Earth's inner core is 'deforming' discovered

Scientists have made a surprising new discovery: The Earth's inner core - a solid mass of metal deep below the liquid outer core - is not only changing its rotation speed, but may also be deforming.

John Vidale, a geophysicist at the University of Southern California in Los Angeles, announced the discovery at the American Geophysical Union conference on December 9. The discovery could resolve a long-standing debate about changes taking place at the center of the Earth.

The Earth's core is not only changing its rotation speed, but may also be deforming. (Illustration).

Because scientists cannot directly probe the Earth's core, they have to rely on studying seismic waves from earthquakes. They often monitor earthquakes in the South Sandwich Islands near Antarctica, which are across the street from the measuring stations in Alaska. Seismic waves travel through the Earth like sound waves through water, with some passing through the inner core before reaching Alaska.

In the new study, Vidale's team analyzed about 200 pairs of earthquakes that occurred between 1991 and 2024. They found subtle differences in wave patterns recorded in Yellowknife, Canada, that were not present in Fairbanks, Alaska, suggesting that the inner core surface is deforming.

Scientists have proposed a number of hypotheses. It could be that the entire inner core is deforming, like a rugby ball changing shape. Or it could be that only certain areas on the surface are swelling or contracting, forming 'dents' and 'bulges.' These changes could be due to the gravitational pull of the tectonics — the largest layer inside the Earth — or to the movement of material in the outer core.

Xiaodong Song, a geophysicist at Peking University who was one of the first to detect differences in the rotation of the inner core compared to the rest of the Earth, agreed with Vidale's findings. While the difference in wave patterns is mainly due to changes in rotation, other processes such as surface changes could also be at play . "It's not one or the other ," he said.

Although scientists have yet to determine how these changes will affect life on Earth's surface, they are continuing to study the phenomenon to better understand it, Mr. Vidale concluded.