ExtremeTech reported a year ago on the anticipated flip of Earth’s magnetic field:
But the Earth’s magnetic field is shifting. New satellite data from the ESA shows that the Earth’s magnetic field is weakening 10 times faster than we previously thought — an indicator that scientists believe is a precursor to a geomagnetic reversal. At the time, there was nothing to worry about — previous geological records suggested that a geomagnetic reversal occurs over thousands of years. Now, however, a new study has analyzed rocks from the previous flip — the Matuyama-Brunhes magnetic reversal of 786,000 years ago — and found that the process completed in under 100 years. [doi: 10.1093/gji/ggu287]
Now archaeology has data to contribute. Samir S. Patel in Archaeology Magazine (Sept/October, 2015) reports on a byproduct of the research:
During the Iron Age, people [in southern Africa] would, perhaps because of a bad harvest, ritually “cleanse” their villages by burning them down. The fires burned hot enough to melt magnetic materials in the clay. When those materials cooled and solidified, they were remagnetized by the magnetic field, recording its intensity and direction at that moment.
Southern Africa lies within the South Atlantic Anomaly, a particularly weak patch in the magnetic field, larger than the United States. If it grows large enough, according to University of Rochester geophysicist John Tarduno, it could trigger a reversal of the poles. Understanding how the magnetic field, especially in southern Africa, has changed over time might help scientists better comprehend these processes, since there has not been much good historical data on the southern magnetic field. Because of Iron Age superstition, Tarduno and his colleagues now have a record of the anomaly for between 1,600 and 1,000 years ago.
The findings show that during the Iron Age, the magnetic field was as it is today: weakening, with a big southern dent.
