Scientists have made a surprising new discovery: the inner core of the Earth – a solid metallic mass deep beneath the liquid outer core – is not only changing its rotation speed but may also be deforming.
John Vidale, a geophysicist at the University of Southern California in Los Angeles, presented this finding at the American Geophysical Union meeting on December 9. This discovery could shed light on the long-standing debate about the changes occurring at the center of the Earth.
The inner core of the Earth is not only changing its rotation speed but may also be deforming. (Illustrative image).
Since direct examination of the Earth’s core is not possible, scientists rely on studying seismic waves from earthquakes. They typically monitor quakes occurring in the South Sandwich Islands near Antarctica, which are opposite measuring stations in Alaska. Seismic waves travel through the Earth like sound waves through water, with some waves passing through the inner core before reaching Alaska.
In the new study, Vidale’s team analyzed about 200 pairs of earthquakes that occurred from 1991 to 2024. They found subtle differences in the waveforms recorded in Yellowknife (Canada) that did not appear in Fairbanks (Alaska). This suggests that the surface of the inner core is deforming.
Various hypotheses have been proposed by scientists. It is possible that the entire inner core is deforming, like a rugby ball changing shape. Alternatively, only certain areas on the surface may be bulging or contracting, forming “dents” and “bulges.” These changes could be due to gravitational forces from the mantle – the largest layer inside the Earth – or due to material movement in the outer core.
Xiaodong Song, a geophysicist at Peking University and one of the first to discover differences in the rotation of the inner core compared to the rest of the Earth, expressed agreement with Vidale’s findings. He noted that while the differences in waveforms are primarily due to changes in rotation, other processes such as surface deformation may also be occurring simultaneously. “It’s not just choosing one or the other,” he remarked.
Vidale concluded that, although scientists have yet to determine how these changes will affect life on the Earth’s surface, they continue to study this phenomenon to gain a better understanding.
