Abstract
THE temperature distribution in the Earth's core places important constraints on the Earth's internal heat budget and on models of the geodynamo. The solid inner core crystallizes from a liquid outer core, consisting mainly of iron alloyed with a lighter element, at a depth of about 5,100 km (corresponding to a pressure of about 3.3 Mbar). Thus, the most reliable means of determining the temperature gradient in the core is to estimate the melting temperature of iron and iron-rich compounds at the pressure of the inner core boundary. Current estimates range from about 4,000 to 8,000 K; but these estimates, obtained from shock compression1–3, theory (discussed in ref. 4) and extrapolation of static pressure data2,3,5, are poorly constrained. Here I present melting-point measurements on iron and iron–oxygen compounds at static pressures of up to Mbar. Extrapolation of these results to 3.3 Mbar yields a temperature at the inner-core boundary of 4,850±200 K. A weak change in optical absorption observed above 2,000 K may correspond to the solid–solid phase transition found in shock experiments at 2 Mbar (ref. 1).
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Boehler, R. Temperatures in the Earth's core from melting-point measurements of iron at high static pressures. Nature 363, 534–536 (1993). https://doi.org/10.1038/363534a0
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DOI: https://doi.org/10.1038/363534a0
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