Abstract The southeastern flank of Mt. Etna volcano slides into the Ionian Sea at rates of centimeters per year. While gravitational spreading and tectonic forces can cause volcanic flank collapse, their effects intrinsically trade off with magmatic forcing. There is still strong uncertainty regarding the processes underlying the sliding. Modeling the different forces appears to be the ideal framework to understand flank spreading; however, any model explaining the geological or dynamic features of the volcano must also explain its deformation and seismic patterns, the primary markers of volcanic activity used by monitoring institutions. Here, we present a series of new rheological models using the 3D thermomechanical code of LaMEM. The models include all the primary geological features related to gravitational and tectonic forcing, producing deformation models and observations grounded on geophysical imaging and rock physics experiments. We observed the impact of each implemented geometry and its sensitivity to parameters by comparing the model results to GPS observations quantitatively, estimating the misfit between the model and data using the coefficient of determination. The results demonstrate that the ductile rheology of the rocks under the eastern flank is essential to explain deformation patterns even in the absence of magmatic inputs. The horizontal displacement is controlled by supercritical fluids horizontally constrained by pre‐existing volcanic structures, which act as a lubricant for gravitational sliding. Their connection with deeper magmatic input must be better constrained by modeling magma transients during specific time periods and performing corresponding time‐dependent data analyses.
Bensing et al. (Sun,) studied this question.