The rotation of the Earth’s inner core slowed down

Deep in the heart of our planet Something amazing is happening. Scientists have discovered that the Earth’s inner core, a solid sphere of iron and nickel with a radius of about 1,220 kilometers, is slowing down. This is according to new research by a team from the University of Southern California (USC), which provides evidence that the inner core began to slow down around 2010, moving more slowly than the Earth’s surface. It’s official. The core rotates more slowly than the surface of the planet.

Confirmed: The rotation of the Earth’s inner core has slowedMid-Journey / Sarah Romero

Conclusive evidence

The Earth’s inner core is a region that remains one of the least understood but most interesting parts of our planet It plays a vital role Whether in the composition of Earth’s magnetic field (our planet’s magnetic field is generated by the movement of the outer core of liquid iron surrounding the solid inner core, for example), or in the tectonic activity or general dynamics of our planet.

“When I first saw the seismograms indicating this change, I was puzzled,” explained University of Southern California earth scientist John Vidal. “But when we found twenty other observations pointing to the same pattern, The result 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.”

Is it slowing down? What does this mean?

This discovery raises important questions about planetary mechanics and could affect the stability of Earth’s magnetic field and the length of our days. This change in the Earth’s inner core may lead to longer days. Although it would not be something perceptible to ordinary humans, because the consequences would be in extra milliseconds (on the order of thousandths of a second). “It’s so hard to notice that, on the order of a millisecond, it’s almost lost in the noise of the churning oceans and atmosphere,” Vidal says.

By looking at seismic data from recent decades recorded around the South Sandwich Islands on 121 recurring earthquakes that occurred between 1991 and 2023, as well as data from dual Soviet nuclear tests between 1971 and 1974, and other internal baseline studies. Regarding frequent earthquakes, they are very interesting because They originate from the same location and produce identical seismic wave patterns (seismograms), Giving a firm basis for the study of the Earth’s interior.

It moves slower than the Earth’s surfaceMid-Journey / Sarah Romero

Scientists discovered that the inner core started slowing down around 2010, and that’s what’s happening now moves backwards, Something that subtly affects the Earth’s rotation in space. But the truth is that the inner core is slowing down compared to its speed in previous decades; It reflects and recedes relative to the planet’s surface.

Why is it slowing down?

The exact reason for the slowdown of the inner core is still unclear, but the researchers believe They propose two hypotheses: 1) The turbulent movement of the outer core of liquid iron, which is responsible for generating the Earth’s magnetic field, exerts a pulling force on the inner core, slowing down its rotation; Or 2) gravitational interactions with denser regions of mantle rock above the outer core could pull on the inner core, further contributing to its slowdown.

For many years, many scientists believed that the inner core rotated faster than the Earth’s surface.Mid-Journey / Sarah Romero

What will happen now? The team now wants to trace the path of the inner core in more detail to reveal exactly why it is changing and determine whether any of these hypotheses are correct, since the rotation of the inner core is an important factor in the process of… Geodynamo Generated by the Earth’s magnetic field and any changes can affect the strength and stability of the magnetic field, which protects the planet from harmful solar radiation. Let’s remember that a stable magnetic field is necessary to maintain the atmosphere and sustain life on Earth. Currently, it is almost impossible to predict what effects this modification will have, but this discovery opens a new avenue of research, providing a deeper understanding of the Earth’s complex inner core.

“The dance of the inner heart could be more vibrant than we know so far,” Vidal concludes.

This can change the length of the day by fractions of a secondMid-Journey / Sarah Romero

References:

  • Wei Wang, Jun E. Fidel, Junying Pang, Keith D. Cooper, Ruyan Wang. Fundamental rollback by reflections of changing seismic waveforms. Nature, 2024; doi: 10.1038/s41586-024-07536-4
  • Wang, W., and Vidal, J. (2022). Seismic observation of the Earth’s oscillating inner core. Scientific Progress, 8. https://doi.org/10.1126/sciadv.abm9916.
  • Sumita, I., and Bergman, M. (2022). Inner core dynamics. Earth’s core. https://doi.org/10.1016/B978-0-444-53802-4.00143-3.
  • Yang, Y., and Song, X. (2020). Temporal changes in the inner core from globally distributed recurrent earthquakes. Journal of Geophysical Research: Solid Earth, 125. https://doi.org/10.1029/2019JB018652.
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