Earth’s inner core has stopped spinning and is about to change direction: Exploration

Planet Earth


Like clockwork, we wake up every morning, rummage through our stash to find something to eat, and prepare that perfect cup of coffee (or tea) to get us through the day. At first, the same routine day after day isn’t that boring, but once the clouds of monotony begin to cast their shadow, we start looking for a change. And thousands of kilometers below our feet, the inner core of the Earth agrees with this human tendency!

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

The study by scientists at Peking University in Beijing reveals that sometime in the last decade, the Earth’s inner core (which normally rotates faster than the mantle) stopped doing so! Instead, it appears to reverse the direction of its rotation.

Diving into the mysteries of the Earth’s core

Illustration of the Earth's interior.  (Dixon Rohr/NASA/JPL-Caltech)

Illustration of the Earth’s interior.

(Dixon Rohr/NASA/JPL-Caltech)

Less than a decade ago, Xiaodong Song and fellow seismologist Paul Richards of Columbia University confirmed that Earth’s inner core, roughly 5,000 kilometers (3,100 miles) below the surface, can rotate independently.

The researchers learned about the rotation of the inner core by tracking seismic wave readings from repeated earthquakes that passed through the inner core, from the South Atlantic to Alaska between 1967 and 1995.

They subsequently found that all the quakes had occurred in the same region, but the travel times of the seismic waves emanating from these earthquakes had changed. This indicates that the rotation of the inner core is faster compared to the mantle of the planet.

Now, in this new study, geophysicists have revisited data from the 1960s to the 1990s and compared it to more recent seismic models. Their observations show that the inner core of the Earth has stopped its movements and can even reverse the direction of its rotation.

“We show surprising observations that indicate that the inner core has almost stopped rotating in the last decade and may undergo a reversal in a multidecadal oscillation, with another tipping point in the early 1970s,” report geophysicists Yi Yang and Xiaodong Song in their paper.

The models suggest that the internal rotation of the core stopped sometime around 2009. Interestingly, this is not the first time such an event has been recorded!

It turns out that the inner core of the Earth behaves like a cradle, moving back and forth. One cycle of this oscillation lasts almost seven decades, meaning that every 35 years the inner core undergoes a rotation reversal. A similar phenomenon occurred before around 1970, and the next change in direction may occur around 2040.

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

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

They also hinted at a “resonant system in different layers of the Earth” – as if the heart of the planet beats with the same rhythm despite the complex interactions and networks controlling a number of phenomena in this complex world.

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


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