Earth’s inner core not only rotates but also oscillates, says new study

Refuting a previously accepted theory, scientists have concluded that Earth’s inner core oscillates and this results in a change in day length. With the Earth’s composition divided into layers, the inner core is found in the center, followed by the outer core, lower mantle, upper mantle crust, and then the atmosphere. It was previously believed that the inner core, which is the hottest part of Earth, rotated faster than the planet’s surface. However, now scientists at the University of Southern California (USC) have noted that over the past decades the inner core oscillates and has changed direction.

The findings were part of a new study published Science Advances. “From our findings, we can see the Earth’s surface in comparison to its inner core, as people have claimed for 20 years,” Told John E. Wiedel, study co-author and dean professor of Earth sciences in the USC Dornsife College of Letters, Arts and Sciences.

Vidale said that the inner core of Earth Slow rotation was found between 1969 and 1971. “We also note that the length of a day will be predicted to increase and shrink,” Videl said. Highlighting the two observations, Wiedel said that the coincidence indicates that the inner core oscillates.

Videl, together with researcher Wei Wang, has used seismic data from the Large Aperture Array (LASA) and observed that the inner core rotates at a slower rate than previously thought. While a 1996 research predicted the movement to be 1 degree per year, the new study estimated it to be 0.1 degrees per year.

Wiedel developed a new beam-making technique and used it to analyze the waves produced by Soviet underground atomic bomb tests from 1971 to 1974. Wang used the same technique to study the waves produced by two nuclear tests conducted off the island of Amchitka.

The scientists further measured the compression waves from the nuclear explosions and noted that the inner core had begun sub-rotating at a speed of one-tenth of a degree per year. These findings also indicated a six-year oscillation through direct seismic observation for the first time. “The inner core isn’t static—it’s spinning under our feet, and it seems to move back and forth a couple of kilometers every six years,” Wiedel said.

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