The emergence of a mysterious area in the South Atlantic where geomagnetic field strength is decreasing rapidly, has led some to speculate Earth’s magnetic poles are about to ‘flip’.
This would see Earth’s magnetic field switch from north to south, and some believe it could bring chaos to our wired world.
But a study, based on evidence stretching back 9,000 years, has suggested that a reversal may not be in the cards after all – and that the ‘anomaly’ which triggered the speculation will instead vanish.
Earth’s magnetic field acts as an invisible shield against the life-threatening environment in space, and solar winds that would otherwise sweep away the atmosphere.
But the magnetic field is not stable, and every 200,000 or so years polarity reversals happen, meaning that the magnetic North and South poles swap places.
During the past 180 years, Earth’s magnetic field strength has decreased by about 10%.
Lead author Andreas Nilsson, a geologist at Lund University, said, “We have mapped changes in the Earth’s magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are probably recurring phenomena linked to corresponding variations in the strength of the Earth’s magnetic field.
This area, where satellites have malfunctioned several times due to exposure to highly charged particles from the sun, is called the South Atlantic anomaly.
The results are based on analyses of burnt archaeological artefacts, volcanic samples and sediment drill cores, all of which carry information about the Earth’s magnetic field.
These include clay pots that have been heated up to over 580ºC, volcanic lava that has solidified, and sediments that have been deposited in lakes or in the sea.
The objects act as time capsules and carry information about the magnetic field in the past.
Using sensitive instruments, the researchers have been able to measure these magnetisations and recreate the direction and strength of the magnetic field at specific places and times.
“We have developed a new modelling technique that connects these indirect observations from different time periods and locations into one global reconstruction of the magnetic field over the past 9,000 years”, Nilsson said.
“Based on similarities with the recreated anomalies, we predict that the South Atlantic Anomaly will probably disappear within the next 300 years, and that Earth is not heading towards a polarity reversal.”
By studying how the magnetic field has changed, researchers can learn more about the underlying processes in the Earth’s core that generate the field.
The new model can also be used to date both archaeological and geological records, by comparing measured and modelled variations in the magnetic field.
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