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The Earth’s center is 1,000 degrees hotter than previously thought

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Posted April 26, 2013
This artist's view depicts the different layers of the Earth and their representative temperatures: crust, upper and lower mantle (brown to red), liquid outer core (orange) and solid inner core (yellow). The pressure at the border between the liquid and the solid core (highlighted) is 3.3 million atmospheres, with a temperature now confirmed as 6000 degrees Celsius. Credit: ESRF

This artist’s view depicts the different layers of the Earth and their representative temperatures: crust, upper and lower mantle (brown to red), liquid outer core (orange) and solid inner core (yellow). The pressure at the border between the liquid and the solid core (highlighted) is 3.3 million atmospheres, with a temperature now confirmed as 6000 degrees Celsius. Credit: ESRF

Scientists have determined the temperature near the Earth’s centre to be 6000 degrees Celsius, 1000 degrees hotter than in a previous experiment run 20 years ago. These measurements confirm geophysical models that the temperature difference between the solid core and the mantle above, must be at least 1500 degrees to explain why the Earth has a magnetic field. The scientists were even able to establish why the earlier experiment had produced a lower temperature figure. The results are published on 26 April 2013 in Science.

The research team was led by Agnès Dewaele from the French national technological research organization CEA, alongside members of the French National Center for Scientific Research CNRS and the European Synchrotron Radiation Facility ESRF in Grenoble (France).

The Earth’s core consists mainly of a sphere of liquid iron at temperatures above 4000 degrees and pressures of more than 1.3 million atmospheres. Under these conditions, iron is as liquid as the water in the oceans. It is only at the very centre of the Earth, where pressure and temperature rise even higher, that the liquid iron solidifies. Analysis of earthquake-triggered seismic waves passing through the Earth, tells us the thickness of the solid and liquid cores, and even how the pressure in the Earth increases with depth. However these waves do not provide information on temperature, which has an important influence on the movement of material within the liquid core and the solid mantle above. Indeed the temperature difference between the mantle and the core is the main driver of large-scale thermal movements, which together with the Earth’s rotation, act like a dynamo generating the Earth’s magnetic field. The temperature profile through the Earth’s interior also underpins geophysical models that explain the creation and intense activity of hot-spot volcanoes like the Hawaiian Islandsor La Réunion.

Recreating the Earth's liquid iron core in the laboratory: a speck-sized piece of iron is thermally isolated and placed between the tips of two small conical diamonds. Pressing the two diamonds together produces pressures of 2 million atmospheres and more. As a laser beam heats the sample to temperatures of 3000 to 5000 degrees, a thin beam of synchrotron X-rays is used to detect whether it has started to melt. This will change its crystalline structure, in turn modifying the "diffraction pattern" of deflected X-rays behind the sample. Credit: ESRF/Denis Andrault.

Recreating the Earth’s liquid iron core in the laboratory: a speck-sized piece of iron is thermally isolated and placed between the tips of two small conical diamonds. Pressing the two diamonds together produces pressures of 2 million atmospheres and more. As a laser beam heats the sample to temperatures of 3000 to 5000 degrees, a thin beam of synchrotron X-rays is used to detect whether it has started to melt. This will change its crystalline structure, in turn modifying the “diffraction pattern” of deflected X-rays behind the sample. Credit: ESRF/Denis Andrault.

Read more at: Phys.org

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