The protective shell of our planet is no longer quite what it used to be. Over the past two centuries, its magnetic force has been dropping, and no one knows why.
At the same time, a worrying weak spot on the ground called the South Atlantic Anomaly has crumbled over the Atlantic Ocean and has already proved problematic for the delicate circuitry of orbiting satellites.
Both of these disturbing observations fuel concerns that we could see signs of an impending reconfiguration that would turn the cardinal points upside down in what is known as a magnetic pole reversal.
But researchers behind a new survey modeling the planet’s magnetic field in the recent past warn that we shouldn’t be too hasty in assuming this is going to happen.
“Based on the similarities to the recreated anomalies, we predict that the South Atlantic Anomaly will likely disappear within the next 300 years and that Earth is not heading towards a polarity reversal,” says geologist Andreas Nilsson of Lund University in Sweden.
Not anytime soon, at least. So for now we can breathe easy.
Yet, based on our geological history, it is likely that the flowing lines of our planetary magnetic field will eventually indicate the opposite.
What such a reversal would mean for humanity is unclear. The last time such a monumental event occurred, just 42,000 years ago, life on Earth seemed to be going through a rough patch as a shower of high-speed charged particles swept through our atmosphere.
Whether we humans noticed this – perhaps reacting by spending a bit more time in the shelter – is a matter of speculation.
However, given the current reliance on electronic technology that could be vulnerable without the protection of a magnetic umbrella, even the fastest field reversals for the foreseeable future would leave us exposed.
Geologists are therefore keen to know which tremors, wobbles and wanderings in the field herald disaster and which imply the status quo.
Much of what we know about the history of the magnetic field comes from how its orientation forces particles in molten materials to align before being locked in place as they solidify. Digging through layers of mineralized arrowheads provides a fairly clear record of where the compass has pointed over the millennia.
Likewise, pottery artifacts from archaeological sites may also provide a snapshot of the field in more recent times, capturing its direction in clay before firing.
In the new study, researchers from Lund University and Oregon State University pieced together a detailed timeline of our planet’s magnetic shell dating back to the last Ice Age, by analyzing samples of volcanic rocks, sediments and artifacts from around the world.
“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 likely recurring phenomena linked to corresponding changes in the strength of the Earth’s magnetic field,” says Nilsson.
With thousands of years of perspective, it quickly becomes clear that the weak spot in the South Atlantic is not completely out of the ordinary. Starting around 1600 BCE, a similar geological shift took place, lasting around 1300 years before fading away once again.
Assuming the same basic mechanics are at work, it’s likely that the current debuff patch will soon regain strength and fade without ending in a global reconfiguration. It is even likely that the magnetic field as a whole will regain a vigor that we have not seen since the beginning of the 19th century.
However, this is not evidence against a reversal that will occur soon – just new evidence suggesting that we should not interpret the current anomalies of waning strength as strong signs of a polar reversal.
In some ways, this is good news. But that leaves us in the dark about what exactly such a massive geological process will look like on the scale of a human lifetime.
Having detailed records like this goes a long way in building a clearer picture, so maybe if the worst should happen we’ll be prepared for it.
This research was published in PNAS.