Recent research led by the University of Southern California (USC) has revealed an intriguing phenomenon: the rotation of Earth’s inner core has slowed significantly compared to the planet’s surface over the past 14 years.
This discovery, published in the journal Nature, raises new questions about the internal dynamics of our planet and its possible repercussions on the surface. Furthermore, researchers point out that if this mysterious trend continues, it could lengthen the days on Earth, although the effects would be imperceptible to us.
The inner core, a superdense, fiery sphere of iron and nickel about the size of the Moon and located more than 4,800 kilometers below the Earth’s surface, is a difficult object to study. However, it is known that this core is surrounded by another outer core of molten metal and both are encapsulated by the Earth’s mantle, a solid layer of rock. Although the entire planet rotates, the inner core can move at a different speed due to the viscosity of the outer core.
“Unequivocal” evidence that the core has slowed down
For more than two decades, scientists have debated the spin rate of this enigmatic inner core, knowing for 40 years that it tends to spin slightly faster than the crust and mantle. However, the recent study led by John Vidale, professor of Earth Sciences at USC, marks a turning point by showing “with unequivocal evidence” that since 2010 this core has begun to slow down.
“When I first saw the seismograms hinting at this change, I was perplexed,” Vidale said. “But when we found two dozen more observations pointing to the same pattern, the result was inescapable. The inner core had slowed down for the first time in many decades. Other scientists have recently advocated similar and different models, but our latest study offers resolution more convincing,” he added.
To study these movements, scientists like Vidale use seismic waves generated by earthquakes and nuclear tests. In this specific research, data from 121 repeat earthquakes in the South Sandwich Islands and old nuclear tests were analyzed, allowing the team to gain a clearer view of the behavior of the core.
Why does this slowdown occur?
According to Vidale, the results of their study suggest that the change in the rotation speed of the inner core could be influenced by the agitation of the surrounding liquid iron outer core, which is responsible for generating the Earth’s magnetic field, and also by the gravitational forces of the rocky mantle that surrounds it. Despite the complexity of these processes, researchers believe that these movements do not imply an immediate risk of natural catastrophes.
On the other hand, although the consequences of this phenomenon are subtle, the study indicates that it could affect the length of days on Earth. But there is no reason to be alarmed either: the change would only occur in fractions of a second, so small that they would be almost imperceptible, lost in the “noise” of the oceans and the atmosphere, as Vidale explained. In other words, there is no need to set the clocks yet.
“The dance of the inner core could be even more lively than we know so far,” commented Vidale, underscoring the importance of continuing to monitor and study these geological depths.
Felipe Espinosa Wang with information from USC and Nature.
