Geographic scientists found out, that moon-size inner core rotates faster than its surface by about 0.3 to 0. 5 degree per year. This finding is expected to end a nine-year debate.
The claim that Earth's inner core was getting ahead of itself seemed odd at first. But some computer simulations showed the molten-iron outer core dragging the inner core around by the magnetic field generated in the outer core.
Still, seismologists had problems with measurements of the inner core's excess spin. Now the researchers found persuasive evidence that the inner core really is spinning faster than the rest of the planet, according to Xinhua.
"Extraordinary claims require extraordinary proof," said Xiaodong Song, a professor of geology at the University of Illinois at Urbana-Champaign and co-author of a paper to appear in the Aug. 26 issue of the journal Science. "We believe we have that proof."
Earth's iron core consists of a solid inner core about 2,400 kmin diameter and a fluid outer core about 7,000 km in diameter. The inner core plays an important role in the geodynamics that generates Earth's magnetic field, and an electromagnetic torque from the geodynamics is thought to drive the inner core to rotate relative to the mantle and crust.
The original finding was based on analysis of three decades of seismological records. Scientists have both confirmed and questioned the theory in the intervening years. Some scientists said the original finding could be a flaw in the data.
Song, Richards, and colleagues' evidence is based on side-by-side comparisons of seismic waves from 18 pairs of earthquakes that were nearly identical in location and magnitude. They differed only in date, and such similarity diminishes the margin for error, National Geographic informs.
The temblors occurred in the South Sandwich Islands near Antarctica and were detected by seismometers near Fairbanks, Alaska. On their pole-to-pole journey, the seismic waves traveled through the Earth, some through the inner core.
"Essentially, the waves that traveled through the area outside the inner core—the crust, the mantle, the outer core—are all the same," Song said. "Only when they travel through the inner core are they different."