A study by researchers from UC Berkeley, Columbia University, Italy and France shows that the most recent reversal of Earth’s magnetic field occurred in fewer than 100 years, which is much more rapidly than previously believed.
A magnetic field reversal is when the Earth’s magnetic poles are switched – a phenomenon that has occurred many times in history. Magnetic fields usually remain at a certain intensity but weaken significantly before reversing.
Previously, researchers believed reversals occurred over thousands of years. The discovery that reversals can happen in such a short time is significant because it can help scientists further understand how magnetic reversals behave.
In the most recent magnetic reversal, the Earth’s field reversed a few times over several thousand years before it finally “snapped,” making its final reversal into its current orientation in fewer than 100 years, Renne said.
Researchers don’t have clear-enough records of other reversals to know whether this behavior is normal, he added.
Bruce Buffett, campus earth and planetary sciences chair and professor, unaffiliated with the project, questioned the study’s definition of a reversal, arguing that a complete magnetic reversal takes much longer.
According to Buffett, it’s true that the field can switch direction within 100 years, but when that rapid switch occurs, the field is still relatively weak. It actually takes thousands of years for the field to regain its normal intensity in its reversed direction, he said.
“I can tell you that a reversal can’t (take) place in a 100 years, but something that goes from very weak to very weak in another direction can take place in that amount of time,” Buffett said.
Yet the study was “remarkable” for obtaining such a detailed and accurate record, he said.
Moving forward, the researchers will continue the study and further analyze sediment samples.
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