Two-dimensional simulations of magma ascent in volcanic conduits

A two-dimensional model for magma ascent in volcanic conduits is presented. The model accounts for the magma rheology, heat flux to the surrounding co untry rock, planar and axisymmetric geometries, and flow in the mushy regio n by means of a continuum mixture formulation that does not require keeping track of the liquid-solid interfaces. Numerical experiments for Newtonian and visco-plastic Bingham rheologies of magmas are presented as functions o f the volumetric flow rate at the dyke's entrance and wall heat fluxes for both round conduits and fissures. It is shown that, depending on the magma rheology, dyke geometry, volumetric flow rate and wall heat flux, the magma may solidify along the original dyke's walls, thus reducing the available cross-sectional area to the flow, or the original dyke's walls may melt. It is also shown that the dyke's wall temperature may first increase and then decrease, and that the axial velocity profile exhibits a parabolic shape i n the core region and a plug zone near the dyke's walls for Bingham rheolog ies. Copyright (C) 1999 John Wiley & Sons, Ltd.