Effect of Viscous Dissipation on Nonisothermal High-Viscosity Magma Flow in a Volcanic Conduit

A two-dimensional nonisothermal model of magma flow in a volcanic conduit is proposed. The model makes it possible to investigate the effect of the processes of viscous dissipation and heat conduction on the magma flow. It is established that the effect of these processes is significant, particularly in the case of high flow rates. It is shown that in this case the conduit resistance calculated from the Poiseuille formula widely used in one-dimensional models is highly overestimated. This is related to the formation of a strongly heated fluid layer with reduced viscosity in the near-wall conduit zone. Within the framework of the proposed model it is possible to describe eruptions with flow rates which are several times higher than the flow rates obtained within the framework of one-dimensional models.