Excerpt from cnet.com
Though the seismic waves from earthquakes are best known for their destructive abilities, in the hands of geologists, they can be powerful tools of discovery. A research team at the University of Illinois (UI) has just used the rumbles from quakes to more closely examine the core of our planet, and what they found there was quite a surprise. It seems our Earth’s core has another core that measures about half the diameter of the original core.
What demarcates this “inner-inner core” is that the iron crystals it contains are oriented on an east-west axis, unlike the iron crystals in the “outer-inner core” which organize along a north-south axis.
“The fact that we have two regions that are distinctly different may tell us something about how the inner core has been evolving,” said Xiaodong Song, a professor of geology at UI who, along with visiting postdoctoral researcher Tao Wang, led the team responsible for the discovery. “For example, over the history of the Earth, the inner core might have had a very dramatic change in its deformation regime. It might hold the key to how the planet has evolved. We are right in the center — literally, the center of the Earth.”
The researchers’ findings were published in the journal Nature yesterday.