Making heads spin: Scientists say Earth’s inner core has changed its rotation

According to a new study, the core of the Earth might have ceased rotating or could potentially be rotating in reverse.

The core of our planet is made up of an inner solid metal core, which accounts for approximately 70 percent of the moon’s size, and an outer layer consisting of liquid metal.

The general consensus is that the core rotates in a counterclockwise manner when viewed from the North Pole, just like the rest of the Earth.

Conversely, the rotation of the core came to a halt around 2009 and subsequently resumed, according to a study conducted by researchers at Peking University in China, which analyzed seismic wave data spanning the last six decades.

“We believe that like a pendulum, the Earth’s core is rotating in the opposite direction and then swinging back towards the surface, according to the study authors, Xiaodong Song and Yi Yang.”

They added that a full rotation (in one direction and then the opposite) of this swing takes approximately 70 years.

According to the researchers, the final shift in rotation before 2009 would have happened in the early 1970s, and the subsequent one is expected to occur in the mid-2040s.

Debatable discoveries

There is still considerable discussion regarding the composition of the Earth’s core, as acquiring data about it is exceedingly challenging.

Composed of fluid iron and nickel, it is believed that this outer core intersects with the Earth’s mantle at a depth of approximately 2,890 km, marking the boundary of the outer core.

The atoms of the metal are compacted, exerting intense pressure as a result of the solid iron and nickel, forming the inner core which begins approximately 5,000 km beneath the planet’s surface.

According to the examination of seismic waves triggered by earthquakes, it is thought to have been spinning in the identical direction as the remaining part of Earth, and it resides inside the fluid outer core.

Yang Yi and Song Xiaodong studied these seismic waves as a “gradual turning-back” associated with approximately seventy years as a part of the inner core in their published paper in Geoscience Nature.

John Vidale, a seismologist at the University of Southern California who was not part of the research, expressed, “This study is exceptionally careful and conducted by exceptional scientists who utilized a substantial amount of data.”

However, he included that “none of the current models truly clarifies all the accessible information adequately”.

A study published by Vidale last year suggests that the inner core of the Earth oscillates much more rapidly, with direction changing approximately every six years, based on seismic data from two nuclear explosions dating back to the late 1960s and 1970s.

Hrvoje Tkalcic, another geophysicist at the Australian National University, believes that the inner core’s cycle lasts for approximately 20 to 30 years, rather than the proposed 70 years in the study week’s nature of geoscience.

The researchers from Peking University claim in their paper that this oscillation is associated with changes in the length of days and changes in the Earth’s magnetic field, as observed in several other geophysical observations.

“These observations provide evidence for dynamic interactions between the deepest interior layers of Earth, potentially due to the exchange of angular momentum and gravitational coupling, surfacing from the mantle and core.”

“We hope that our research motivates researchers to design and test models treating the Earth as an integrated dynamic system,” they explain.