Core of the Earth

Excerpts from article appearing in July 18, '96 San Francisco Chronicle
Inner Core Of the Earth Spins Faster

"We didn't think this was something we could ever hope to measure," said Paul Richards of Columbia University's Lamont-Doherty Earth Observatory, co-author of the paper that was published yesterday in the journal Nature. By tracking the arrival times of waves from 38 earthquakes that rumbled through the Earth between 1967 and 1995, the researchers created what amounts to a sonogram of the inner Earth, similar to medical sonograms used to see inside the human body. Because the speed of waves varies according to the properties of the material it traverses, the scientists were able to create an image of the core. ...

Richards and colleague Xiaodong Song discovered that the moon-size core of the Earth spins slightly faster than the Earth's crust. ... Confirming these results, a paper soon to be published by University of California at Berkeley geophysicists Raymond Jeanloz and colleagues at Harvard got almost exactly the same results using different methods. ...

Song said he was "truly surprised" by the finding, because it contradicts the conventional geophysical mind-set about the inner dynamics of the planet. "We have tended to see the internal structure of the Earth as static," he said. ...

Just as the rotating Earth churns up hurricanes and storms in the atmosphere, currents of iron create similar weather patterns underneath. ... Several theories could explain the core's rapid spin. The solid iron crustal core could be getting spun around like a giant electric motor by the magnetic forces created by the molten iron that surrounds it.