Our planet’s protective shell is not quite what it used to be. Over the last two centuries, its magnetic force has taken a deep dive, and no one has any idea why.
At the same time, a worryingly soft spot in the field called South Atlantic Anomaly has blown across the Atlantic, and has already proved problematic for delicate orbits on orbital satellites.
Both of these disturbing observations give rise to concerns that we may see signs of an impending reconfiguration that will turn the compass points completely into what is known as a magnetic pole reversal.
But scientists behind a recent study that models the planet’s magnetic field recently warn that we should not be too hasty in assuming that it will happen.
– Based on similarities with the recreated anomalies, we predict that the South Atlantic anomaly will probably disappear within the next 300 years, and that the Earth is not heading for a polarity reversal, says geologist Andreas Nilsson from Lund University in Sweden.
Not soon, at least. So for now, we can breathe easy.
Nevertheless, if our geological history is anything to go by, it is likely that the floating lines in our planetary magnetic field will eventually point the other way around.
What such a reversal will mean for humanity is not clear. The last time such a monumental event took place, just 42,000 years ago, it seemed that life on Earth was going through a tough period when a rain of high-velocity-charged particles tore through our atmosphere.
Whether we humans noticed – perhaps responding by spending a little more time in shelter – is a matter of speculation.
But given today’s reliance on electronic technology that can be vulnerable without the protection of a magnetic umbrella, even the fastest field reversals in the foreseeable future will leave us vulnerable.
So geologists are interested in knowing which hesitations, hesitations and wanderings in the field that herald disaster, and which involve business as usual.
Much of what we know about the history of the magnetic field comes from the way its orientation forces particles in molten materials to line up before being locked in place when they solidify. Digging through layers of mineralized arrows provides a fairly clear overview of which path the compass pointed through the millennia.
In the same way, ceramic map facts from archeological sites can also give a snapshot of the field in recent times, and capture the direction in clay before firing.
In the new study, researchers from Lund University and Oregon State University reconstructed a detailed timeline of the planet’s magnetic shells dating back to the last ice age, by analyzing samples of volcanic rocks, sediments and objects from around the world.
– We have mapped changes in the earth’s magnetic field in the last 9000 years, and anomalies such as the one in the South Atlantic are probably recurring phenomena related to similar variations in the strength of the earth’s magnetic field, Nilsson says.
With thousands of years of perspective, it quickly becomes clear that the South Atlantic soft spot is not completely out of the ordinary. From around 1600 BC. a similar geological change took place, which lasted about 1300 years before it was left out again.
Assuming the same basic mechanics are at work, it is likely that the current weakening will soon regain strength and disappear without ending in global reconfiguration. It is even likely that the magnetic field as a whole will bounce back to a force we have not seen since the early 1800s.
However, this is not proof that a reversal will happen soon – only new evidence that suggests that we should not interpret current anomalies of diminishing strength as strong signs of a polar flip.
In some ways, that’s good news. But it leaves us in the dark about exactly what such a massive geological process will look like in the scope of a person’s life.
Having detailed records like this goes a long way toward building a clearer picture, so maybe if the worst happens, we’ll be prepared for it.
This research was published in PNAS.