Scientists say Earth’s inner core is changing shape

Scientists who just months ago confirmed that Earth’s inner core has recently changed its rotation have made a new discovery about one of our planet’s deepest mysteries – they have discovered changes in the shape of the inner core. The Earth’s inner layer is a hot, solid metal ball surrounded by a liquid metal outer core. For decades, planetary scientists have suspected that the solid inner core has deformed over time as it rotates, reported by CNN.

Now, researchers have found the first evidence of changes in the shape of the inner core over the past 20 years. Signs of the core’s deformation appeared in waves from earthquakes strong enough to reach the center of the Earth. The research team used the same earthquake data for a 2024 study to settle a long-standing debate about the rotation of the inner core. They found that the inner core once rotated faster than the Earth itself. But since about 2010, the rotation of the solid inner core has slowed. It is now spinning backwards, relative to the rest of the planet.

Forces deep inside Earth

Their new study builds on that discovery, using earthquake data collected from 1991 to 2023. The scientists’ previous work on core rotation helped them interpret variations in the height of seismic waves, identifying them as indicators of changes on the surface of the inner core. We can compare the signals we see when the inner core returns to the same position it was in at another time and see if there are differences that cannot be explained by rotation.

The changes in shape in the core may hold clues about the forces deep inside Earth that power our magnetosphere, the invisible lines of magnetic energy that protect our planet from solar weather and deadly radiation, the researchers report. The Earth evolves on a geological timescale, so observing changes on an annual timescale is always intriguing, as it improves our understanding of the dynamics of the inner core.

The inner core is the most remote and mysterious

Previous studies have already discussed how the inner core’s rotation has changed over the past decade, and this study introduces a new perspective—non-rotational changes—adding another dimension to the discussion. I think it will fuel this debate even more. Of all the layers of the Earth, the inner core is the most remote and mysterious. It’s a place so different from our everyday lives, with different time frames, different materials, and incredible forces. And yet, we can go there and learn more about it just by looking at some of the latest observations.

Scientists analyzed 168 paired waves from earthquakes at 42 locations near the South Sandwich Islands, a chain of volcanic islands in the South Atlantic Ocean. Tracking the speed and direction of the core’s rotation allowed the researchers to detect changes in the shape of the core. Perhaps the terrain is changing up and down. Perhaps it’s sliding, like landslides. The most likely scenario is that the outer core is simply pushing on the inner core and moving it a little. Although only one location in the inner core showed signs of deformation between 2004 and 2008