Scientists have discovered changes in the shape of Earth's inner core, a hot, solid metal ball surrounded by a liquid metal outer core. This finding builds upon a 2024 study confirming the inner core's spin reversal around 2010. The research, published in *Nature Geoscience*, utilizes earthquake data from 1991 to 2023. The team analyzed variations in the height of seismic waves (PKIKP waves), indicators of changes to the inner core's surface.
Dr. John Vidale (Dean's Professor of Earth Sciences at the University of Southern California's Dornsife College of Letters, Arts and Sciences) noted that comparing signals when the inner core returns to the same position reveals differences not explained by rotation.
The inner core, approximately 759 miles (1,221 kilometers) in radius, experiences temperatures up to 9,800 degrees Fahrenheit (5,400 degrees Celsius) and pressures reaching 365 gigapascals (GPa). Researchers analyzed 168 paired waves from earthquakes near the South Sandwich Islands to detect shape changes.
The study suggests the boundary where the solid inner core meets the liquid outer core may be more malleable. While the exact deformation is uncertain, it may involve the outer core pushing and moving the inner core. The interaction between the spinning inner core and churning outer core generates magnetic energy, protecting Earth from solar weather and radiation. The inner core is slowly siphoning molten metal from the outer core, a process expected to continue for billions of years.