A new discovery is providing insight into the magnetic field activity of the Earth in ancient times.
For the first time, scientists have recovered a record of magnetic field in ancient minerals in the Iron Age of southern Africa. They found that with the Earth's currently weakening magnetic field, a portion of the Earth's core found in the south African region potentially plays a special role in the reversals of the magnetic poles.
Led by University of Rochester physicist John Tarduno, the research team from Rochester, Kwa-Zulu Natal University of South Africa and Witwatersrand University gathered data found in five sites in an area that has a weak magnetic field: the South Atlantic Anomaly, located along the border of South Africa with Botswana and Zimbabwe.
The researchers found that the ritualistic burning in villages in the Iron Age of South Africa not only suggests the Earth's core had an important role in magnetic reversals, but also points to it as the "birthplace" of some of the more recent, and even the future, reversals of poles.
The reversals of the Earth's magnetic fields occur irregularly. A reversal was last recorded around 800,000 years ago, and an entire shift may take 15,000 years to complete. Since 1940, the Earth's magnetic field has been weakening by about 16 percent. Experts say this may turn into a reversal sooner or later.
A reason why the Earth's magnetic field is weakening may be because of a flow shift in the liquid iron metal that generates the field. According to Tarduno, such irregularities may eventually lead to a decrease or further, a loss, in magnetic intensity, giving the region a low magnetic field strength.
The evidence of the remains of the South African ritualistic village burnings led to a decrease in magnetic field intensity to about 30 percent from 1225 AD to 1550 AD. The researchers believe that such changes in behavior may be a recurring feature of the region.
In the ancient villages of South Africa, the burnt clay floors caused temperatures to go over 1,000 degrees C. At the time, while burning occurred, the temperature may have risen to a level so high that the magnetic field information was replaced with a new record of the strength and direction of the magnetic field.
Findings of the research are published in Nature Communications.
