Abstract
The Earthâs magnetic field is powered by energy supplied by the slow cooling and freezing of the liquid iron core. Efforts to determine the thermal and chemical history of the core have been hindered by poor knowledge of the properties of liquid iron alloys at the extreme pressures and temperatures that exist in the core. This obstacle is now being overcome by high-pressure experiments and advanced mineral physics computations. Using these approaches, updated transport properties for FeâSiâO mixtures have been determined at core conditions, including electrical and thermal conductivities that are higher than previous estimates by a factor of two to three. Models of core evolution with these high conductivities suggest that the core is cooling much faster than previously thought. This implies that the solid inner core formed relatively recently (around half a billion years ago), and that early core temperatures were high enough to cause partial melting of the lowermost mantle. Estimates of coreâmantle boundary heat flow suggest that the uppermost core is thermally stratified at the present day.
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Acknowledgements
C.D. is supported by Natural Environment Research Council (NERC) fellowships NE/H01571X/1 and NE/L011328/1 and a Green scholarship at IGPP. D.G. is supported by NSF grant EAR/1065597 and NERC grant NE/I0 12052/. M.P. is supported by NERC grants NE/H02462X/1 and NE/M000990/1. D.A. is supported by NERC grant NE/M000990/1. The authors thank T. Nakagawa, P. Driscoll, F. Nimmo and S. Labrosse for providing the model results that were used in Fig. 3.
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Davies, C., Pozzo, M., Gubbins, D. et al. Constraints from material properties on the dynamics and evolution of Earthâs core. Nature Geosci 8, 678â685 (2015). https://doi.org/10.1038/ngeo2492
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DOI: https://doi.org/10.1038/ngeo2492
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