The rotation of Earth’s solid inner core may have recently stopped and is reversing, according to a study published in Nature Geoscience this week. These findings show that changes in rotation can occur on a decadal scale and could help our understanding of how processes deep within the Earth affect its surface.
The inner core of the Earth is separated from the rest of the solid Earth by the liquid outer core, which allows it to rotate differently from the rotation of the Earth itself. The rotation of the inner core is driven by the magnetic field generated in the outer core and balanced by the gravitational effects of the mantle. By knowing how the inner core rotates, one can understand how these layers interact. However, the rate of this rotation and whether it varies is debated.
Yi Yang and Xiaodong Song analyzed the difference in waveform and travel time of seismic waves from nearly identical earthquakes that have traveled through Earth’s inner core on similar paths since the 1960s. They found that since about 2009, paths that had previously shown significant temporal variation showed little change, suggesting that the rotation of the inner core had stopped. They also found that it may be related to a reversal of the rotation of the inner core as part of a seven-decade oscillation with a previous tipping point occurring in the early 1970s. The authors point out that this variation correlates with changes in geophysical observations of the Earth’s surface, such as the magnetic field and length of day.
The authors conclude that this fluctuation in the rotation of the inner core, coinciding with periodic changes in the Earth’s surface system, demonstrates the interaction between the different layers of the Earth.
Add Comment