One of the most interesting discoveries about Earth in the past few decades concerns the Earth’s magnetic poles. Paleomagnetic records show that the poles have flipped places 183 times in the last 83 million years. That’s about every 450,000 years on average, though there were ten million years between flips in at least two cases.

The Earth’s magnetic field is experiencing some rapid changes right now, but scientists say that has no relation to pole flipping.

When the poles flip, scientists call it a geomagnetic reversal, and the last one happened about 780,000 years ago. It takes between 2,000 and 7,000 years for the poles to reverse. The evidence is contained in magnetic minerals inside rocks. Magnetic minerals record the strength and direction of Earth’s magnetic fields when they’re locked in place, either as sediments or in magma. The study of magnetism in Earth’s ancient rocks is called paleomagnetism.

Currently, there’s a region in the South Atlantic where the geomagnetic field is rapidly weakening. It’s called the South Atlantic Anomaly (SAA), and it’s led to questions about its role in geomagnetic reversal if any.

The South Atlantic Anomaly in 2020. Image Credit: Christopher C. Finlay, Clemens Kloss, Nils Olsen, Magnus D. Hammer, Lars Tøffner-Clausen, Alexander Grayver & Alexey Kuvshinov -
The South Atlantic Anomaly in 2020. Image Credit: Christopher C. Finlay, Clemens Kloss, Nils Olsen, Magnus D. Hammer, Lars Tøffner-Clausen, Alexander Grayver & Alexey Kuvshinov – “The CHAOS-7 geomagnetic field model and observed changes in the South Atlantic Anomaly”, Earth, Planets and Space, Volume 72, Article number 156 (2020), https://earth-planets-space.springeropen.com/articles/10.1186/s40623-020-01252-9, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=99760567

Scientists have known about the SAA for a while. What they didn’t know for sure was if the anomaly signifies an imminent geomagnetic reversal. Researchers behind a new study looked at evidence going back thousands of years to determine if the SAA is heralding an upcoming reversal.

In the past 180 years, the strength of Earth’s magnetic field has decreased by about 10 percent. During that same time, the size of the SAA has grown. Scientists have speculated that these events might be related to a geomagnetic reversal.

A new study in the Proceedings of the National Academy of Sciences searched for a link between the SAA, the decreasing field strength, and geomagnetic reversals. It’s titled “Recurrent ancient geomagnetic field anomalies shed light on future evolution of the South Atlantic Anomaly.” The lead author is Andreas Nilsson, a geologist at Lund University in Sweden.

“We have mapped changes in the Earth’s magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are probably recurring phenomena linked to corresponding variations in the strength of the Earth’s magnetic field,” Nilsson said in a press release.

Illustration of the invisible magnetic field lines generated by the Earth. Unlike a classic bar magnet, the matter governing Earth's magnetic field moves around. The flow of liquid iron in Earth's core creates electric currents, which in turn create the magnetic field. Credit and copyright: Peter Reid, University of Edinburgh.
Illustration of the invisible magnetic field lines generated by the Earth. Unlike a classic bar magnet, the matter
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