New research by two scientists at Peking University in Beijing, China, suggests that Earth's inner core may have slowed or possibly reversed its rotation during the past decade.

On Tuesday, Jan. 24, the study was published in Nature Geoscience.

Shift in Rotation

According to the South China Morning Post (SCMP), geophysicists' findings indicate that the Earth's inner core undergoes an oscillation once every seven decades. This correlates with changes in the length of the day, the Earth's magnetic field, and the average temperature and volume of the oceans throughout the world.

The researchers concluded that the Earth appears to operate as a resonant system that incorporates all the primary layers of the solid Earth, from the surface to the deep core. 

An associate research scientist at the SinoProbe Laboratory and the Institute of Theoretical and Applied Geophysics, Yang Yi, said that their study of data spanning six decades demonstrated that the inner core of the Earth was pretty steady between 1964 and 1980.

The inner core spun faster than the Earth until 2009, when it paused. Yang claimed the inner core had been rotating slower than the Earth, reversing its rotation.

The authors assert that a rotation reversal had previously been detected in the early 1970s, suggesting a possible six- to the seven-decade cyclical pattern.

The study discovered comparable oscillations in geomagnetic, day length, global mean sea levels, and temperatures spanning 60-70 years.

Song Xiaodong, chair professor of earth and space sciences at Peking University and co-author of the paper, said their results demonstrated the deep core of the globe was intimately linked to changes in the Earth's surface, such as in sea level and temperature.

Although the whole planet spins once every 24 hours or so, its inner core rotates slower than the rest of the planet.

About 2,900 km (1800 miles) below the surface is where you will find the iron alloy that makes up the Earth's core. The Earth's solid inner core, with a temperature of around 5,200 degrees Celsius, spins inside the globe, separated from the solid mantle by a liquid outer body.

SinoProbe Laboratory head scientist Dong Shuwen indicated that the institution actively sought government financing for future deep earth research initiatives.

"Digging into the Earth is harder than exploring space and the deep sea. The crust is rock-hard. We need to rely on geophysics to learn about the interior," Dong stated.

See Also: Foucault Pendulum: Here's the 171-Year-Old Invention that Proves the Earth Rotates and Spins

Earthquake Data

Seismic waves produced by earthquakes powerful enough to reach the inner core were the focus of the latest investigation by experts.

The group combed through both digital and paper data on earthquakes that occurred all around the globe between the 1980s and 2021.

Due to the similarity in waveform between seismic waves generated by repeated earthquakes, researchers were on the lookout for tremors that had occurred in the same area at various periods.

In contrast, the waves change shape and speed as they pass through the Earth's inner core. The scientists may then estimate the inner core's rotating mode from variations in the waveform patterns.

Yang said that they would evaluate additional data to investigate the predicted seven-decade oscillation in its entirety.

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