Geophysicists need to know the temperature at which iron melts at very high pressures in order to understand the structure of the Earth. Both the solid inner core and the molten outer core, which extend to 55% of the Earth's radius, consist mainly of iron. A group of theoretical physicists from the UK has now calculated the melting curve of iron from first principles, and claim that the results are as accurate as those from high-pressure experiments (Nature 401 462).
Dario Alfè, David Price and Mike Gillian of University College London used a Cray T3E supercomputer to calculate that the melting point of iron was 6700 Kelvin, plus or minus 600 Kelvin, at the pressure of the inner core boundary. The inner and outer cores store tremendous amounts of energy as heat. The transfer and movement of this energy can cause earthquakes and volcanoes. It can also influence the motion of continental plates. Moreover, the magnetic field generated by the molten core protects the Earth from the solar wind.
“The core temperature is crucial for our understanding of how the Earth changes over time,” says Mike Gillian. “You have to know this if you want to understand earthquakes on a fundamental level.”
