The river of molten iron flowing 1,400 miles below the Pacific Ocean in Earth’s outer core has surprised scientists by changing direction.
The observation provides new insights into the behaviour of the liquid outer core, which plays a key role in generating Earth’s magnetic field. Without this magnetic shield, the planet would be dangerously exposed to solar radiation.
Researchers at the University of Edinburgh checked ground observations and satellite data between 1997 and 2025. They report in The Journal of Studies of Earth’s Deep Interior, that in 2010, a broad region of iron-rich fluid beneath the equatorial Pacific switched from moving weakly westwards to strongly eastwards.
Lead author of the study, Frederik Dahl Madsen, at the University’s School of Geosciences, said: “The large-scale flow reversal beneath the Pacific raises new questions about the behaviour of Earth’s deep interior.
"Scientists now want to understand whether the reversal represents a short-lived fluctuation, part of a repeating oscillation, or a new stable equilibrium for core circulation.”
According to Elisabetta Iorfida, the Interior and Exterior Fields Earth Scientist at the European Space Agency, the Pacific reversal challenges assumptions that the outer core is dominated by stable westward circulation.
“This study shows that regional changes can emerge rapidly within just a decade,” she said. “The findings may also help scientists investigate possible interactions between Earth’s outer core, inner core and lower mantle and, therefore, give more insights into core-mantle boundary, which is a critical region for the deep-Earth dynamics.”
The ESA’s latest data suggest the eastward flow may now be weakening again after reaching a peak several years ago, raising the possibility that the event represents a temporary oscillation or part of a longer natural cycle in core dynamics.
These changes occur far below Earth’s surface and pose no immediate danger to people or climate. But scientists think they are fundamental to understanding how our planet works, and how the outer core generates Earth’s protective magnetic field.
The magnetic field is not fixed. It slowly changes over time as the core flow evolves, affecting everything from navigation systems to spacecraft operations and models of near-Earth space weather.
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