Geologists from the U.S. and China have discovered that the surface of Earth’s inner core is not solid, as previously thought, but rather soft and susceptible to deformation. These changes are driven by processes in the liquid outer core and mantle, which may explain fluctuations in the inner core’s rotation speed. Until now, there was no direct evidence that turbulence in the outer core affects the inner core, noted Professor John Vidale from the University of Southern California.
The discovery was made accidentally while investigating the slowdown of the inner core’s rotation over the past 10–15 years. Analyzing seismic data from U.S. and Canadian stations between 1991 and 2023, researchers identified over 120 earthquakes whose seismic waves reflected off the inner core, revealing structural anomalies.
Further analysis showed that these anomalies were not related to the core’s rotation but to irregularities on its surface that appeared and disappeared rapidly. This is only possible if the outermost layer of the inner core has a soft, viscous structure influenced by processes in the outer core and the lower mantle.
This study confirms that the interaction between the inner and outer core is more complex than previously assumed and may significantly impact Earth’s dynamics, including seismic activity and the planet’s magnetic field.
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