Volcanomagnetic evidence of the magmatic intrusion on 13th May 2008 Etna eruption

During the onset of 2008 volcanic crisis at Mt Etna, the near‐real time magnetic data provided a continuous updating of the volcano activity state on the northern flank. On the morning of 13 th May 2008, significant local magnetic field changes marked the resumption of the eruptive activity characterized by the opening of a fracture field on the northern flank, and an eruptive fissure in the Valle del Bove. In agreement with the northward propagation of seismic events, magnetic signals at 5 stations in the summit area revealed a nearly NNW‐SSE oriented magmatic intrusion, which started at about 9:00 GMT, propagated northward for about 2 km, and stopped at 14:00 GMT before reaching the North‐East Rift. Magnetic variations, with amplitude ranging between 1.8 nT and −6.5 nT, are consistent with those calculated from piezomagnetic models, where stress‐induced changes in rock magnetization are produced by the magmatic intrusion.