Earth’s inner core may change its rotation

Why is it important: There are many mysteries around the Earth’s core. One is related to seismic fluctuations over the past few decades. Some scientists believe that this is evidence of changes in the rotation of the inner core, but others disagree about their timing. The effects for us on the surface were probably minimal.

New research offers that the inner core of the Earth has recently stopped rotating and is changing its direction. The changing rotation may be due to small fluctuations in the length of the day from year to year.

In the January 2023 issue of Nature Geoscience, researchers Xiaodong Song and Yi Yang from Peking University of China argued The planet’s inner core stopped rotating relative to other layers around 2009. The Earth’s inner core, located later, about 3100 miles below our feet, made of hot iron and about the size of Pluto, can rotate independently of the mantle and crust due to the liquid outer layer. core that surrounds it.

The researchers said that the inner core began to change its rotation after stopping, and that this process repeats itself approximately every 35 years. The last reversal occurred in the early 1970s; the next one could be in the mid-2040s.

The study involved measuring seismic waves that travel through the Earth. These ripples date back to 1964 and result from earthquakes and nuclear explosions. Waves showing significant temporal changes in the early 1990s have shown relatively little change over the past decade, possibly indicating that the core’s rotation has stopped. The researchers found similar data from the early 1970s, and the data correlated with changes in day length.

John Vidale, a seismologist at the University of Southern California, disagrees. He believes that the inner core fluctuates every six years based on nuclear explosion data from the late 1960s to the early 1970s. Other geophysicists have many theories, but Vidale doesn’t believe any one model adequately explains all the data.

One theory claims that the inner core shifted significantly between 2001 and 2013, but has not moved since. Australian National University geophysicist Hrvoe Tkalcic stated in his study that the core cycles back and forth every 20 to 30 years rather than changing in the same direction every 35 years.

However, he also doubts the correctness of all the proposed theories. Seismic data provide only limited information about what is happening inside the Earth. Other theories postulate that the inner core may have another core within it. So scientists have yet to come to a consensus about what is happening inside the Earth.