Scientists Confirm Slowing Rotation of Earth’s Inner Core, First in Decades
Researchers from the University of Southern California (USC) have revealed that the Earth’s inner core is rotating more slowly than the planet’s surface, according to a report by Science Alert. This landmark discovery has significant implications for our understanding of planetary mechanics and could affect both the stability of Earth’s magnetic field and the length of our days.
The study, published in the journal Nature, presents evidence that the inner core’s rotation began to decelerate around 2010. This marks the first such slowdown in approximately 40 years, indicating a change in motion relative to the Earth’s mantle. The inner core, a super-heated and extremely dense sphere composed of iron and nickel, resides more than 4,800 kilometers beneath the Earth’s surface.
To reach their conclusions, John Vidale and his team at USC analyzed data from 121 recurring earthquakes recorded between 1991 and 2023 near the South Sandwich Islands in the South Atlantic. They also examined seismic readings from Soviet nuclear tests conducted between 1971 and 1974, in addition to French and American nuclear tests, to gather comprehensive data on the inner core’s behavior.
“When I initially saw the seismograms indicating this change, I was puzzled,” said Mr. Vidale, Dean’s Professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences. “However, after identifying two dozen more observations showing the same pattern, the evidence was undeniable: the inner core had slowed down for the first time in decades. Although other scientists have proposed various models, our study provides the most compelling evidence for this phenomenon.”
Mr. Vidale attributes the slowdown of the inner core’s rotation to the turbulent movements of the surrounding liquid outer core, which generates the Earth’s magnetic field, and the gravitational influences from denser regions in the overlying rocky mantle. This slowdown could eventually impact the planet’s overall rotation, resulting in a minor extension of the length of our days.
“The effect on day length is incredibly subtle,” noted Mr. Vidale. “We’re talking about changes on the order of a thousandth of a second, barely detectable amidst the noise of the oceans and atmosphere.”
The research team aims to further investigate the inner core’s movement to uncover the precise reasons behind this shift. “The motion of the inner core may be even more dynamic than we currently understand,” Mr. Vidale concluded.
Photo: NASA
