From Argonne Lab: “Doubling Estimates of Light Elements in the Earth’s Core”

Argonne National Laboratory

MARCH 1, 2013
Zhu Mao

The inner core of the Earth is the remotest area on the globe, mostly impossible to study directly. It is an area of the planet that experiences both extremely high pressure ranging from 3,300,000 to 3,600,000 times atmospheric pressure, and extremely high temperatures somewhere from 5000 to 6000 K. One way to study this area is by recording how sound waves travel across the interior, matching these profiles to known information about how sound waves travel through candidate iron alloys, and attempting to discern which materials must be present. This method requires an understanding of how sound waves travel through the potential materials present in the core. A team of researchers utilized APS x-rays to develop a new model of how sound waves travel through iron and iron-silicon alloys, showing for the first time that increased temperatures will affect the sound wave profile, and that sound velocity and density correlate in a non-linear way. Their results suggest that the amount of light elements in the inner core could be two times more than estimated in previous studies without considering these effects.

plots
Velocity-density plots of the samples at high pressures and temperatures. The top panel shows the velocity-density plot for hcp-Fe at both 300 K and 700 K. The dashed lines shows the linear fit, while the solid line shows the power law fit, which matches the data more closely. The bottom panel shows the velocity-density relation of both hcp-Fe and the iron-silicon alloy at 300 K.

earth core

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