A new study has found evidence that the outer boundary of Earth’s solid inner core is shape-shifting, challenging our understanding of the planet’s deepest interior region. Researchers detected changes in the seismic signals generated by earthquakes that pass through the Earth, suggesting that the inner core is not perfectly solid.
The inner core, a ball of iron and nickel about 1,500 miles wide, has been thought to be stationary at its center. However, geophysicists have previously reported variations in its rotation rate, with some periods showing faster spinning than others. The new study, published in Nature Geoscience, uses seismic data from earthquakes in the South Sandwich Islands to analyze the shape-shifting phenomenon.
Lead researcher John Vidale explains that the outer core is likely “tugging on” the inner core, causing it to move slightly. This movement could be due to turbulent flow in the outer core or gravitational pull from denser parts of the mantle. The study’s findings reconcile a long-standing debate over whether differences in seismic signals are caused by changes in rotation rate or shape.
While the researchers are confident in their results, acknowledging that the finding is not “bulletproof,” they emphasize the need for further data collection to fully understand this phenomenon. Experts agree that more research is required to resolve the question of shape-shifting in Earth’s inner core.
Source: https://www.nytimes.com/2025/02/10/science/inner-core-earth-shape-change.html