A recent study monitors a slowdown in the rotation of the Earth’s inner core | Sciences

A recent study monitors a slowdown in the rotation of the Earth’s inner core |  Sciences

The Earth’s inner layers and how they rotate and interact affect some geophysical observations at the surface, including changes in the length of the day and the Earth’s magnetic field. Can scientists monitor its rotation rate?


In the mid-nineties of the last century, scientists found evidence that the inner core of the Earth – that iron ball that is very hot and slightly smaller in size than the moon – rotates at a special rate, slightly faster than the rotation of the planet Earth.

However, a recent study published in Nature Geoscience on January 23 reported that the rate of rotation of the Earth’s inner core has slowed since 2009 until it coincided with the surface’s rotation for some time, and is now lagging behind in the rate of rotation of the surface. .

Earth’s inner and outer core

About 3,000 miles (4,828 km) below Earth’s surface, a hot ball of solid iron (the inner core) floats inside a liquid outer core (the outer core).

According to the press release published by Nature Asia, the liquid outer core separates the inner core from the rest of the Earth, enabling the inner core to rotate differently from the rotation of the Earth itself.

Earth’s inner core influences some fundamental aspects of our planet, including the length of the day and fluctuations in the Earth’s magnetic field.

Geologists also believe that the energy emitted from the inner core causes the liquid in the outer core to move, generating electric currents that in turn cause a magnetic field that surrounds the planet and protects living organisms on the surface from the most harmful cosmic radiation.

Earthquakes generate strong waves that can penetrate the Earth’s inner core (Pixaby)

Seismic waves offer the solution

The magnetic field generated in the outer core affects the rotation of the inner core, but the speed and pace of rotation of the Earth’s inner core has been the subject of scientific discussion for years.

According to the research summary published in the journal “Nature Geoscience”, earthquakes can generate waves strong enough to penetrate the inner core, and thus can provide valuable information about the structure of the inner core, as an extension of the length of the paths that these seismic waves can travel to.

So scientists at Peking University analyzed variations of seismic waves that have passed through Earth’s inner core since the 1960s.

Scientists discovered that seismic wave trajectories have shown little change since 2009, in contrast to what they showed in past years, which indicate large temporal discrepancies, which indicates that the rotation of the inner core may have stopped temporarily since 2009.

Scientists have identified a 6-year cycle of super and sub-rotation of the Earth's core (Edward Sotelo - University of Southern California
The rate of rotation of the Earth’s inner core has slowed since 2009 until it coincides with the rotation of the surface (websites)

Reflection in the direction of rotation

However, this slowdown was not the first of its kind in the modern era. Indeed, the Earth’s inner core experienced a similar slowdown in the early 1970s.

Scientists believe that this latest slowdown in the inner core is related to a spin reversal, as the solid iron ball slides in the opposite direction as part of a 7-decade-long oscillation.

They also concluded that this fluctuation in the rotation of the Earth’s inner core – in conjunction with the cyclical changes in the Earth’s surface system – can explain the interactions between the different layers of the Earth.

The authors suggest that this difference is related to changes in geophysical observations on the Earth’s surface, such as the magnetic field and the length of the day.


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