Abstract
Jacobs1 proposed that the Earth's inner core is growing through the freezing of outer-core material as the Earth gradually cools2. Recent studies have shown that compositional effects associated with this freezing process can release energy at a rate sufficient to power the geodynamo3,4 and may be crucial in determining the dynamic state of the outer core5. Here we investigate the effects of composition on the freezing process itself, drawing on metallurgical experience, and speculate on the structure and state of the inner core. We propose that the interface separating the inner and outer core is dendritic and argue that the region in which freezing takes place may extend throughout the entire inner core. Consequently the compositionally driven convective motions which stir the outer core and sustain the geodynamo also occur within the interdendritic spaces of the inner core. The seismic evidence which corroborates this proposal is briefly reviewed.
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Fearn, D., Loper, D. & Roberts, P. Structure of the Earth's inner core. Nature 292, 232–233 (1981). https://doi.org/10.1038/292232a0
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DOI: https://doi.org/10.1038/292232a0
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