A study published in the scientific journal Nature Geoscience, indicates that the inner core's deformation is occurring at the boundary where it meets the liquid outer core, which hovers right at its melting point.
"What we're observing in the study for the first time is likely the outer core disturbing the inner core," Professor John Vidale, who led the research, said, according to BBC News. He added that the inner core's edges may have been deformed.
The researchers analyzed seismic waves generated by earthquakes. "We can compare the signals that we see when the inner core is returned to the same position as it was in some other time and see if there's differences that can't be explained by the rotation," Vidale explained, as reported by AccuWeather.
The team examined patterns of seismic waves from 121 repeating earthquakes recorded near Antarctica's South Sandwich Islands and off the coast of South America between 1991 and 2024. They focused on wave patterns from earthquake pairs recorded decades apart, which revealed subtle but undeniable differences suggesting the inner core's structure is evolving over time, according to Popular Science.
The Earth's inner core is a scorching-hot, solid mass of iron and nickel, measuring roughly 2,440 kilometers (1,516 miles) across and located about 5,150 kilometers below the surface. It is surrounded by a liquid outer core, and together, these layers are responsible for generating Earth's magnetic field.
Understanding the inner core's behavior is crucial, as it may influence how the planet's protective magnetic shield behaves over time. "The magnetic field has shown 'jolts' at various times in recent decades, and we would like to know if this is related to what we are observing at the boundary of the inner core," Vidale noted, as per BBC News.
Previously, scientists believed that the inner core rotated independently of the outer liquid core and the rest of the planet, at times spinning slightly faster than the Earth's surface. Recent studies, however, indicated that the rotation of the inner core changes speed over time and may even reverse direction relative to the rest of the Earth.
By analyzing seismic records from 121 earthquakes originating near the South Sandwich Islands between 1991 and 2024, researchers were able to track how the inner core's rotation speeds up and slows down over time. This suggests that the inner core not only changes speed but also shape, particularly at the boundary where it is near the melting point.
"Previous studies have already discussed how inner core rotation has changed over the past decade, and the study introduces a new perspective—non-rotational changes—adding another dimension to the discussion," said Dr. Yoshi Miyazaki, an associate professor at Rutgers University.
The inner core's deformation indicates that it is more malleable than previously thought, especially at the boundary where it meets the liquid outer core. This area hovers right at its melting point and may be deformed by up to 100 meters or more in some regions, with surface deformations estimated to range from hundreds of meters to several kilometers wide, as reported by BBC News.
The article was written with the assistance of a news analysis system.