The magnetic field that surrounds the Earth does more than simply make our compass needles point North and South. It acts as a shield, protecting us from harmful radiation by deflecting away charged particles sent towards us by the Sun. Were it not for this invisible like force field, our ozone would be slowly stripped away by solar winds and life as we know it would not exist.
Many may understand the North and South poles in the same way that they understand that the ground is below them and the sky above. As basic knowledge of our planet, fundamental aspects that are timeless and unchanging. But even on a daily basis, the magnetic poles do move. The magnetic North Pole travels in loops of up to 50 miles per day, and is gradually creeping northward by about 40 miles per year. Since explorers located its position in the early 19th century, it has migrated over 600 miles from Arctic Canada towards Siberia.
Over much longer periods of time, the magnetic field can completely change. Flipping over so that North becomes South, and South becomes North. These reversals are not rare phenomena, but regular occurrences that have taken place throughout the planet’s history. NASA believes that over the last 20 million years, the poles have settled into a pattern of flipping every 200,000 to 300,000 years. But with the last magnetic reversal taking place around 780,000 years ago, we are now well overdue one.
John Tarduno, Professor of Geophysics, and Vincent Hare, Postdoctoral Associate in Earth and Environmental Sciences, University of Rochester, say that an alarming decrease in the strength of the Earth’s magnetic field over the last 160 years could herald a new reversal.
"The magnetic field can completely change. Flipping over so that North becomes South, and South becomes North"
Writing in The Conversation they say that, “this collapse is centred in a huge expanse of the Southern Hemisphere, extending from Zimbabwe to Chile, known as the South Atlantic Anomaly. The magnetic field strength is so weak there that it’s a hazard for satellites that orbit above the region – the field no longer protects them from radiation which interferes with satellite electronics.”
Were a pole reversal about to take place, what could we expect? Hollywood disaster movie 2012 presented an apocalyptic vision of a planet in the throes of a polar shift. There have also been attempts to connect extended volcanism with these events.
Whilst we do not truly know what the full extent would be, there is no evidence to support these doomsday theories. Mathematical simulations suggest it could take several thousand years for a full reversal to take place. During the process the magnetic field may fall to 10% of its current strength, as well as multiple magnetic poles simultaneously existing. This instability in the magnetic field could increase the risk of cancer, affect navigation systems and the transmission of electricity, and leave us more susceptible to geomagnetic storms. But there have been hundreds of these events in the planet’s history and life has survived throughout.
We know our magnetic shield is created by the motion of molten iron in our planet’s outer core, but we do not yet know enough to predict when pole reversals will occur. However, satellite data has revealed an area of reversed polarity at the core-mantle boundary below southern Africa, which Tarduno and Hare believe is responsible for causing the South Atlantic Anomaly. They have used archaeomagnetic research, where archaeologists and geophysicists work together, to delve into its history.
They have found that over time this area of reversed polarity can grow rapidly before waning slowly. Were it to grow large enough, they believe it could trigger a full magnetic reversal. Their findings have led them to suggest that the geology of the region is affecting the flow of iron in the core below, which is in turn affecting the magnetic field. Whilst it could just be a fluctuation, it could also mean that a magnetic reversal has already begun.