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Grain bins were ritually burned down during Africa's Iron Age. The resulting burnt patches have been used in the search for information regarding the South Atlantic Anomaly and the reversal of the Earth's magnetic poles.

Ancient Huts Provide New Information on Magnetic Pole Reversal and the South Atlantic Anomaly

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Scientists have recently reported that ancient burned patches on the ground in southern Africa provide groundbreaking information about the "weak spot" in the Earth's magnetic field - the South Atlantic Anomaly, as well as clues on the Earth's magnetic pole reversals.

The South Atlantic Anomaly is a weak spot in the Earth's shield against cosmic radiation 124 miles (200 kilometers) above ground. It is said to cause malfunctions in any satellites or spacecraft passing over it. Strangely enough,  it is a spot where the Earth's magnetic field pulls in energy particles instead of repelling them. Scientific evidence shows that it has been growing.

The new information provided by the burnt patches from five sites along South Africa's borders with Zimbabwe and Botswana, near the Limpopo River, demonstrates that the South Atlantic Anomaly has been a weak spot in the Earth's magnetic field for over 1,000 years.

Resulting from ritualistic burning of  huts in southern Africa Iron Age (1,000 - 1,850 AD) sites, the burnt patches illustrate that the popular belief in geomagnetic reversals taking place at random locations may not be true after all. Evidence suggests instead, that there may be something permanent in the location near the Earth's core - which is important for the magnetic pole reversals according to Discovery News .

In fact, the researchers have found what they believe to be the cause of the South Atlantic Anomaly. "The top of the core beneath this region is overlain by unusually hot and dense mantle rock," John Tarduno, a geophysicist from the University of Rochester in New York and the leading author of the new report, told Space.com

According to collaborator archaeologist Thomas Huffman, from Witwatersrand University in South Africa, the ritualistic burning was meant to cleanse the villages. “They had this ritualistic burning of villages,” Tarduno explained to Space.com. “Particularly in times of drought, the conclusion would be that there might have been some offence in the village, so the solution was to have a burning down of the village.”

The resulting burned patches of ground contain a specific mineral that was able to record the situation of the Earth's magnetic field during over time. As the burning villages reached high temperatures (over 1,800 degrees Fahrenheit or 1,000 degrees Celsius), magnetic compounds such as magnetite in the clay floors were melted and later re-magnetized by the Earth's magnetic field at the moment of cooling. This provides the information which scientists are able to study today.

By studying these minerals, Tarduno and his fellow researchers have confirmed that the region witnessed a 30% drop in magnetic field intensity from 1225 to 1550 AD. Tarduno stated that the South Atlantic Anomaly “forms, and it decays away, and it forms, and it decays away; eventually, one might form and get really large, and then we might actually have a geomagnetic reversal.”

Image depicting the lower magnetic surface field above corresponding with the hot dense mantle below in the South Atlantic Anomaly.

Image depicting the lower magnetic surface field above corresponding with the hot dense mantle below in the South Atlantic Anomaly. ( Michael Osadciw/University of Rochester )

Scientists have shown that the magnetic north and south poles have reversed many times in the Earth's history and the last pole reversal was about 800,000 years ago. That is actually quite a long time since the last reversal, as scientists explain that it can take up to 15,000 years for the reversal to take place after it begins. Tarduno is however hesitant to say that we are currently entering into a reversal of the magnetic field.

NASA computer simulation showing the differences of the Earth's magnetic field lines between and during a reversal of the north and south magnetic poles. The blue lines show when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core.

NASA computer simulation showing the differences of the Earth's magnetic field lines between and during a reversal of the north and south magnetic poles. The blue lines show when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core. ( Wikimedia Commons )

While he may be reluctant to make such a claim, other research has shown that the Earth's dipole magnetic field strength has, in fact, decreased 16 percent since 1840. Mostly this decreasing intensity has been located in the Southern Hemisphere, specifically in the region of the South Atlantic Anomaly.

Featured image: Grain bins were ritually burned down during Africa's Iron Age. The resulting burnt patches have been used in the search for information regarding the South Atlantic Anomaly and the reversal of the Earth's magnetic poles. ( John Tarduno/University of Rochester )

By Alicia McDermott

Comments

Might this anomaly be the result of a comet collision?

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