(CNN) — A new study suggests that the rotation of Earth’s inner core may have stopped and reversed.
Earth is made up of crust, mantle, and inner and outer cores. The solid inner core is located about 5,000 kilometers below the Earth’s crust and is separated from the semi-solid crust by the liquid outer core, which allows the inner core to rotate at a speed other than Earth’s rotation.
With a radius of just 3,500 km, the center of the Earth is approx Size of Mars. It is composed mostly of iron and nickel and makes up about one-third of the Earth’s mass.
A Research Published Monday in the journal Education Natural Earth SciencesYi Yang, an associate research scientist at Peking University, and Xiaotong Zhang, a professor at Peking University, have studied seismic waves that have followed similar paths through the Earth’s inner core since the 1960s.
The result was unexpected. Since 2009, seismic records, changed over time, have shown little difference. This, they said, stopped the rotation of the inner core.
“We show remarkable observations indicating that the inner core has almost stopped its rotation over the past decade and may be reversing,” they wrote in the study.
“When you look at the decade between 1980 and 1990, you see a clear change, but when you look from 2010 to 2020, you don’t see a big change,” Song added.
The spin of the inner core is driven by the magnetic field generated in the outer core and balanced by the gravitational effects of the mantle. Inner core vortices reveal how these layers and other processes interact deep within the Earth.
However, the speed of this cycle and its variability are subject to debate, says Hrvoje Tkalcic, a geophysicist at the Australian National University who was not involved in the study.
“The inner core doesn’t stop completely,” he said. The study’s finding, he said, “is that the inner core is now more in sync with the rest of the planet than it was a decade ago, when it was spinning slightly faster.”
“Nothing catastrophic happened,” he added.
According to their calculations, Chang and Yang argue that a small imbalance in the electromagnetic and gravitational forces can slow and reverse the rotation of the inner core. They believe this is part of a seven-decade cycle, and that the previous point they found in 2009/2010 occurred in the early 1970s.
“The study’s data analysis is robust,” said Tkalcic, author of the book “The Earth’s Inner Core: Revealed by Observational Seismology.” However, the study’s conclusions “should be taken with caution” because “more data and innovative methods are needed to shed light on this hot topic.”
Chang and Yang agreed on the need for further investigation.
A study of the center of the earth
Tkalcic, who devotes an entire chapter of his book to the cycle of the inner core, suggests that the inner core cycle lasts 20 to 30 years instead of the 70 proposed in a recent study. He explained why these variations occur and why it is so difficult to understand what is happening in the inner regions of the planet.
“The objects of our study are buried thousands of kilometers beneath our feet,” he said.
“We use geophysical inference methods to infer the Earth’s internal properties, and should be cautious until more diverse findings confirm our hypotheses and conceptual frameworks,” he explained.
“Seismologists are often thought of as doctors studying the internal organs of patients’ bodies using limited or imperfect equipment. So, despite advances, our picture of the Earth’s interior remains dim, and we are still in the discovery phase.