Every 35 years, an unusual phenomenon occurs in the Earth’s core

Decades of earthquake data reveal that since 2010, the Earth’s inner core has been rotating at a slower pace than its mantle and surface, according to a recent scientific study.

The research seems to support the contentious discovery from last year that the Earth’s inner core might have reversed its rotation in relation to the mantle and surface, a phenomenon that could happen approximately every 35 years. Additionally, a recent study indicates that an unknown factor may have affected the most recent reversal.

The study underwent peer review and was published in the journal Nature on June 12.

Researchers analyzed data from earthquakes occurring at the same location but at different times between 1991 and 2023 near islands in Antarctica. Seismic waves generated by these quakes traveled through Earth’s interior, with some passing through the inner core, and were detected on the opposite side of the planet.

Scientists examine quake waveforms over months or years. If the inner core rotates independently of Earth’s other layers, seismic waves would traverse varying parts of it. Should the hypothesis of rotational direction changes in the inner core hold true, identical waveforms would be observed before and after such a shift.

Among 200 comparisons, researchers identified 25 matches, indicating a potential change in the rotation direction of the inner core relative to the mantle around 2008.

John Vidale, a geophysicist from the University of Southern California and lead author of the study, concurred with the findings of the controversial 2023 study after reviewing the progression of quake waveforms over time.

Seismologist Lianxing Wen from Stony Brook University remains skeptical of earlier findings, despite Vidale’s results. According to Science News, he suggests that the inner core’s expansion and contraction could account for the research outcomes.

“The changes are substantial enough to alter the waveforms of recurring earthquakes,” states Wen.

Geophysicist Hrvoje Tkalčić of the Australian National University believes that the reality may be a middle ground between the perspectives of Vidale and Wen.

“We need more information to find the ultimate truth,” Tkalčić said.

Vidale suggests that if the rotation direction of the core changes within the expected time frame, it is likely to revert to its previous pattern shortly. Roughly two decades ago, the inner core appeared to rotate quite rapidly for a period, and this phenomenon is anticipated to recur in the near future.

“By monitoring it over the next five to ten years, we will likely gain a clearer understanding of the events that transpired,” Vidale states.