Earth’s renegade inner core may have ‘paused’ and reversed, scientists say

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Earth's renegade inner core may have 'paused' and reversed, scientists say

Deep earth may be slowing its roll.

Earth’s solid iron inner core appears to be spinning at a slower rate than the planet, according to a new study — but no worries, scientists believe it’s been changing speeds and directions for eons.

The 9,400 degree inner core — discovered in 1936 by studying waves from earthquakes — has a radius of about 746 miles and is roughly 70% of the size of the Moon, according to NASA.

The inner core is beneath the planet’s molten iron and nickel inner core — and the churning relationship between the two generates currents that maintains Earth’s magnetic field, scientists believe.

The “planet within a planet” has been shown to move at its own pace; speeding up, slowing down and rotating, and a new study suggests the inner core might be operating on a 70-year cycle.


A picture shows the structural layers of Earth.
A new study suggests the Earth’s inner core changes speeds and directions on a seven decade cycle.
Getty Images/iStockphoto

An analysis of seismic waves generated by US nuclear tests in 1969 and 1971 found the inner core was rotating more slowly than the Earth, according to the scientific journal Nature.

After 1971, the inner core began to speed up, rotating faster than the planet’s mantle. But around 2009 it had apparently synched up with the rest of the planet before slowing down and possibly reversing — spinning westward instead of eastward, the direction of the planet’s rotation.

Its recent “pause” and possible “seven-decade oscillation” was discovered by Yi Yang and Xiaodong Song, seismologists at Peking University in Beijing, who reported their findings in Nature Geoscience Monday.

The eastward to westward spin cycle is expected to restart around 2040, the study predicted.

Song was one of the first scientists to suggest Earth’s inner core was spinning faster than its crust, according to The Washington Post.

“The inner core is the deepest layer of Earth, and its relative rotation is one of the most intriguing and challenging problems in deep-earth science,” Song told the outlet.

The researchers said the core’s cycle was linked to changes in the length of day — which have been mysteriously getting longer and shorter by microseconds — and the planet’s magnetic field.

A “long history of continuous recording of seismic data is critical for monitoring the motion of the heart of the planet,” said Yang and Song.

The study was not universally heralded in the scientific community.

Lianxing Wen, a seismologist at Stony Brook University, told the news outlet he doesn’t believe the core is rotating independently and said it’s more likely that changes to its surface over time are producing different seismic data.

“This study misinterprets the seismic signals that are caused by episodic changes of the Earth’s inner core surface,” Wen reportedly said. He also said the notion it was slowing down and shifting directions “provides an inconsistent explanation to the seismic data even if we assume it is true.”

University of Southern California seismologist John Vidale reportedly favors a shorter, six-year oscillation model of the inner core.

“No matter which model you like, there’s some data that disagrees with it,” Vidale told The New York Times, which noted some scientists think the inner core is simply wobbling about.

“Because of its inaccessibility, this abyssal realm may forever elude explanation. It’s certainly possible we’ll never figure it out,” Vidale said, adding he was optimistic a consensus could be reached.

Additional research to unlock the mysteries of the core is dependent on the waves created by earthquakes and nuclear blasts, making continuous research unpredictable.

The inner core is “a planet within a planet, so how it moves is obviously very important,” Song told The Times.

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