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Earth's inner core may be reversing rotation, study suggests

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Deep below our feet Earth's dense core may have stopped spinning – and could even be shifting its rotation – a ground-breaking study has suggested.

The paper, published in Nature Geoscience, analysed how seismic waves from earthquakes passed through the core from the 1960s, concluding rotation may have paused since 2009 as little change has been observed since then.

Scientists have long known that the inner core rotates, but the speed of that rotation and whether it varies has long been debated. This latest study sheds more light on the process.

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The research ultimately suggests the core could be oscillating according to a 70-year cycle, with the previous turning point occurring in the early 1970s.

Prior to this it was believed to be oscillating on a six-year cycle.

"We infer the inner core rotation changes direction every 35 years – with a period of about 70 years, but we have not observed the full cycle for the lack of seismic data," one of the lead scientists, Xiaodong Song, told 9news.com.au.

"The phenomenon does not affect our day-to-day lives, but helps us understand how the inside of the Earth works and may have an impact on the other parts of the Earth, such as geomagnetic field, earth rotation, surface processes in the longer term."

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The findings are supported by changes in geophysical observations on the surface, such as the magnetic field and the length of day.

The inner core was first discovered in 1936, by researchers studying how seismic waves travelled through the planet.

It's believed to be about 7,000 kilometres wide, comprises a solid centre made mostly of iron.

This sits inside a liquid outer shell comprised of molten iron and other elements.

Both cores help maintain Earth's magnetic field, so knowing how they work and interact is important.

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