Based on experiments iron melting curves carried out in the 1990s, the temperature of the Earth's core was thought to be around 5000°C.
New research carried out by a collaborative team from the CEA, European Synchotron Radiation Facility and the Institute of Mineralogy and Physics now estimates that the centre of the Earth is actually 1000°C hotter than previously predicted.
Earth’s core is structured: a solid inner core, mainly composed of iron surrounded by a liquid outer core. The temperature at the inner core boundary is expected to be close to the melting point of iron at 330 GPa – the estimated pressure at the core.
This new study presents data from experiments carried out using static laser-heated diamond anvil cell experiments. The anvil, which essentially compresses tiny samples of iron between two synthetic diamonds, can operate at pressures up to 200 GPa. The team then bombarded the iron nuclei with X-rays to investigate the transition from solid iron to molten iron. The data was then extrapolated to give data for the higher pressure ranges, giving a temperature of 6000°C.
This technique gives more insight into the behaviour partially molten iron however the team concedes, there may be a possibility that iron undergoes a further phase change at pressures in excess of 200 GPa, which may change the extrapolated temperature.
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