The movement of Earth’s inner core has been a topic of debate in the scientific community for the past 20 years, with some studies suggesting that the inner core rotates faster than the Earth’s surface. However, a new study has presented clear evidence that the inner core started to slow down around 2010 and is now moving at a slower pace compared to the Earth’s surface.
king othersIt shows that Earth’s inner core gradually super-rotated from 2003 to 2008, then repeated a slower rotation 2-3 times along the same path from 2008 to 2023. Image by USC Graphic/Edward Sotelo.
“When I first saw the earthquake records suggesting this change, I was puzzled,” said John Bedale, a professor at the University of Southern California.
“But when we found 24 more observations showing the same pattern, the result was inevitable.”
“The inner core is slowing down for the first time in decades.”
“Other scientists have recently proposed similar or different models, but our latest work offers the most plausible solution.”
The inner core is believed to be rotating and moving relative to the Earth’s surface, as it is now moving slightly slower than Earth’s mantle after about 40 years of moving faster.
Compared to the rates observed over the past few decades, the inner core is now slowing down.
The inner core is a solid iron-nickel sphere surrounded by a liquid iron-nickel outer core.
Located more than 4,828 km (3,000 miles) beneath the Earth’s surface, the inner core is roughly the size of the Moon and poses a challenge for researchers as it cannot be visited or directly observed.
Scientists rely on seismic waves from earthquakes to study the movement of the inner core.
In contrast to previous studies, Professor Vidale and his team used waveforms and repeating earthquakes in their research.
Repeating earthquakes are seismic events that occur in the same location and produce identical earthquake records.
The study analyzed recorded seismic data from 121 repeating earthquakes around the South Sandwich Islands between 1991 and 2023, as well as data from Soviet and nuclear tests from the early 1970s and other studies on the inner core.
“The slowing down of the inner core is attributed to the churning of the liquid iron outer core that surrounds it. This churning creates a gravitational pull from the Earth’s magnetic field and the dense region of the rocky mantle above,” Prof Vidale explained.
“We can only speculate on how these changes in the inner core’s movement will impact the Earth’s surface.”
“The retreat of the inner core could briefly alter the length of the day. This alteration lasts for milliseconds and is almost imperceptible amid the noise of the ocean and atmosphere,” he added.
The study was published in the journal Nature.
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Wang others Retrograde motion of the inner core due to reversal of seismic waveform changes. Nature. Published online June 12, 2024, doi: 10.1038/s41586-024-07536-4
Source: www.sci.news
