One “fun fact” that emerges from geology is that the magnetic north pole hasn’t always been near the geographic North Pole—it also keeps a home near the geographic South Pole, which it occupies when the orientation of Earth's magnetic field flips. Although magnetic flips appear more or less randomly distributed through time, it’s tempting to think we’re overdue for a flip, given how long it has been since the last one (about 780,000 years). Add in observations showing that the north pole has been wandering pretty rapidly as of late and that the overall strength of the field has been declining, and you might even get your hopes up.
The weakening of the field has been mainly down to action in the Southern Hemisphere. There’s a long-lived region of lower field intensity stretching from southern Africa to South America that has been getting even weaker. Models of the Earth’s magnetic field are a little fuzzy there because we don’t have many records of past behavior from that area. That makes it hard to know what to make of its current behavior.
John Tarduno of the University of Rochester and the University of KwaZulu-Natal led a team of researchers looking to fill in some of the historical gaps by building a record from southern Africa. They relied not on a geologic record, but on unintentional archives left behind by human communities. Centuries ago, the villages of people who farmed the area responded to droughts with ritual burnings of huts, grain bins, and animal enclosures. As the structures burned, the intense heat would essentially fire the clay floors like ceramic pottery (and in the case of the animal enclosures, bubbly glass). While still hot, magnetic minerals could align with the Earth’s magnetic field, only to be frozen in place as the material solidified. So each burned structure created a magnetic snapshot.
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