Numerical simulations of magma ascent along volcanic conduits

The process of magma ascent along volcanic conduits during explosive eruptions is numerically simulated by solving the transport equations in the one-dimensional, steady, and isothermal assumptions. The physical model considers the non-equilibrium multiphase flow of a mixture of liquid magma, crystals and/or lithic fragments, and exsolving gas. The liquid magma is treated as a mixture of 10 major oxides plus dissolved water and carbon dioxide, and the gas phase as a mixture of water and carbon dioxide. The model is characterized by a strong coupling between fluid dynamic and constitutive equations, whereby the magma properties like viscosity, density, and gas solubility are calculated on the basis of the chemical composition of the liquid magma and its crystal content, and of the physical conditions along the volcanic conduit. The model predictions obtained by considering many different eruptive conditions reveal complex and sometimes non-intuitive relations between the initial conditions and the predicted flow parameter distribution. The composition of the liquid magma and the amount and composition of volatiles are found to be of major importance in determining the dynamics of magma ascent during explosive eruptions. The results of this modeling can be useful to forecast the volcanic hazard at a given volcano, as the conduit exit flow parameters could constitute initial conditions to study the atmospheric dispersion of the gas-pyroclasts and the dynamics of pyroclastic flows.