Scientists looked at seismic waves to learn secrets of the Earth's inner core.
A research team used earthquake-reading technology to discover the Earth's inner core actually has an inner core of its own, the University of Illinois at Urbana-Champaign reported.
"Even though the inner core is small - smaller than the moon - it has some really interesting features," said study leader Xiaodong Song, a professor of geology at the U of I. "It may tell us about how our planet formed, its history, and other dynamic processes of the Earth. It shapes our understanding of what's going on deep inside the Earth."
Seismic waves allowed the researchers to peer under the Earth's surface; an earthquake is like a "hammer striking a bell," a phenomenon that allowed researchers to "listen" and collect a coherent signal of the Earth's coda.
"It turns out the coherent signal enhanced by the technology is clearer than the ring itself," Song said. "The basic idea of the method has been around for a while, and people have used it for other kinds of studies near the surface. But we are looking all the way through the center of the Earth."
In the past, researchers thought the Earth's core was a solid ball of iron, but the recent study reveals the existence of an "inner-inner core" about half the diameter of the inner core itself. The iron crystals present in the outer layer of the inner core are aligned north to south, but in the inner-inner core these crystals point east to west. These findings suggest the inner-inner core could be made up of a different type of crystal.
"The fact that we have two regions that are distinctly different may tell us something about how the inner core has been evolving," Song said. "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 findings were published in a recent edition of the journal Nature Geoscience.
