Earth's magnetic field is constantly shifting, and roughly every 200,000 to 300,000 years it flips north and south completely. We're currently overdue for a switcheroo—and scientists now say it could happen in a time as short as 100 years, potentially altering life in unexpected ways.
It was long thought that these reversals took as many as 7,000 years to completely switch, according to a 2004 study funded by the National Science Foundation. But over the past few years, other scientists have suggested that the shifts have occurred at speeds previously unimagined. And a brand-new study published in the Geophysical Journal International by a team of scientists from Europe and the U.S. sheds even more light on these speedy changes—suggesting that the last 180-degree flip only took about 100 years.
How did they discern changes in the magnetic field that date back hundreds of thousands of years? By testing layers of ash deposited by volcanic eruptions over the course of 10,000 years, found in a lakebed near Rome. According to a release from Berkeley, the magnetic field directions are "frozen" into these layers of ash, which could be reliably dated to find out when the reversals occurred and how long they took to complete. "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," said Berkely's Paul Renne, one of the study's authors.
"This map shows how, starting about 789,000 years ago, the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the pole somewhere in the Arctic." Via Berkeley.
We've known for a long time that the Earth's magnetic field is shifting, We know, for example, that the North Pole has moved 600 miles in the last 200 or so years. We also know that, as observed by three ESA satellites this summer, the Earth's magnetic field is weakening in some areas and strengthening in others. We also know that the shifting currents are already necessitating some changes in our human world: Airports that name their runways after compass directions have recently been forced to rename and repaint due to the shift.
So it's no surprise that a flip may be imminent—more so that a true, full reversal could happen so quickly. And, as the study suggests, how it could actually change the way we live on Earth. For example, a weakened field means less protection for humans against harmful rays that cause cancer, meaning that the cancer rate would likely increase. And the infrastructural impact of a flipped field could be massive, too, causing problems with the electricity grid and other sensitive systems.
For us short-lived humans, these changes are normally unthinkably geologic in scale. It's fascinating to learn that though we likely won't be witness to a shift of this magnitude, it's within the realm of possibility that some other homo sapiens might. [Berkeley]