Earth’s inner core may be slowing down and changing shape, new study shows

Research indicates that Earth’s solid inner core, a metallic sphere enclosed within a molten outer core, may undergo changes in both rotation and surface composition. Studies involving seismic waves generated by earthquakes have shown that the rotation of the core relative to the Earth’s surface may have slowed, stopped, or even reversed about 15 years ago. The new findings, presented by geophysicist John Wiedel of the University of Southern California during a meeting of the American Geophysical Union, suggest that additional changes may also be occurring on the surface of the inner core.

Earthquake waves reveal inner core dynamics

Insight into the inner core depends on seismic waves generated by earthquakes, as no instruments can reach the Earth’s core directly. According to reports, geophysicists often investigate seismic waves originating from the South Sandwich Islands near Antarctica. These waves cross the Earth, pass through its layers and reach recording stations such as Alaska. Waveform discrepancies between similar earthquakes occurring at different times indicate changes within the inner core.

Surface change and deformation hypotheses

Reportedly, Vidal and his team analyzed seismic data from nearly 200 earthquake pairs recorded between 1991 and 2024. Anomalies in the waves were observed in recordings from Yellowknife, Canada, but not from Fairbanks, Alaska. Wiedel attributed these differences to possible distortion of the outer surface of the inner core. According to reports, the entire core may be microscopically reshaped or local areas may swell or shrink. These changes may be influenced by gravitational interactions with the mantle or material flows within the outer core.

Diverse Perspectives on Basic Behavior

Interpretations continue to be debated. Geophysicist Lianxing Wen of Stony Brook University suggested in a statement that surface changes alone, without rotational differences, could explain these observations. Meanwhile, Xiaodong Song of Peking University emphasized in his statement that both rotational and surface changes could be contributing factors.

As noted in the reports, the current findings are limited in their implications for the Earth’s surface. Until further research elucidates the processes, potential effects remain uncertain.