CAREER: Energetics of Mantle Convection and Physics of Earth's Evolution

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This project proposes to improve our understanding of the energetics of convection in Earth's mantle and its relation to the evolution of the Earth system, including the atmosphere, the ocean, and the core. The central theme is the global balance between potential energy release (energy source) and viscous dissipation (energy sink), and in particular, energy dissipation associated with the intense deformation of stiff lithosphere at subduction zones --- probably the most peculiar aspect of plate-tectonic convection. The following two questions form the backbone of the proposed research. How does the mantle actually flow by solid-state creep? Mantle rheology is not only controlled by temperature, pressure, and stress, but also affected by volatile contents, phase transformations, and grain size evolution. And how can we test various theoretical predictions by observations? The PI will study a series of key geodynamical problems through numerical modeling, theoretical analysis, and a compilation of relevant geological observations. The entire research plan is composed of the following seven sub-themes: (1) the ambient state of stress in oceanic lithosphere, (2) the energetics of slab rollback, (3) the onset of convection with internal heating, (4) scaling laws for stagnant-lid convection with mantle melting, (5) the initiation of plate tectonics, (6) the history of ocean volume and global water cycle, and (7) the nature of core-mantle interaction. Collectively, they constitute a major step toward a better understanding of the long-term behavior of Earth, by tackling unresolved first-order issues all together. Moreover, each of them is designed to address a stand-alone, basic physics problem with potential applications beyond the scope of this proposal, reaching out to earthquake seismology, regional tectonics, planetary sciences, Precambrian geology, igneous petrology, plume dynamics, and geomagnetism. This proposal includes the education of one female Ph.D. student in theoretical geodynamics. The PI will also assimilate research results into three existing undergraduate/graduate courses he regularly teaches at Yale. In addition, a new 200-level undergraduate course will be developed on the physics of Earth's evolution, with hands-on experience in scientific computing. The PI will also conduct community outreach through the Yale-New Haven Teachers Institute, to assist K-12 teachers in developing public school curricula, by showing how geophysical topics can be used as friendly examples in science classes.