Mechanics of Magma Chamber with the Implication of the Effect of CO2 Fluxing

Abstract

As the magma ascends from its depth of generation to the surface, it is often stored in a series of chambers along the way. The rheological contrast between the viscous magma in the magmatic chambers and the surrounding rocks disturbed the stress field which can give rise to various modes of rock failure at magmatic pressures less than the lithostatic stress, leading to an eruption. Different modes of mechanical failure of the chamber walls are considered depending on the geometry and the sign the relative pressure. Relaxation of viscous stress around magmatic chambers, which is important on the time scale of weeks to months is considered in the analysis of stability with application to both large and extra-large magmatic chambers such as Yellowstone. The effects of a strong deep CO2 flux in Yellowstone are considered in detail. The analysis shows that variations in the flow rate around the observed mean value of 40 kg/m2/yr in the hydrothermally active areas can change the composition of the magma for several hundred thousand years, and cause periodic uplift and subsidence of the caldera surface with a period of several decades.