A Multiphysics Approach: Thermodynamics, Material Mechanics And Fluid Dynamics Of Magma Systems At Active Volcanic Regions
Gunn De Rosas, Cathina Leann
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Understanding the genesis, incubation, evolution and equilibration of silicic magma reservoirs that drive and source volcanic activity all over the planet is fundamental to the discipline of geology. The subsurface processes of magma infiltration, transport, alteration and fractionation determine the volumetric rate of crustal production as well as its chemical composition, pluton and batholith formation, the chemical and thermal evolution of the crust and the severity and frequency of volcanic extrusion, flood basalts and ocean ridge volcanism. The excess pressure of the magma system, as it evolves and drives surficial eruption, is a key factor in hazard prediction and mitigation for volcanologists all over the world and has the capacity to save human life and property. In chapter 2, I seek to explore the thermodynamics of a developing magma reservoir in the Earth. I experiment with varying sill thicknesses and emplacement rates of magma into the shallow crust using a multi-physics FEM solver and discuss the most efficient rates of emplacement as well as the significant sill thickness plays in the resultant reservoir volume (magma retaining a temperature > 1150 K) as a function of time. I also explore sensitivity of the model to various thermodynamic parameters in the magma and the crust; namely, thermal conductivity, specific heat capacity and the injection temperature of the magma. I find that sill thickness, contrary to previous work, plays a significant role in the volume of magma reservoirs emplaced at any given geologic rate. In chapter 3, I implement mechanical heterogeneity around a mature magma reservoir to discuss the implications such a zone of modified, heated, crust has on source pressure values in a swelling magma chamber. Previous work at other volcanic centers has shown that treating the crust as a purely elastic medium in these zones inflates the pressure estimates for long-term inflation magnitudes by as much as 400%. I use a multiphysics solver to model fluid flow into a shallow chamber and the resultant mechanical deformation of the surrounding crust with and without the modified elasto-plastic zone and inferred discuss pressure source values for both. I also discuss differences in the uniform pressure distribution of deformation modeled in previous studies at Soufriere Hills Volcano and my magmastatic model. In chapter 4, I explore the dynamics of ascending magma in the feeder-dike system at Soufriere Hills Volcano and develop a method of inverting real-time geodetic monitoring to interpret short-term perturbations in the subsurface of an active volcano. I show that volumetric inflation of the surface can be directly related to pressures in the dike-system, magma flow rates and volatile contents within usefulranges.