The earth’s magnetic field, which scientists have been warning about for hundreds of years, will not suddenly tip over, according to a new study.
It now looks like the north magnetic pole will remain north and the south magnetic pole south – at least for a few thousand years or so.
“In a geologic time perspective, we are currently in a period of very strong geomagnetic field,” geoscientist Andreas Nilsson of Sweden’s Lund University said in an email. “There is still a long way to go before a polarity reversal.”
Nilsson is the lead author of research published this month by the National Academy of Sciences that examined a major weakness in the Earth’s magnetic field known as the South Atlantic Anomaly, or SAA.
The study finds that since the first geomagnetic observatories were established in the 1840s, Earth’s magnetic field has steadily weakened, while SAA weakness has increased over this period.
That has led some scientists to theorize that the Earth’s magnetic field is decreasing in strength just before fully reversing direction — something it has done several times in the past, according to rock strata deposited over millions of years that show previous reversals .
But the new research has revealed that large geomagnetic anomalies have occurred earlier and relatively recently in geologic time without a field reversal occurring.
Those anomalies usually fade a few hundred years later — and there’s no sign the SAA will be any different, Nilsson said.
Nilsson and his colleagues studied how Earth’s magnetic field has changed over the past 9,000 years by looking at the iron in volcanic rocks, ocean sediments and, in some cases, burned archaeological artifacts.
These include clay pots fired in ancient kilns thousands of years ago, which sometimes contain small amounts of an iron ore called magnetite. The magnetite lost its orientation as it was heated in the firing process, and the grains were remagnetized by the Earth’s magnetic field as it cooled, resulting in a record of field strength, Nilsson said.
The study shows that the current state of the Earth’s magnetic field is similar to that of about 600 BC. BC when it was dominated by two major weaknesses over the Pacific Ocean.
However, the anomalies over the Pacific disappeared in the following 1,000 years, and it’s likely the SAA will too, Nilsson said — probably in about 300 years, leaving a stronger and more even geomagnetic field.
A geomagnetic field reversal probably wouldn’t be catastrophic, but it would definitely be inconvenient.
Scientists believe the field is created by the flow of molten iron in the Earth’s core, about 1,800 miles below the surface. It acts as a shield against deadly solar radiation and also makes magnetic compasses work.
Geological studies have shown that the Earth’s magnetic field has flipped 10 times in the last 2.6 million years alone. The last time was about 780,000 years ago – an event known as the Brunhes-Matuyama inversion.
But while the process is linked to movements in the molten core, it’s not well understood — and scientists aren’t sure when the next reversal will happen.
“The Earth’s magnetic field reverses every 300 to 400,000 years on average,” explained Adrian Muxworthy, professor of terrestrial and planetary magnetism at Imperial College London, who was not involved in the study. “But it’s messy. It’s not regular. There have been periods when it hasn’t reversed for up to 30 million years, but we’re kinda due.”
The geological record of previous reversals shows that it may take 500 to 2,000 years for Earth’s magnetic field to fully reverse, gradually weakening in the predominant direction and gradually strengthening in the opposite direction, he said.
Muxworthy notes that while modern navigational systems such as the Global Positioning System (GPS) now rely on orbiting satellites, the navigational satellites themselves still rely on the geomagnetic field for their alignment.
It’s also likely that low-orbit satellites currently projected by the Earth’s magnetic field could be damaged by greater amounts of solar radiation during a field reversal, although they could be protected by heavier weight, he said.
At its weakest point, the Earth’s magnetic field would be about 20 percent of what it is now, leading to increased solar radiation at the surface for a time, although it probably wouldn’t be enough to affect life there, he said.
A curious side effect of a full field reversal, however, would be that the spectacular auroras now appearing mostly over the poles would appear across the world.
“It would actually be pretty exciting,” Muxworthy said. “The way we get the northern and southern lights now, we would see them at all latitudes, including over the equator.”
Nilsson warns that while his study of the South Atlantic anomaly suggests it will disappear without issue in a few hundred years, there’s still a chance Earth’s magnetic field is reversing, though scientists see no signs of it.
But “we can definitely be wrong,” he said.