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Computational Geodynamics: G. Morra

Many challenges exist in geodynamics, from developing models of Early Earth evolution, to the investigation of the largest Earthquakes, called megathrusts, from the evolution of extra-solar planets, to the evaluation of the conditions for the existence of life on the icy planets of our solar system. At UL Lafayette we develop new numerical techniques simulate these systems and integrate them with the rising amount of data available on our and other planets. Example of recent research projects are:

Role of the Spin-Transition in the Mantle to Earth's evolution. The strength of the Earth's Lower Mantle, extending from ~670 km to ~2880 km depth and that constitutes more than half of our planet, is scarcely known. Recent research has shown that the ferropericlase, a major mantle mineral, changes its spin state around 2000 km depth. This observation has been combined with variations of the viscosity across the lower mantle. Our numerical models help to explain stagnation and mixing of mantle material, and shows that Large Igneous Provinces can be explained by the growth of mantle plume heads crossing the highest viscosity lower mantle region.

Characterizing mantle plumes. Constraints from mineral physics, petrology and geophysics have suggested that the wadsleyite layer (410–520 km depth) at the top of the transition zone can store large amounts of volatiles (e.g. OH, CO). We use our numerical tools to show that plumes spontaneously rise from this region due to the collective motion of hydrated diapirs (here, chapter 5). Our models can explain the mysterious existence of surface volcanism in remote regions such as Central Asia. 

Fast Numerical Modeling for Multiphase-flow. Ample evidence indicates that the degree of violence of volcanic eruptions depends on the complexities of the rising bubbly gas in the volcanic conduit. In particular the regular degassing during Strombolian activity seems to naturally emerge from slugs created by spontaneous collective dynamics of rising gas bubbles. At UL we develop new numerical techniques based on near-field and far-field interaction between particles and diapirs that can reproduce Einstein and Batchelor viscosities, and show how they can be applied to modeling the flow of gas in volcanic conduits, particle sedimentation, wave propagation in heterogeneous media



Gabriele MorraDepartment of Physics, School of GeosciencesUniversity of Louisiana at Lafayette