Thermal effects during magma ascent in conduits

Because of strong coupling between viscosity and temperature, the dynamics of magma flows in conduits are drastically controlled by thermal effects due to heat generation by viscous dissipation and loss to the walls by conduction. Here we present analytical solutions and a practical procedure based on an order of magnitude analysis that permits the characterization of the regime and estimation of the main features of the flow. The ranges of validity of analytical and asymptotic solutions were bounded by using results from fully two-dimensional (2-D) numerical solutions of mass, momentum, and energy equations for magma flow inside a cylindrical conduit and the heat conduction in the surrounding host rocks. The results permitted the identification of three regimes: a conductive-heat-loss-dominated regime, an intermediate regime, and a viscous-heating-dominated regime. Some useful analytical parameterizations are proposed for estimating friction in simplified 1-D models. Temperature layering due to heat loss by conduction can lead to local crystal growth and magma solidification whereas heat generated by viscous dissipation can be responsible for crystal resorption and remelting of wall rocks.