by H. Richter, Feb 10, 2025 in Science
Seismic waves radiating through the planet’s interior point to dramatic activity
More than 5000 kilometers beneath our feet, Earth’s iron inner core seems to be spinning, growing, and occasionally speeding up or slowing down. It’s also likely changing shape, according to research published today in Nature Geoscience, with some areas rising and falling up to 1 kilometer within a few years. Although most changes are likely subtle bumps in the iron landscape, some could mirror rising mountains and tumbling landslides. Though these movements—picked up as seismic waves traveling through the planet—have scant effect on us surface dwellers, they help bring into focus a more dynamic picture of Earth’s insides.
Severine Rosat, a geophysicist at CNRS, the French national research agency, who was not involved in the work, says she’s “surprised” the team was able to detect such subtle and fleeting changes in Earth’s core. “That’s quite encouraging for other seismologists.”
The inner core is a roughly 5200ºC, 2500-kilometer-long ball of mostly solid iron that helps power Earth’s magnetic field. Because no instruments can penetrate even remotely close to the depths needed to study the core, scientists instead take advantage of natural events that rocket straight through it: seismic waves from earthquakes. When these waves travel through Earth, they can either pass through the inner core or get deflected at its surface, logging their paths as wavy lines that detectors record on the opposite side of the planet. When two earthquakes occur in the same location at different times in history, scientists can compare their paths to see what has changed at the center of Earth.
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