A new study has revealed that Earth’s geomagnetic field, which scientists warned about hundreds of years ago, isn’t about to suddenly flip after all.
It now appears that the magnetic north pole will remain in the north and the magnetic south pole will remain in the south – at least for a few thousand years or so.
“From a geological time perspective, we are currently in a period of a very strong geomagnetic field,” geologist Andreas Nilsson of Sweden’s Lund University said in an email. “So there is a long way to go before the polarity reversal.”
Nelson is the lead author of the research Posted this month by the National Academy of Sciences that studied a significant weakening of the geomagnetic field known as the South Atlantic Anomaly, or SAA.
The study indicates that the Earth’s magnetic field is getting weaker from the start geomagnetic observatories It was founded in the 1840s, while the SAA’s weakness has grown even larger during that time.
This led some scientists to theorize that the geomagnetic field decreases strongly before it completely reverses direction—something it has done many times in the past, according to layers of rock laid down over millions of years that show past reversals.
But the new research finds that large geomagnetic anomalies have occurred before, and relatively recently in geologic time, without causing a field reversal.
These anomalies usually fade away after a few hundred years — and there’s no indication that SAA will be any different, Nelson said.
Nelson and his colleagues studied how Earth’s magnetic field has changed over the past 9,000 years by looking at iron in volcanic rocks, ocean sediments, and in some cases, burnt artefacts.
These include clay pots fired in ancient kilns thousands of years ago, which sometimes contain small amounts of iron ore called magnetite. The magnetite lost its alignment when it was heated up in the firing process, and the grains became magnetized again by the geomagnetic field when they cooled, recording the strength of the field, Nelson said.
The study shows that the current state of the Earth’s magnetic field is similar to around 600 BC, when it was dominated by two large weak points over the Pacific Ocean.
Over the next 1,000 years, the anomaly around the Pacific Ocean faded away, Nelson said, and likely the SAA will as well — perhaps in about 300 years, leaving a stronger and more powerful Earth’s magnetic field.
The reversal of the Earth’s magnetic field would probably not be catastrophic, but it would certainly be inconvenient.
Scientists believe this field is caused by the flow of molten iron into the Earth’s core, about 1,800 miles below the surface. It serves as a shield against deadly solar radiation, and it also makes magnetic compasses work.
Geological studies have shown that the Earth’s magnetic field has reversed 10 times in just the last 2.6 million years. The last time was about 780,000 years ago – an event known as the Brunhes-Matuyama reversal.
But although 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 occur.
“The Earth’s magnetic field reverses on average every 300,000 to 400,000 years,” explained Adrian Muxworthy, professor of Earth and planetary magnetism at Imperial College London, who was not involved in the study. “But it’s chaotic. It’s erratic. There have been periods where it hasn’t receded for up to 30 million years, but we kind of deserved it.”
He said geological records of past reversals show that Earth’s magnetic field could take anywhere from 500 to 2,000 years to completely reverse by growing progressively weaker in the dominant direction, and progressively stronger in the opposite direction.
Muxworthy notes that while modern navigation systems, such as the Global Positioning System (GPS), now rely on orbiting satellites, navigational satellites themselves still rely on the geomagnetic field to align them.
It’s also possible that satellites in the lower orbits that Earth’s magnetic field currently expects could be damaged by greater amounts of solar radiation during field reversal, though they could be protected by making them heavier, he said.
He said the geomagnetic field at its weakest would be about 20 percent of what it is now, which for some time could lead to increased solar radiation at the surface, although perhaps not enough to affect life there.
However, one strange side effect of full-field inversion is that the spectacular aurora borealis that now occurs mainly over the poles will occur worldwide.
“It’s actually going to be a very exciting thing,” Moxworthy said. “Just as we now get the northern and southern aurora, we’ve been seeing them at all latitudes, including above the equator.”
Nelson cautions that while his study of the South Atlantic anomaly suggests that it will fade without problems within a few hundred years, there is still a possibility that Earth’s magnetic field will begin to reverse anyway, although scientists see no sign of that.
But he said, “We can certainly be wrong.”
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