What if north became south and south became north? Although it sounds unlikely, it's actually happened before, when the Earth's magnetic fields flipped.
In fact, it's happened many times in the Earth's history, including around 780,000 years ago. And it's about to happen again, within a few thousand years.
This flip, however, is not a slow and gradual process. In fact, it happens relatively quickly, within 100 years, about the span of a human lifetime. We now know this, thanks to research by an international team of scientists that studied evidence from the last magnetic flip.
"It's amazing how rapidly we see that reversal," says Courtney Sprain, a UC Berkeley graduate student. "This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen."
The Earth's magnetic field is dipole; it's a lot like a bar magnet that has two opposite poles. Those poles hold steady for thousands, even millions of years, but then, for no known reason, they weaken and reverse direction.
How did we learn how rapid this reversal really is? Scientists studied layers of ancient lake sediments in Italy and measured their alignment with the Earth's magnetic fields. Using argon-argon dating, scientists determined the ages of rocks in each layer.
The results of these measurements showed that the transition of the last magnetic field switch happened approximately 786,000 years ago and took about 100 years for completion.
"What's incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years," says Paul Renne, a UC Berkeley professor-in-residence of earth and planetary science. "We don't know whether the next reversal will occur as suddenly as this one did, but we also don't know that it won't."
Although there is no historical evidence that such magnetic flips affect the environment or the Earth's inhabitants, scientists fear that the next flip will create electrical currents that could disrupt electrical power grids and communications technology. The weakening of the fields could also lead to higher rates of cancer because the Earth's magnetic field currently protects us from the sun's rays, along with cosmic rays. A weakened magnetic field allows more of these rays in, causing genetic mutations, such as cancer.
As it stands, the Earth's magnetic field is currently weakening 10 times faster than expected, indicating an imminent pole flip, so more research like this can help us understand how and why this phenomenon happens.
