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Earth's Inner Core Has Stopped Spinning, Is About to Switch Its Direction: Study | Weather.com

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Like clockwork, we wake up every morning, rummage through our supplies to find something to eat and brew that perfect cup of coffee (or tea) that keeps us going the whole day. At first, the same routine day after day isn't that bothersome, but once clouds of monotony begin to cast their shadow, we start seeking change. And thousands of kilometres beneath our feet, Earth's inner core agrees with this human tendency!

Scientists have revealed that the inner core of our planet has slowed down simply because it's tired of circling in the same direction for decades. And now, it's time for a change.

The study by scientists from Beijing's Peking University has revealed that sometime in the past decade, Earth's inner core (which usually spins faster in relation to the mantle) stopped doing so! Instead, it appears to be reversing the direction of its spin.

Diving into the mysteries of the Earth's core

Illustration of Earth's interior.

(Dixon Rohr/ NASA/JPL-Caltech)

It was less than a decade ago when Xiaodong Song and fellow seismologist Paul Richards at Columbia University confirmed that the Earth's inner core, roughly 5,000 kilometres (3,100 miles) below the surface, can spin independently.

The researchers learnt about the inner core's rotation by tracking seismic wave readings from repeated earthquakes that travelled through the inner core — from the South Atlantic to Alaska between 1967 and 1995.

Subsequently, they found that the quakes all originated in the same region, but the travel time of seismic waves stemming from those earthquakes had changed. This indicated that the inner core's rotation was faster compared to the planet's mantle.

Now, in this new study, geophysicists have revisited the data from the 1960s to 1990s and compared it with more recent seismic patterns. Their observations show that Earth's inner core has paused its movements and may even be reversing the direction of its spin.

"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 in a multidecadal oscillation, with another turning point in the early 1970s," geophysicists Yi Yang and Xiaodong Song report in their paper.

The patterns suggest that inner core rotation paused sometime around 2009. Interestingly enough, this isn't the first time such an event has been recorded!

It turns out that Earth's inner core behaves like a swing, moving back and forth. One cycle of this swing lasts for almost seven decades, implying that every 35 years, the inner core undergoes rotation reversal. Such a phenomenon previously transpired around the 1970s, and the next change in direction may occur around the 2040s.

In fact, this seven-decade oscillation also seems to coincide with changes in the Earth's magnetic and gravitational fields, along with broader geophysical phenomena that impact the length of the day.

"These observations provide evidence for dynamic interactions between the Earth's layers, from the deepest interior to the surface," conclude Yang and Song, the co-authors of the study.

They have also hinted at "a resonance system across different Earth layers" - as if the planet's heart is thrumming to the same beat despite complex interactions and networks controlling a range of phenomena in this complex world.

This study was published in the journal Nature Geoscience and can be accessed here.

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