They find that the core of the Earth oscillates under our feet and changes direction every 6 years

A team of American scientists has found evidence that the inner core of the earth sways, a finding that contradicts previously accepted models that suggested it rotated systematically and faster than the planet’s surface.

The study, led by University of Southern California (USC) and released this Friday in “Scientific advances”, shows that seismic data show that the inner core changed direction between 1969 and 1974. Scientists say their inner core motion pattern also explains the change in day length, which in recent decades has been shown to fluctuate persistently.

“From our results, we can see that the surface of the Earth is shifting relative to its inner core,” he says. John E Vidaleco-author of the study and professor at USC.

“Our latest observations show that the inner core it rotated slightly slower between 1969 and 1971 and then it moved in the other direction between 1971 and 1974. We also observed that the length of the day increased and decreased, as expected. “

Though it is impossible to observe directlyin the last thirty years, knowledge of the inner core has enormously expanded, again thanks to indirect measurements. During this time, it has been shown that the core –a hot, dense iron ball Solid of plutonic dimensions: it moves and changes.

In 1996, research was the first to propose that the inner core rotates faster than the rest of the planet – what is known as super rotation-, about 1 degree per year.

A subsequent study by Vidale and Wei Wang, based on data from the Large Aperture Seismic Array (LASA), a U.S. Air Force facility in Montana, confirmed that the inner core was spinning slower than expected, about 0.1 degrees per cent. year. The study was based on the waves generated by the Soviet underground nuclear bomb test made between 1971 and 1974 in the arctic archipelago of Novaya Zemlya, thanks to a new technique.

Applying the same methodology to a couple of previous atomic tests on the island of Amchitka, Alaska (Milrow in 1969 and Cannikin in 1971), the authors found that the inner core had reversed direction, subgerminating by at least a tenth of a degree per year.

It was the first time that the well-known six-year swing was confirmed by a direct seismological observation“The idea that the inner core wobbles existed, but the community was divided over its feasibility,” says Vidale. “We studied it expecting to see the same direction and speed of rotation in the previous atomic test pair, but instead we saw the opposite. We were quite surprised to see it move in the opposite direction“, She said

Vidale and Wang believe future investigations will hinge on the discovery sufficiently accurate observations comparing them to these results, which should be difficult, given that the era of underground atomic testing in the United States is over.

On the other hand, the study supports the hypothesis that the inner core oscillates according to variations in the length of the day – plus or minus 0.2 seconds in six years – and geomagnetic fields, which coincide with the theory in both amplitude and phase. “The inner core is not fixed: moves under our feetand it seems to come and go for a couple of miles every six years, ”says Vidale.

Now is the time to find out whether the inner core is progressively moving or whether it’s mostly locked away from everything else in the long run, the authors explain. EFE