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 6 minutes

The motion of the inner nucleus has been a topic of debate within the scientific community for two decades. Some research suggests that the inner core rotates faster than the planet's surface.

But now, a new USC study proves it unequivocally The inner core began to slow down around 2010, They move slower than the Earth's surface.

“When I first saw the seismograms indicating this change, I was puzzled.” said John Vidal, dean of the School of Geosciences at the USC Dornsife College of Letters, Arts and Sciences. “But when we found twenty additional 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 deceleration and deceleration

The inner core is upside down and moving backwards relative to the planet's surface Because it is moving a little slower 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.

With a size equivalent to the size of the moon, The inner core lies more than 4,828 kilometers below our feet and presents a challenge for researchers: It is impossible to visit or see it. Scientists need to use seismic waves generated by earthquakes to create representations of the movements of the inner core.

Seismic ray paths and location of events.  a, PKIKP and PKP beam paths from the SSI source region to the two grids (ILAR and YKA).  The sampled IC region is characterized by a representative 1.5 Hz Fresnel region 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 colored source locations based on focal depth.  Credit: Nature (2024).
Seismic ray paths and location of events. a, PKIKP and PKP beam paths from the SSI source region to the two grids (ILAR and YKA). The sampled IC region is characterized by a representative 1.5 Hz Fresnel region 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 colored source locations based on focal depth. Credit: Nature (2024).

A new look at the iterative approach

Contrary to other research, Vidal and Wei Wang, from the Chinese Academy of Sciences, Repetitive waveforms and earthquakes are used. Repeated earthquakes are seismic events that occur at the same location and produce identical seismograms.

In this study, The researchers compiled and analyzed seismic data recorded around the South Sandwich Islands from 121 repeat 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.

According to Mr. Vidal, The slowing down of the inner core is due to the movement of the outer core of liquid iron that surrounds it, which generates the Earth's magnetic field. As well as the gravitational forces exerted by dense areas of the overlying rocky mantle.

Impact on the Earth's surface

The effects of this change in the movement of the inner core of the Earth's surface can only be speculated on. According to Vidal, The bounce of the inner core can modify the length of the day by a few milliseconds: “It is so difficult to notice that within a millisecond, it is almost lost in the din of the ocean and the boiling atmosphere.”

Future research by USC scientists aims to trace the path of the inner core in more detail In order to reveal the exact reasons for its development.

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“The inner dance of the heart could be more vibrant than we know yet.” Mr. Vidal said.

Article reference:

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

Stan Shaw

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