Coupled Core-Mantle Thermal Evolution and the History of the Geodynamo

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EAR-0309218NimmoThe evolution of the Earth's core is one of the most fundamental topics in geophysics, relating as it does to the processes of planetary accretion and differentiation; the history of mantle and core temperatures; and the generation of the Earth's magnetic field. This proposal plans to combine geodynamo theory, mineral physics data and mantle convection calculations (both parameterized and numerical) into an integrated model. Model results will be compared with observations and inferences of core and mantle behaviour over time to to investigate the following questions. (1) Is core potassium required to fit the observations? (2) How old are the inner core and the geodynamo? (3) What is the role of mantle compositional layering and plate tectonics in determining geodynamo activity?For each question care will be taken to assess the robustness of the results in view of the uncertainties.The proposal seeks to link the often separate fields of geodynamo studies and mantle convection. Furthermore, because one effect of the geodynamo is to deflect the solar wind, the proposed investigation will have implications for the early implantation and loss of terrestrial atmospheric species. Charged particles mutate or kill primitive organisms, so the early history of the geodynamo is also relevant to the origin of life. Improved models of geodynamo evolution are equally applicable to other silicate bodies, many of which possess or once possessed comparable dynamos. The study should thus have a broad impact across the geological and planetary science community. It also promotes international collaboration and will foster the educational development of one or several undergraduates.