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Iron Age Remains and Earth's Magnetic Field: Key to Southern Africa Connection

Jul 29, 2015 08:15 PM EDT

A team of researchers, having analyzed deposits from fires set by agricultural workers in the Iron Age in southern Africa (between 1000 and 1500 AD), say the data left by ancient ritualistic burnings of cleared-out villages show that the Earth's magnetic field weakened dramatically in the past without flipping. This suggests that the current weakening of the Earth's field might not lead to a pole switch either, a release noted.

The data also may suggest that the region of core beneath southern Africa may have a role in reversals of the planet's magnetic poles, said the release.

Led by geophysicist John Tarduno of the University of Rochester (UR), scientists at Witwatersrand University and Kwa-Zulu Natal University of South Africa and others at UR recently published their findings in the journal Nature Communications.

Reversals of the north and south poles have occurred throughout history--the last took place about 800,000 years ago. Once started, they can take 15,000 years to complete. These scientists say the core region below southern Africa may be the origin of some of the more recent--and future--pole reversals, as the release said.

"It has long been thought reversals start at random locations, but our study suggests this may not be the case," said Tarduno, a leading expert on Earth's magnetic field, in the release.

One of the central findings is that the core beneath that region of Africa is covered by a dense and hot mantle rock that lies 1500 miles below the surface, has steep sides, and is 1864 miles across, about the distance from New York to Paris, according to the release.

The team theorizes that the region--called Large Low Shear Velocity Province--influences the direction of the liquid iron that moves below and generates Earth's magnetic field. When that flow shifts, the magnetic intensity shifts, the release said. 

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