Scientists from the University of Southern California (USC) have proven, in a new study, that the Earth’s inner core is slowing down in relation to the planet’s surface. The consequences of this are still unknown, but researchers speculate that the length of days could change. The research was published on Wednesday (12) in the scientific journal Nature.
The rotation of Earth’s inner core has been a topic of debate in the scientific community in recent decades, with some research suggesting that it is faster than the planet’s surface. However, the USC study provides new evidence that in reality the inner core has been slowing its rotational speed since 2010, moving more slowly than Earth’s surface.
For John Vidale, dean professor of Earth Sciences at the USC Dornsife College of Letters, Arts and Sciences, this slowness in nuclear movement can change the length of a day in fractions of a second, but this may be imperceptible.
“It’s very difficult to notice, on the order of a thousandth of a second, almost lost in the noise of the choppy oceans and atmosphere,” he says.
What is the Earth’s inner core and how does it move?
The Earth’s inner core is a solid sphere composed of iron-nickel and is surrounded by a liquid outer core, also made of iron-nickel. It is approximately the size of the Moon and is located more than 4,800 kilometers from our feet and represents a challenge for scientists, as it cannot be visited or viewed. Therefore, scientists use the seismic wave from earthquakes to create representations of the movement of the inner core.
In recent decades, researchers have studied a variety of earthquakes, including repeat earthquakes — seismic events that occur in the same location. This analysis is important to produce identical seismograms (records of ground movements).
For this study, scientists compiled and analyzed seismic data recorded around the South Sandwich Islands from 121 repeating earthquakes that occurred between 1991 and 2023. They also used data from Soviet nuclear tests that occurred between 1971 and 1974, as well as French nuclear tests. and Americans, and tests analyzed by other studies.
According to Vidale, the slowdown in the speed of the inner core was caused by the agitation of the outer core surrounding the inner core. This generates the Earth’s magnetic field, as well as the gravitational “pulls” of the dense regions of the overlying rocky mantle.
“When I first saw the seismograms that suggested this change [desaceleração], I was perplexed”, says Vidale. “But when we found two dozen more observations signaling the same pattern, the result was inevitable. The inner core slowed down for the first time in many decades. Other scientists have recently argued for similar and different models, but our latest study provides the most convincing resolution.”
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