New findings reveal that Earth's inner core is changing shape, providing scientists with fresh insights into the planet’s deepest layer. Getty Images
Scientists who recently confirmed that Earth’s inner core had reversed its spin have now made another discovery—the shape of the inner core is changing.
The Earth’s core consists of a solid metal inner core surrounded by a liquid outer core. For years, researchers suspected that the inner core deformed over time as it rotated. Now, for the first time, evidence shows that its shape has actually changed in the past 20 years. These changes were detected using seismic waves from powerful earthquakes that reached the center of the Earth.
In a previous study, scientists found that the inner core used to spin faster than the rest of the planet. However, around 2010, its rotation slowed down and began moving in the opposite direction. Their latest research, published in Nature Geoscience, builds on this discovery by analyzing earthquake data from 1991 to 2023.
How Scientists Detected the Changes
Dr. John Vidale, one of the study’s lead authors, explained that comparing seismic signals over time allowed them to identify deformations in the core’s surface that could not be explained by rotation alone. These changes might provide insight into the powerful forces deep inside Earth that generate our planet’s protective magnetic field.
Dr. Yoshi Miyazaki, a planetary scientist not involved in the study, said that while previous research focused on changes in core rotation, this new study highlights how the core’s shape is shifting. He believes this discovery will spark further debate and research.
What’s Happening in the Inner Core?
The Earth’s inner core, made mostly of iron and nickel, is about 70% the size of the Moon. It experiences extreme conditions, with temperatures reaching 9,800°F (5,400°C) and pressures over 3 million times greater than Earth’s surface. Since it cannot be directly observed, scientists study it by analyzing how seismic waves travel through it.
Earthquakes produce two types of waves: P waves, which move in the direction of travel, and S waves, which move perpendicularly. Researchers focused on changes in a specific type of P wave (PKIKP waves) and found evidence of core deformation near the boundary where the solid inner core meets the liquid outer core.
Vidale described the findings as “almost science fiction,” as the core’s surface might be shifting like slow-moving landslides under extreme pressure.
How This Affects Earth’s Future
Scientists believe that as the solid inner core continues to spin, the molten outer core surrounding it will gradually shrink. Over billions of years, the inner core will absorb more of the liquid outer core until Earth’s core becomes a fully solid sphere. If this happens, Earth’s magnetic field will weaken, exposing the planet to harmful solar radiation. However, long before this can occur, Earth itself will likely be destroyed as the Sun expands into a red giant.
For now, scientists will continue studying the core to better understand its movements and what they mean for Earth’s long-term evolution.
