Surprised scientists confirm that the rotation of the Earth’s inner core has slowed down: the consequences

A picture of the Earth’s layers and its core. Credit: University of Southern California
Francisco Martin Leon

Francisco Martin Leon Spain meteorite 5 minutes

he Movement of the inner nucleus This has been debated by the scientific community for two decades, and some research suggests so The inner core rotates faster than the planet’s surface.

but now, A new USC study Provides unequivocal evidence of this The inner core started slowing down around 2010moving more slowly than the Earth’s surface.

“When I first saw the seismograms indicating this change, I was puzzled,” he said. John Vidal, dean of Earth Sciences in the USC Dornsife College of Letters, Arts and Sciences. “But when we found twenty other observations pointing to the same pattern, the conclusion was inevitable.

The inner core has slowed down for the first time in several decades. “Other scientists have recently advocated similar and different models, but our latest study provides the most convincing solution.”

Relative to backup and slowdown

It is considered so The inner core reflects and retracts Relative to the planet’s surface because it moves slightly slower and not faster than the Earth’s mantle For the first time in about 40 years. Compared to its speed in previous decades, the inner core is slowing down.

The inner core is a solid ball of iron and nickel surrounded by a liquid outer core of iron and nickel.

about the size of the moon, The inner core is more than 4,828 km away Under our feet and poses a challenge to researchers: It cannot be visited or seen. Scientists must use seismic waves generated by earthquakes to create representations of the motion of the inner core.

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Seismic ray paths and event locations. a, PKIKP and PKP beam paths from the SSI source region to the two arrays (ILAR and YKA). The IC region sampled by a representative 1.5 Hz Fresnel region is marked with dashed circles centered around the PKIKP etch points in the ICB. In the inset, the PKP beam paths (PKP(AB), PKP(BC)), PKiKP(CD) and PKIKP(DF). B, Map of the SSI region with source locations colored by focal depth. Credit: Nature (2024).

A new vision for an iterative approach

Vidal and Wei Wang of the Chinese Academy of Sciences used Frequent waveforms and earthquakes Unlike other investigations. Repeated earthquakes are seismic events that occur at the same location to produce identical seismograms.

In this study, researchers collected and analyzed Seismic data recorded around the South Sandwich Islands Of the 121 recurrent earthquakes that occurred between 1991 and 2023. They also used data from dual Soviet nuclear tests between 1971 and 1974, as well as repeated French and American nuclear tests. Nuclear testing is another basic internal study.

Vidal said so The slowing down of the inner core was caused by the churning of the surrounding outer core of liquid ironwhich generates the Earth’s magnetic field as well as the gravitational forces of dense areas of overlying mantle rock.

Impact on the Earth’s surface

Archaeology From this change in the movement of the inner nucleus Because the surface of the Earth can only be predicted. Vidal said that the retreat of the inner core could occur Changing the length of the day in fractions of a second: “It’s so hard to notice, within a thousandth of a second, that you’re almost lost in the noise of the ocean and the churning atmosphere. “

Future research by USC scientists aims to map out the trajectory of the inner core in more detail to reveal exactly why it changed.

The dance of the inner heart could be more vibrant than we know yetVidal said.

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Wei Wang et al. Internal core rollback by seismic waveform change reflectionsNature (2024). doi: 10.1038/s41586-024-07536-4

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