Something is wrong above our heads. The Earth's magnetic field is dramatically weakening - and, according to new research, this phenomenal weakening is part of an action that has been going on for more than 1000 years.
The Earth's magnetic field doesn't just give us our north and south poles; it also protects us from solar winds and cosmic radiation, but this invisible force field is rapidly weakening, and now scientists believe that it can actually flip, and our magnetic poles will swap.
As incredible as it may sound, in fact, such pole shifts occur over huge periods of time. The last time this happened was about 780,000 years ago.
When it does, it doesn't happen quickly, with a gradual polarity reversal over thousands of years.
No one knows for sure if another such coup is really inevitable.
The region that worries scientists is now known as the "South Atlantic Anomaly," a vast area stretching from Chile to Zimbabwe. The magnetic field is so weak in this zone that it is dangerous for Earth satellites, because the additional radiation that it passes through can destroy their electronics.
“We've known for a long time that the magnetic field is changing, but we don't know if this was unusual for this region for a long period of time, or if it was normal,” says physicist Vincent Hare of the University of Rochester in New York.
One of the reasons why scientists know little about the magnetic history of this region of the Earth is the lack of archaeomagnetic data - physical evidence of magnetism in the past, preserved in archaeological relics from the last century.
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One such bygone era belongs to a group of ancient Africans who lived in the Limpopo River Valley, which borders Zimbabwe, South Africa and Botswana: regions that are today in the South Atlantic.
Roughly 1,000 years ago, these Bantu peoples observed a complex, superstitious ritual during times of environmental hardship.
During a drought, they burned their clay huts and grain bins in a sacred rite so that the rains would come again - without even assuming that they had been doing preparatory scientific research for scientists for several centuries.
“When you burn clay at very high temperatures, you actually stabilize the magnetic minerals, and when they cool down, they record a record of the earth’s magnetic field,” explains geophysicist John Tarduno.
Thus, analysis of surviving ancient artifacts reveals much more than just the cultural customs of the ancestors of modern South Africans.
“We looked for the repetitive behavior of the anomalies, because in our opinion, this is what is happening today and is causing the anomaly in the South Atlantic,” says Tarduno.
“We found evidence that these anomalies happened in the past, and this helps us to contextualize the current magnetic field changes.”
Like a "compass frozen in time," the artifacts showed that field weakening in the South Atlantic Anomaly is not a separate historical phenomenon.
Similar fluctuations occurred in the years 400-450. AD, 700-750 A. D. and 1225-1550. A. D. - and this fact suggests that the position of the South Atlantic anomaly is not a geographic accident.
“We are witnessing that Africa has some kind of unusual border that could have an important impact on the global magnetic field,” says Tarduno.
We still have a lot of research to do before we know more about what's going on here.
As the researchers explain, the idea behind the reversal of the poles is that they can start anywhere in the core, but recent results show that this happens in a magnetic field above us, and is tied to phenomena in special places on the border of the core and mantle.
“We now know that this unusual field behavior has occurred at least a couple of times before the last 160 years and is part of a longer-term pattern,” says Hare.
"It is too early, however, to say for sure if this behavior will lead to a complete reversal of the poles."
The results are presented in Geophysical Review Letters.