Deformation and eruptions at Mt. Etna (Italy): a lesson from 15 years of observations

Volcanoes deform as a consequence of the rise and storage of magma; once magma reaches a critical pressure, an eruption occurs. However, how the edifice deformation relates to its eruptive behavior is poorly known. Here, we produce a joint interpretation of spaceborne InSAR deformation measurements and volcanic activity at Mt. Etna (Italy), between 1992-2006. We distinguish two volcano-tectonic behaviors. Between 1993-2000, Etna inflated with a starting deformation rate of ~1 cm yr-1 that progressively reduced with time, nearly vanishing between 1998-2000; moreover, low-eruptive rate summit eruptions occurred, punctuated by lava fountains. Between 2001-2005, Etna deflated, feeding higher-eruptive rate flank eruptions, along with large displacements of the entire East-flank. These two behaviors, we suggest, result from the higher rate of magma stored between 1993-June 2001, which triggered the emplacement of the dike responsible for the 2001 and 2002-2003 eruptions. Our results clearly show that the joint interpretation of volcano deformation and stored magma rates may be crucial in identifying impending volcanic eruptions.