image reconstructs the inner structure of the Trentaremi cone. At the same time, its relationships with respect to the deposits belonging to Neapolitan Yellow Tuff eruption have been highlighted. Reconstructing this stratigraphic sequence, indications about the past volcanic dynamics have been obtained, presenting valuable implications for the future activity forecasting.