Science & Technology Earth’s inner core may have stopped turning and could go into reverse, study suggests

THE rotation of Earth’s inner core may have paused and it could even go into reverse, new research suggests.

The Earth is formed of the crust, the mantle and the inner and outer cores. The solid inner core is situated about 3,200 miles below the Earth’s crust and is separated from the semi-solid mantle by the liquid outer core, which allows the inner core to rotate at a different speed from the rotation of the Earth itself.

With a radius of almost 2,200 miles, Earth’s core is about the size of Mars. It consists mostly of iron and nickel, and contains about about one-third of Earth’s mass.

In research published in the journal Nature Geoscience on Monday, Yi Yang, associate research scientist at Peking University, and Xiaodong Song, Peking University chair professor, studied seismic waves from earthquakes that have passed through the Earth’s inner core along similar paths since the 1960s to infer how fast the inner core is spinning.

What they found was unexpected, they said. Since

The rotation of Earth’s core may have paused, scientists in China have suggested

2009, seismic records, which previously changed over time, showed little difference. This, they said, suggested that the inner core rotation had paused.

“We show surprising observations that indicate the inner core has nearly ceased its rotation in the recent decade and may be experiencing a turning-back,” they wrote in the study.

“When you look at the decade between 1980 and 1990 you see clear change but when you see

2010 to 2020 you don’t see much change,” added Song.

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. Knowing how the inner core rotates could shed light on how these layers interact and other processes deep in the Earth.

However, the speed of this rotation, and whether it varies, is debated, said Hrvoje Tkalcic, a geophysicist at the Australian National University, who was not involved in the study,

“The inner core doesn’t come to a full stop,” he said. The study’s finding, he said, “means that the inner core is now more in sync with the rest of the planet than a decade ago when it was spinning a bit faster.”

“Nothing cataclysmic is happening,” he added.

Song and Yang argue that, based on their calculations, a small imbalance in the electromagnetic and gravitational forces could slow and even reverse the inner core’s rotation. They believe this is part of a seven-decade cycle, and that the turning point prior to the one they detected in their data around 2009/2010 occurred in the early 1970s.

Tkalcic, who is the author of “The Earth’s Inner Core: Revealed by Observational Seismology,” said the study’s “data analysis is sound.” However, the study’s findings “should be taken cautiously” as “more data and innovative methods are needed to shed light on this interesting problem.”

Song and Yang agreed that more research was needed.

STUDYING THE EARTH’S CORE

Tkalcic, who dedicates an entire chapter of his book to the inner core rotation, suggested the inner core’s cycle is every 20 to 30 years, rather than the 70 proposed in the latest study. He explained why such variations occur and why it was so difficult to understand what happens in the innermost reaches of the planet.

“The objects of our studies are buried thousands of kilometers beneath our feet,” he said.

“We use geophysical inference methods to infer the Earth’s internal properties, and caution must be exercised until multi-disciplinary findings confirm our hypotheses and conceptual frameworks,” he explained

“You can think of seismologists like medical doctors who study the internal organs of patients’ bodies using imperfect or limited equipment. So, despite progress, our image of the inner Earth is still blurry, and we are still in the discovery stage.” (CNN)

THE slice of ocean squeezed between Florida and the Bahamas is one of the well-studied marine environments in the world, and yet it’s also the epicentre of a lasting geological mystery.

Since at least the 1930s, scientists in the region have noticed strange, billowing white clouds appearing in the turquoise tranquillity of the water’s surface.

The curious phenomenon is called a ‘whiting event’, and scientists still don’t understand why it occurs in the Bahamas.

It has become a sort of ‘white whale’ for researchers at the nearby University of South Florida (USF).

The perplexing patches of lightcoloured ocean are sometimes noticed in other oceans and lakes worldwide, but in the Bahamas, they pop up more often than usual.

Direct sampling of the cloudy waters suggests they contain high concentrations of carbonate-rich particles.

Much of the Bahama archipelago sits on a submerged platform of carbonate known as the Bahama Banks. Does this mean sediments are rising to the surface? Or could it be that blooms of phytoplankton are actually producing the suspended material?

No one knows the answers to those questions, but scientists at USF are determined to find out. They’ve used satellite images from NASA to show how whiting events ebb and flow in the Bahamas.

The team doesn’t know if the trends they’ve identified are natural or human-caused, but what they do know is that from 2003 to 2020, the size of these whiting events seemed to correlate with the seasons.

The largest patches occurred from March to May and October to December. On average, the white patches were about 2.4 square kilometers a piece. On a day with clear skies, satellite images usually snapped about 24 of them, covering a total area of 32 square kilometers (12 square miles).

Between 2011 and 2015, however, the patches suddenly swelled in size, covering more than 200 square kilometers of the ocean at their peak (77 square miles). By 2019, however, the patches shrunk again, although they never got quite as small as they had previously been.

The findings suggest a 10-year cycle might be at play. But a cycle of what exactly?

“I wish I could tell you why we saw that peak in activity, but we’re not there yet,” says USF oceanographer Chuanmin Hu.

“We do see some interesting relationships between environmental conditions, such as the pH, the salinity of water, and the behavior of winds and currents, but we can’t yet say what exact mechanical, biological, or chemical processes were responsible for that peak in activity.”

More direct field experiments are needed, and not just in the Bahamas. Comparing whiting events in other regions could help scientists figure out what features they share in common.

USF researchers tested their model on whiting events in the Great Lakes with preliminary success, but now need to back up those patterns on the ground, or rather, in the water.