Earth's inner core may be changing its spin and its shape

Changes to seismic waves travelling through the planet could reveal unusual activity in Earth's core

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It’s not unusual for Earth’s core to change its rate of rotation or even its shape over time — though, as far as scientists could tell, never simultaneously. But new research reveals that something unexpected may be happening deep beneath our feet.

Scientists have long debated the cause of strange changes to the seismic waves triggered by earthquakes when they ripple through the planet’s core. One side argued the core’s rotation rate delays or accelerates the travel time of the waves, while the other claimed that it’s deformation of the inner core causing changes in the waves. In the new study, published in journal Nature Geoscience, scientists from China and the US reveal that it’s likely to be both.

The research shows that, in 2010, Earth’s inner core went from rotating faster than the rest of the planet, to slower. This — along with changes near the surface of the inner core — likely interrupted the seismic waves. Like X-rays as they pass through our flesh and bones, these waves allow scientists to ‘see’ what’s happening inside the planet. The researchers think the discovery could help us unlock more information about the core’s properties and structure.