LOS ANGELES: Researchers from the University of Southern California (USC) have confirmed that Earth’s inner core is rotating more slowly than the planet’s surface, a discovery that could impact both the stability of Earth’s magnetic field and the length of our days, according to a report from Science Alert. This groundbreaking study, published in Nature, reveals that the inner core began decelerating around 2010, marking the first such occurrence in nearly 40 years.
The inner core, a super-hot, dense sphere composed of iron and nickel, resides more than 4,800 kilometers beneath the Earth’s surface. For this study, John Vidale and his colleagues analyzed seismic data from 121 repeating earthquakes recorded between 1991 and 2023 in the South Sandwich Islands region, along with data from Soviet nuclear tests conducted between 1971 and 1974 and other historical nuclear tests by France and the United States.
“When I first saw the seismograms that hinted at this change, I was stumped. But when we found two dozen more observations signaling the same pattern, the result was inescapable. The inner core had slowed down for the first time in many decades,” said Vidale, Dean’s Professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences.
Vidale explained that the inner core’s deceleration is influenced by the turbulent movement of the surrounding liquid outer core, which generates Earth’s magnetic field, as well as gravitational forces from dense regions in the overlying rocky mantle. This slowdown could potentially alter the planet’s rotation, leading to slightly longer days.
“The backtracking of the inner core may alter the length of a day by fractions of a second,” Vidale noted. “It’s very hard to notice, on the order of a thousandth of a second, almost lost in the noise of the churning oceans and atmosphere.”
The research team aims to further investigate the trajectory of the inner core to better understand the reasons behind its shifting movement. “The dance of the inner core might be even more lively than we know so far,” Vidale said.
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