Scientists at University College London today revealed a novel way of attacking an age old question; how hot is the Earth's core? The new approach, they say, has major implications for understanding the dynamics of the Earth.
"Its crucial to know the temperature of the Earth's core", explains Professor David Price of UCL's Department of Geological Sciences and co-author of the work reported in the September 30 issue of the journal NATURE.
"There's tremendous heat energy stored down there. The heat flowing out of the core causes earthquakes, volcanoes and the drift of continents. It also causes the turbulent swirling motion of liquid iron in the core that creates the Earth's magnetic field. But if you don't know the core temperature you just can't understand how this all works."
According to the UCL team, the key to the problem is to find out the melting temperature of iron at the stupendous pressure in the core. The team reasoned that the core , consisting mainly of iron, turns from solid to liquid form near the Earth's centre. Experimenters realised long ago the key role of the melting temperature and made heroic efforts to recreate core pressures and temperatures in the lab and watch iron melt in these conditions, but their results remain controversial.
The new line of attack comes from exploiting the power of massively parallel computers. Professor Mike Gillan, a theorist in UCL's Physics and Astronomy Department and a co-author of the NATURE report, explains;
"By using the basic laws of physics you can model any material as a collection of atoms and calculate the melting temperature - and anything else you want - completely from scratch. This basic idea is revolutionising many areas of science, but to do it for iron was a terrific challenge. Because of the huge computer power needed it has never been tried before and without the Cray T3E computer at Manchester this work would have been impossible."
The UCL team reports an iron melting temperature 6500 degrees centigrade - about the temperature of the Sun. They point out though that the Earth's core not being made of pure iron will have a temperature a touch lower - probably 5500 degrees centigrade.
The idea that we are sitting on top of a seething mass of molten iron as hot as the Sun may be pretty scary", remarks Mike Gillan.
"But scientifically the core temperature is important because it is a crucial piece of the jigsaw in understanding how the Earth changes over time. You have to know this if you want to understand earthquakes on a fundamental level. "
Professor Gillan concluded;
"This is only the start. The computational approach will help us understand in detail what the Earth is made of which, in turn, has major implications for the way the solar system was formed."
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Notes to Editors.
(i) "The Melting Curve of Iron At The Pressures of the Earth's Core from Ab Initio Calculations", D.Alfe, M.J.Gillan & G.D.Price will appear in the 30 September edition of NATURE.
(ii) Authors are available for interview by contacting UCL Media Relations on the number above.
(iii) The research was funded by a grant from the Natural Environmental Research Council (NERC).
Journal
Nature