Scientists baffled as Earth tipped on its side and back again in bizarre ‘cosmic yo-yo’

NASA scientists explore the ‘anomaly’ in Earth’s magnetic field

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The event, which is officially and somewhat controversially known as the true polar wander (TPW), occurs when a planet’s outer layers shift around the core. In this particular case, the Earth’s crust appears to have tilted by about 12 degrees relative to the planet’s axis. Until recently, there was some evidence to suggest the planet experienced a TPW between 145 million and 66 million years ago – the Cretaceous period.

But this theory was hotly debated among the scientific community and, according to researchers at the Tokyo Institute of Technology (Tokyo Tech), the evidence “has been contentious” at best.

But a new study published in the journal Nature Communications may have finally solved the mystery after exposing the “most convincing evidence to date” of a TPW some 84 million years ago.

The groundbreaking study was led by the Earth-Life Science Institute (ELSI) at Tokyo Tech, with researchers from the California Institute of Technology (Caltech) and the Institute of Geology and Geophysics in Beijing.

According to the new research, the TPW occurred some 84 million years ago during the Late Cretaceous with evidence of this phenomenon found in limestone deposits in Italy.

The researchers studied the movements of prehistoric Earth’s crust by analysing magnetic minerals trapped in fossilised bacteria.

Sarah Slotznick, study co-author and geobiologist at Dartmouth College, said “these Italian sedimentary rocks turn out to be very special and very reliable because the magnetic minerals are actually fossils of bacteria that formed chains of the mineral magnetite.”

Trapped inside the fossils, tiny crystals of the mineral line up with the planet’s magnetic field like a compass.

This allowed the researchers to map the planet’s ancient magnetic field to determine where the planet’s spin axis wandered in relation to its crust.

Earth's magnetic field to 'switch' in natural phenomena

Principle Investigator Joe Kirschvink explained: “Imagine looking at Earth from space.

“True polar wander would look like the Earth tipping on its side, and what’s actually happening is that the whole rocky shell of the planet—the solid mantle and crust—is rotating around the liquid outer core.”

In essence, the Earth is comprised of multiple rocky layers surrounding a solid inner core, a liquid metal outer core and a solid mantle.

Because the outer core is liquid, the solid mantle and crust have the freedom to slide around on top of it.

Individual parts of the crust, like tectonic plates, are continuously sliding around and moving on top or under one another.

During the TPW, however, all of these layers moved together in unison, giving the Earth a distinct, tilted look.

Because the laters all moved at the same time, scientists would not expect to see any major seismic activity during this period.

The planet’s magnetic field would have also been static during the TPW because it is generated by the inner core, which stayed in its place.

So instead of the Earth’s magnetic poles shifting – a phenomenon that is happening right now – it was the geographic poles that were tilted back and again.

According to the new study, the planet’s crust moved by a total of nearly 25 degrees over a period of five million years.

Tokyo Tech said in a statement: “The team also found that Earth appears to have corrected itself—after tipping on its side, Earth reversed course and rotated right back, for a total excursion of nearly 25 degrees of arc in about five million years.

“Certainly, this was a cosmic ‘yo-yo’.”

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