The power of subterranean pressure is reshaping the Earth’s inner core.

The inner core of Earth’s solids appears to have changed shape over the last 20 years or so, according to seismic wave measurements, but the behavior of these waves can also be explained by other shifts at the center of the planet.

Since the 1990s, models and earthquake measurements have shown that the inner core of Earth’s iron nickel moves at its own pace. Over decades, the inner core rotation is faster, slower than other planets, affecting the length of the day and more.

These rotational changes are primarily due to magnetic forces produced by convection in the Earth’s liquid outer core, they say. John Vidale At the University of Southern California. “That flow constantly torques the inner core.”

These magnetic forces, or related processes, can change the shape of the inner core and its rotation. In fact, previous measurements of seismic waves passing through the center of the planet seem to show just that. However, uncertainty regarding the rotation of the core made it impossible to distinguish between rotational changes and shape changes.

Now, Vidale and his colleagues are analyzing seismic waves generated by 128 earthquakes off the coast of South America between 1991 and 2023. All waves were measured by Alaskan instruments after passing through the planet.

From these, researchers have identified 168 sets of seismic waves that have passed through or near the same area of ​​the inner core, but have been away for years. It was only possible to identify these matches Recent work Vidale says it will better constrain the variation in rotation of the inner core.

Both waves of each pair that did not pass through the inner core shared a similar pattern, suggesting that in the region within the planet nothing had changed between the first and second earthquakes. Masu. However, the waves of the pair crossed with the inner core did not match.

Researchers say this suggests that the inner core not only slows down and speeds up rotation for decades but also changes shape. They say that these changes are magnetically pulled at the less viscous edge of the inner core of the solid or interaction between the inner core and the structure of the planetary core and the lower mantle. They say it is likely caused by interactions between the layers. The crust.

hrvojetkalčić At Australian National University, which was not involved in the study, this is a “step” to resolve changes in the internal core beyond rotation. However, he says that the shape change is not the only explanation for the seismic waves of incongruity.

As Vidale and his colleagues acknowledge, these differences can also be caused by unrelated changes in the outer core, convection within the inner core itself, or by eruption of melted material from the inner core. There is. “It’s really hard to tell,” Bidal says. He suggests that studying more repeated earthquakes in the future will help identify changes in more detail.

Tkalčić says seismological measurements in remote areas such as the seabed are also useful. “This is important for understanding the deepest inner evolution of Earth, from the time of the planetary layers to the present,” he says.