New study proves Earth’s core wobbles

Scientists’ understanding of the Earth’s inner core has expanded dramatically over the past three decades. In a new study, published in Science Advances, a team of researchers from the University of Southern California (USC) College of Letters, Arts and Sciences found that the inner core oscillates, contradicting previously proposed models that suggested it consistently rotates at a faster pace than the Earth’s surface.

By analyzing seismic data, experts found that the inner core changed direction over the six-year period from 1969 to 1974 — a phenomenon that also explains the variation in day length that has been shown to fluctuate persistently over the past few decades.

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“From our findings, we can see changes on the Earth’s surface compared to its inner core, as people have claimed for 20 years,” said study co-author John E. Vidale, professor of Earth Sciences at USC. . “However, our latest observations show that the inner core rotated a little slower from 1969-71 and then moved in the other direction from 1971-74.” We also observed that the length of the day grew and shrank, as would be predicted. The coincidence of these two observations makes the oscillation the likely interpretation.”

By analyzing seismic waves generated by Soviet underground nuclear bomb tests from 1971 to 1974 in the Arctic Novaya Zemlya archipelago, Professor Vidale and his colleagues found that the inner core was rotating more slowly than previously predicted (approximately 0.1 degrees per year). ). Applying the same methodology to a couple of previous atomic tests under Amchitka Island at the tip of the Alaskan archipelago, the researchers were surprised to find that the inner core had reversed direction, changing at least a tenth of a degree per year.

“The idea that the inner core oscillates was a model that was up in the air, but the community was divided on whether it was viable,” explained Professor Vidale. “We went into this expectation of seeing the same rotation direction and rate in the previous pair of atomic tests, but instead we saw the opposite.” We were quite surprised to find that she was moving in the other direction.” These findings support the hypothesis that the inner core oscillates based on variations in day length (plus or minus 0.2 seconds over six years) and geomagnetic fields.

“The inner core isn’t fixed — it’s moving under our feet, and it seems to move back and forth a few kilometers every six years. One of the questions we’re trying to answer is: does the inner core move progressively or is it mostly locked up compared to everything else in the long run? We are trying to understand how the inner core formed and how it moves over time — this is an important step towards better understanding this process.”