The formation of Mount Etna as the consequence of slab rollback

Mount Etna, the largest volcano in Europe, lies close to the subduction-related Aeolian magmatic arc but shows no trace of subducted material in its magmas. Mount Etna is also situated on continental crust yet shows oceanic basalt affinities1,2,3, with isotopic ratios of helium and carbon suggesting that it is fed by the same type of mantle source as are mid-ocean ridge basalts4,5. Here we propose that although this giant volcano is not subduction-related—in the sense that it is not part of the magmatic arc—its formation is strongly related to the nearby subduction process. Based on a three-dimensional model of the tectonic plates in this region, we propose that the voluminous melting under Mount Etna results from ‘suction’ of asthenospheric material from under the neighbouring African plate. Such lateral flow is expected when descending slabs migrate backwards in the mantle (rollback) leaving low-pressure regions behind6,7 them. This was previously identified at the northern end of the Tonga arc (southwest Pacific Ocean) where such flow feeds arc8 or backarc9 magmatism. Here we show that in the south Tyrrhenian subduction zone, slab rollback pulls asthenospheric material much farther along the plate contact, reaching the base of the crust in the forearc region. This explains the voluminous melting under Mount Etna and also the recent uplift of the forearc region (the Calabrian peninsula)10.