Studies of seismic waves (generated by earthquakes) indicate that the earth’s inner core may not be such a solid sphere as previously thought. Interaction with the liquid outer core generates a rotational movement that affects the inner core and makes its surface more viscous. It was already known that in the past, the inner core spun faster than the rest of the earth and it is now spinning slower. Now, researchers from the University of Southern California may have discovered why. The answer could lie in interactions between the deepest parts of the planet, almost 5,000 kilometers below the surface. Viscous deformations of the inner core may explain seismic waves that have baffled geophysicists until now, recorded in 121 pairs of earthquakes that occurred at 42 locations near the Sandwich Islands in southern Antarctica between 1991 and 2024. It was also known that the outer core was turbulent, but not to the extent that it has an impact on its neighbor, the inner core (Nature Geoscience, February 10).
