Deep beneath Earth’s surface, the inner core—a solid metal sphere encased in a molten outer layer—may be undergoing dramatic changes. Scientists suggest it is not only slowing its rotation but also reshaping its structure, raising fresh questions about the planet’s mysterious centre.

For decades, Earth’s inner core has intrigued scientists, with seismic waves offering rare glimpses into its hidden realm. New findings suggest that the core’s behaviour is far more complex than previously thought.
At a recent meeting of the American Geophysical Union, geophysicist John Vidale from the University of Southern California revealed that the inner core, which appeared to slow its rotation or even reverse around 2009, may also be deforming. The core’s surface could be shifting in shape, akin to a football being reshaped or developing subtle bumps and indentations.
This discovery stems from an analysis of earthquake waves—specifically, twin tremors or “doublets” recorded in Alaska and Canada between 1991 and 2024. Researchers observed subtle differences in waveforms, particularly those recorded in Yellowknife, Canada, which grazed the core’s exterior. These variations point to possible changes in the shallow inner core, including surface swelling or contraction over time.
“The simplest explanation is deformation to the shallow inner core,” Vidale remarked, adding that such changes may be influenced by the gravitational pull of the Earth’s mantle or the dynamic flow of material in the molten outer core.
However, not all researchers agree on the findings. Lianxing Wen, a geophysicist at Stony Brook University in New York, argues that surface changes alone could account for the observed data. “Patches of the inner core’s surface may rise or subside by hundreds of metres per decade, possibly due to material exiting the inner core as it cools,” Wen explained. He, along with Xin Zhang from the University of Science and Technology of China, maintains that the core does not rotate independently of the rest of the planet.
Geophysicist Xiaodong Song of Peking University, a pioneer in the study of the core’s differential rotation, supports Vidale’s findings but suggests that both rotation and surface changes may be occurring simultaneously. “It’s not either or,” he commented.
While these changes in the core might not directly affect life on the surface, scientists caution against dismissing potential long-term impacts. “We don’t know that this is going to affect anything on the surface,” Vidale said. “But we can’t say for certain until we figure out what’s happening.”
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For now, Earth’s inner core remains an enigma, shifting and evolving, while continuing to captivate researchers trying to understand the secrets beneath our feet.
 

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