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Research in Geodynamics and Mineral Physics |
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A wide spectrum of research activities deals with the dynamics and physical properties of Earth's interior as well as those of other terrestrial planets and moons. Convective motions in a planet's solid lithosphere-mantle system and liquid outer core are the key dynamical processes that determine its evolution over geological time and are linked to a range of surface observables from fields such as seismology, geology, geomagnetism, geochemistry, and geodesy.
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Several aspects of mantle-plate system dynamics, ranging from the regional scale (individual features or regions) to the global scale, are being studied using two- or three-dimensional numerical models constrained by observations. Regional scale models are being applied to understand the stress distribution in slabs, the ascent of plumes and their interaction with the lithosphere, the formation of ultra-low-velocity zones (ULVZs) above the core-mantle boundary, the recent evolution of the lithosphere and upper mantle under the western USA and Yellowstone region, and lithosphere-mantle dynamics of the India-Asia collision. At the global scale, geochemical geodynamics is a major theme, with the trace- and major-element evolution of planets being studied using using convection models that self-consistently incorporate chemical differentiation by melting, and plate tectonics (for Earth) or stagnant lids (for other planets). In this way, the formation or destruction of geochemical reservoirs can be studied, and chemical signatures compared to geochemical observations. The geodynamics group has a dedicated computational facility including a 48-CPU parallel Beowulf cluster and a computer lab with visualization workstations.
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Experiments in the new fluid dynamics laboratory at UCLA will utilize powerful diagnostic techniques to make quantitative measurements of simulated flows in planetary cores. The results will test long-held theories regarding the properties of convection in core fluids and provide a detailed characterization of flow dynamics at nearly planetary parameter values. Acoustic Doppler velocimetry will be used to study convection in opaque liquid metals, which have properties similar to core fluids. In addition, the optical technique of particle image velocimetry (PIV) will be used to study flows in rotating spherical shells of water, in a set-up that mimics core dynamics and geometry. PIV will provide quantitative measurements of the flow fields that are the essential components of planetary dynamos, but have not been measured adequately by experimental means. Together, these state-of-the-art techniques will provide benchmarks for numerical and theoretical studies of core convection and planetary dynamos. They will also generate the highest resolution experimental convection data to date for interpreting observations of the deep Earth and the planets.
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The mineral physics group is studying how the microscopic-scale structure of minerals influences their physical and chemical behavior, which, in turn, determines planetary scale processes such as mass transport and chemical evolution. The experiments at UCLA center around a diamond anvil cell, a labtop device that offers access to the very high pressures and temperatures relevant to planetary interiors while allowing the experimenter to "see" what happens to the material. Using this, atomic scale processes, high temperature thermodynamics, and transport properties of planetary materials are being examined. Experiments are also performed at large-scale synchrotron facilities such as the Advanced Photon Source in Chicago, which supply an intense x-ray beam that can be used to examine a variety of properties of materials inside the diamond cell, including phase stability, crystal structure, and mineral volume and how they change with pressure and temperature. The resulting thermodynamic and thermoelastic properties are then combined with geophysical and geochemical models to build a coherent picture of Earth and planets' evolution, current state, and possible future.
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Related Sites:
UCLA Geodynamics Web Site
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