Earth’s magnetic field seems steady and true — reliable enough to navigate by.
Yet, largely hidden from daily life, the field drifts, waxes and wanes. The magnetic North Pole is currently careening toward Siberia, which recently forced the Global Positioning System that underlies modern navigation to update its software sooner than expected to account for the shift.
And every several hundred thousand years or so, the magnetic field dramatically shifts and reverses its polarity: Magnetic north shifts to the geographic South Pole and, eventually, back again. This reversal has happened countless times over the Earth’s history, but scientists have only a limited understanding of why the field reverses and how it happens.
New work from University of Wisconsin–Madison geologist Brad Singer and his colleagues finds that the most recent field reversal, some 770,000 years ago, took at least 22,000 years to complete. That’s several times longer than previously thought, and the results further call into question controversial findings that some reversals could occur within a human lifetime.
Read more at University of Wisconsin-Madison
Image: Study co-author Rob Coe and Trevor Duarte orienting cores from a lava flow site recording the Matuyama-Brunhes magnetic polarity reversal in Haleakala National Park, Hawaii, in 2015. (Credit: Brad Singer)