The reversal of the Earth’s inner core is in a cycle that can last about 70 years. This could affect Earth’s day length and its magnetic field Science News.
“We saw clear evidence that the inner core was spinning faster than the surface, but around 2009 it almost stopped,” said geophysicist Xiaodong Song of Peking University in China. Now it is slowly moving in the opposite direction.”
Such a profound change may sound strange, but the Earth is often unstable.
Drilling through the ever-changing crust leads to the giant mantle, where huge chunks of rock have flowed viscously over millions of years, sometimes emerging to erode the upper mantle.
Going deeper will reach Earth’s liquid outer core. Here, circulating streams of molten metal evoke the Earth’s magnetic field. And at the center of that melt is a solid, spinning ball of metal about 70 percent larger than the Moon.
Studies have suggested that this solid heart can rotate inside the liquid outer core and be forced by the magnetic torque of the outer core.
The researchers also argue that the mantle’s immense gravity could exert an erratic braking force on the rotation of the inner core, causing it to oscillate.
Evidence for the oscillating rotation of the inner core first appeared in 1996. Geophysicist Paul Richards of Columbia University’s Lamont-Doherty Earth Observatory, USA reports: over a period of 3 decades For centuries, seismic waves from earthquakes take varying amounts of time to pass through the solid heart of the Earth.
The researchers suggest that the inner core rotates at a different speed than the mantle and the crust, causing the difference in timing. The Earth rotates about 360⁰ in a day. Based on their calculations, the researchers estimate that the inner core rotates on average about 1⁰ per year faster than the rest of the Earth.
However, these findings are also controversial in the global research community.