Numerical modeling of lava flows at Mount Etna: Influence of lava rheology on flow morphology

Numerical modelling is an essential approach for investigating the rheological, thermal, and dynamical processes that control lava flow behaviour. In this study, we present a numerical analysis of lava flows emplaced during the 6–8 December 2015 eruption of Mount Etna, employing a shallow-water-approximation model solved using a finite-volume method. We assess the influence of temperature-dependent, as opposed to isothermal, Newtonian, Bingham, and Herschel–Bulkley rheologies on lava flow morphology, together with the effects of discharge-rate variability, vent location, and the post-eruption phase of flow propagation. The results demonstrate that temperature plays a dominant role in governing lava flow advancement. Thermal Newtonian and Bingham models successfully reproduce the observed flow dynamics and runout distances, whereas the nonlinear Herschel–Bulkley model, with a temperature-dependent power-law index, underestimates the flow extent. Simulated thickness distributions closely agree with field observations, accurately capturing lava accumulation near the vent and at the flow front. By contrast, isothermal models significantly overestimate lateral spreading and fail to replicate the observed emplacement patterns. Post-eruption simulations indicate that cooling controls lava flow evolution following the cessation of effusion, resulting in increased viscosity, flow starvation, and eventual arrest. Sensitivity analyses further reveal that small variations in vent position and discharge-rate distribution can substantially alter lava flow pathways.