Electrical Signals Generated by Pyroclastic Density Currents at Stromboli Volcano

Electrical activity, including visible lightning, has been observed at Stromboli (Italy) during various eruptive scenarios and has also been reported in association with the emplacement of pyroclastic density currents (PDCs). The multiparametric monitoring network operating at Stromboli enables a detailed investigation of PDCs generated by a range of eruptive and gravitational processes, including column collapse during paroxysmal eruptions, crumbling of lava overflows, and collapses of the crater rim or flank. Previous analyses of the electrical activity at Stromboli have primarily focused on paroxysmal eruptions during which PDCs concurrently occurred, making it difficult to isolate and interpret electrical signatures generated by PDCs alone. PDCs generated by gravitational instabilities of volcaniclastic deposits, located on the crater rim or volcano flanks, offer a unique opportunity to investigate their electrical signatures in the absence of an eruptive column and other relevant syn-explosive processes. Here, we present analyses of electrical signals recorded during the occurrence of deposit-derived PDCs propagating along Sciara del Fuoco. Electrical activity was measured using a lightning detector deployed in close proximity to the flow pathway to monitor changes in the ambient electric field. Complementary thermal and visual imaging of the crater area and flow path enables correlation of the electrical signal variation with the timing, evolution, and spatial extent of the PDC events. We compare these observations with electrical signals recorded during eruptive activity at Stromboli involving sustained eruptive columns, to assess the similarities and differences between column-collapse PDCs and eruption-driven electrical signatures. Distinguishing different types of volcanic phenomena solely based on their electric signature offers a complementary approach for volcano monitoring, enabling the rapid detection of PDC occurrence and aiding the classification of explosive activity.