Multiparametric Study of Wind and Atmosphere Effect on Explosive Eruptive Style

Abstract:

The atmospheric environment interacts with volcanic plumes produced by explosive eruptions in a number of ways. The wind field can affect atmospheric air entrainment into the column favouring its buoyancy. Similarly, the structure of the atmosphere and its properties can significantly influence the dynamics of volcanic plumes. In recent years, several numerical simulation tools and observation systems have investigated the action of wind field and atmospheric properties on volcanic column height and bending, revealing an important influence of these variables on plume behavior. A less explored issue is the action of wind and atmospheric properties on the eruptive style, i.e. on the buoyant or collapsing regimes shown by the plume, and the factors controlling the shift from one regime to the other. In this study, we address these issues using a new numerical simulation tool for solving the plume theory equations. This tool, named PlumeMoM (de’Michieli Vitturi et al., in preparation), allows the continuous polydispersity of pyroclastic particles to be described using a quadrature-based moment method, an innovative approach in volcanology well-suited for the description of the multiphase nature of magmatic mixture. Several physical processes and real conditions were considered: loss of mass along the column, entrainment of atmospheric air, vertical profiles of atmospheric temperature and density, and atmospheric stability A global sensitivity analysis of the effects of these parameters on plume dynamics and stability was also performed by coupling the plume model with the DAKOTA statistics toolkit. Results provide a better understanding of the key processes affecting plume regime and identification of the main parameters controlling column behaviour.