Earth's core has changed shape over past 20 years, study finds

The world is still going round in circles, but its heart is changing. A study published this Monday, February 10 in the scientific journal Nature Geoscience looks at a possible deformation of the Earth's core, a hot, solid metal ball surrounded by an outer core of liquid metal.

The 20 or so researchers found the first evidence of changes in the shape of the inner core over the past 20 years. The signs of the core's deformation were detected using waves from earthquakes powerful enough to reach the center of the Earth, data collected between 1991 and 2023.

Although it is impossible to observe the core directly, scientists study it by analyzing changes in the size and shape of seismic waves passing through it, which then allows the shape of the core to be calculated.

"We can compare the signals we see when the inner core returns to the same position as at another time and see if there are differences that can't be explained by rotation," a researcher from the University of Southern California told CNN .

Of all the layers of the Earth, the inner core is the most distant and mysterious. This solid sphere composed of iron and nickel is equivalent to 70% of the size of the moon, with a radius of about 1,221 kilometers.

"Visualizing what is happening on the surface of the inner core is almost science fiction," commented the Californian researcher. Many mysteries remain, especially because it is currently impossible for us to study this area directly other than through this indirect means.

Understanding how the Earth's core works is, however, essential to understanding the magnetic field that protects the planet and whether it could weaken or stop. The authors stress, however, that this new information is not a source of concern, and that at this stage it is only observations.

Overall, "it is very likely that this discovery will not affect our daily lives in one iota, but we really want to understand what is happening in the middle of the Earth," adds the researcher also quoted by the BBC .