According to a study published in Nature Geoscience this week, the rotation of Earth’s solid inner core may have recently halted and could potentially be reversing.

These findings suggest that changes in the rotation of the inner core could occur on a decade-long scale and could provide insights into the ways in which processes deep within the Earth impact its surface.

The Earth’s inner core is distinct from the rest of the solid Earth as it is encased by a liquid outer core, which allows it to rotate independently from the rotation of the Earth as a whole.

The rotation of the inner core is powered by the magnetic field generated in the outer core and counterbalanced by the gravitational pull of the mantle.

Understanding how the inner core rotates could shed light on the interactions between these layers. However, the speed of this rotation and whether it fluctuates is a topic of debate.

Yi Yang and Xiaodong Song evaluated the difference in the pattern and travel time of seismic waves from nearly identical earthquakes that have traversed the Earth’s inner core along similar routes since the 1960s.

They discovered that since around 2009, paths that previously displayed notable temporal changes have shown little variation, indicating that the rotation of the inner core has likely come to a halt.

They also detected that this could be linked to a reversal of the inner core rotation as part of a seven-decade oscillation, with a previous turning point taking place in the early 1970s.

The team notes that this fluctuation aligns with variations in geophysical measurements at the Earth’s surface, such as the magnetic field and the length of the day.

They conclude that this oscillation in the rotation of the inner core, which coincides with periodic shifts in the Earth’s surface system, illustrates the interaction between different layers of the Earth.

Source: 10.1038/s41561-022-01112-z

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