A new study has revealed that Earth’s geomagnetic field, which scientists warned about hundreds of years ago, will not suddenly reverse.
It now appears that the north pole of the magnet will remain north and the south pole of the magnet will remain south – at least for a few thousand years or more.
“From a geological time perspective, we are currently in a period of very strong geomagnetic fields,” geologist Andreas Nilsson of Sweden’s Lund University said in an email. “So there’s still a long way to go before the polarity reversal.”
Nelson is the lead author of this study Posted this month by the National Academy of Sciences which studied the significant attenuation of the geomagnetic field known as the South Atlantic Anomaly, or SAA.
Studies show that Earth’s magnetic field has been getting weaker since its inception geomagnetic observatory It was founded in the 1840s, while the SAA’s weaknesses have grown bigger during that time.
This has led some scientists to theorize that the geomagnetic field declined sharply before completely reversing direction—something that has been done many times in the past, according to layers of rock formed over millions of years that show a reversal in the past.
But new research finds that large geomagnetic anomalies have occurred before, and relatively recently in geological time, without causing a field reversal.
These anomalies usually fade 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, marine sediments, and in some cases, burned artifacts.
These include clay pots burned in ancient kilns thousands of years ago, which sometimes contain small amounts of an iron ore called magnetite. The magnetite loses alignment when heated in the combustion process, and the grains are magnetized again by the geomagnetic field as they cool, recording the strength of the field, Nelson said.
Studies show that the state of the Earth’s magnetic field today is similar to around 600 BC, when it was dominated by two large weak spots over the Pacific Ocean.
Over the next 1,000 years, anomalies around the Pacific Ocean fade, Nelson said, and it’s likely that SAA will too — perhaps in about 300 years, leaving Earth’s magnetic field stronger and stronger.
The reversal of Earth’s magnetic field probably wouldn’t be catastrophic, but it certainly would be troublesome.
Scientists believe these fields are 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 lethal solar radiation, and also keeps the magnetic compass working.
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 even though the process is linked to motion in the molten core, it’s not well understood — and scientists aren’t sure when the next reversal will occur.
“Earth’s magnetic field reverses on average every 300,000 to 400,000 years,” explains Adrian Muxworthy, professor of Earth and planetary magnetism at Imperial College London, who was not involved in the study. “But it’s a mess. It’s erratic. There’s a period where it hasn’t subsided to 30 million years, but we deserved it.”
He said the geological record of past reversals shows that Earth’s magnetic field could take between 500 and 2,000 years to completely reverse by growing weaker in the dominant direction, and stronger in the opposite direction.
Muxworthy notes that while modern navigation systems, such as the Global Positioning System (GPS), now rely on orbiting satellites, the navigation satellites themselves still rely on geomagnetic fields to align them.
It’s also possible that satellites in lower orbits predicted by Earth’s current magnetic field could be damaged by greater amounts of solar radiation during a field reversal, although 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 today, which for some time could lead to an increase in solar radiation at the surface, although it may not be enough to affect life there.
However, one odd side effect of a full-terrain inversion is that the spectacular aurora borealis now occurring mainly over the poles will occur worldwide.
“It’s actually going to be really interesting stuff,” Moxworthy said. “Just as we are now getting northern and southern auroras, we have seen them at all latitudes, including over the equator.”
Nelson warns that while his studies of the South Atlantic anomaly suggest that it will fade without issue within a few hundred years, there is still the possibility that Earth’s magnetic field will begin to reverse, even though scientists see no sign of that.
But he said, “We can definitely be wrong.”
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