He inner core movement has been debated by the scientific community for two decades, and some research indicates that the inner core spins faster than the planet’s surface.
But now, a new USC study provides unequivocal evidence that the inner core began to slow down around 2010moving more slowly than the Earth’s surface.
“When I first saw the seismograms hinting at this change, I was stumped.“, said John Vidale, dean professor of Earth Sciences at USC Dornsife College of Letters, Arts and Sciences. “But when we found two dozen more observations pointing to the same pattern, the result was inescapable. The inner core had slowed down for the first time in many decades. Other scientists have recently advocated similar and different models, but our latest study provides the most compelling resolution.“
The relativity of backing up and slowing down
It is considered that the inner core is reversing and retreating relative to the planet’s surface because it moves slightly slower rather than faster than Earth’s mantle for the first time in about 40 years. Relative to its speed in previous decades, the inner core is slowing down.
The inner core is a solid sphere of iron and nickel surrounded by the 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 presents a challenge to researchers: cannot be visited or seen. Scientists must use seismic waves from earthquakes to create representations of the movement of the inner core.
A new vision of a repetitive approach
Vidale and Wei Wang of the Chinese Academy of Sciences used waveforms and repeated earthquakes unlike other investigations. Repeat earthquakes are seismic events that occur at the same location to produce identical seismograms.
In this study, the researchers compiled and analyzed seismic data recorded around the South Sandwich Islands of 121 repeated earthquakes that occurred between 1991 and 2023. They also used data from twin Soviet nuclear tests between 1971 and 1974, as well as repeated French and American nuclear tests. nuclear tests from other inner core studies.
Vidale said that The slowing down of the inner core was caused by the churning of the surrounding liquid iron outer corewhich generates the Earth’s magnetic field, as well as the gravitational pulls of the dense regions of the overlying mantle rock.
The impact on the Earth’s surface
The implications of this change in the movement of the inner core for the Earth’s surface can only be speculated. Vidale said that the retreat of the inner core can alter the length of a day in fractions of a second: “It is very difficult to notice, on the order of a thousandth of a second, almost lost in the noise of the churning oceans and atmosphere. “
Future research by USC scientists aims to chart the trajectory of the inner core in greater detail to reveal exactly why it is changing.
“The dance of the inner core could be even livelier than we know so far“said Vidale.
Reference
Wei Wang et al. Inner core backtracking by seismic waveform change reversals, Nature (2024). DOI: 10.1038/s41586-024-07536-4
This entry was published in News on June 13, 2024 by Francisco Martín León
