- 3232 - EARTH - what is its magnetic future? - The strength of Earth’s magnetic field has already been dropping over the past 1,000 years, and if the “South Atlantic Anomaly” grew and took over, we’d have a field reversal. The North Pole would become the magnetic South Pole. Your compass would flip.
------------------ 3232 - EARTH - what is its magnetic future?
- In the South Atlantic, stretching from Chile to South Africa, there’s a wide span where the Earth’s magnetic field isn’t quite in line with the rest of the Earth. Here, at what’s called the “South Atlantic Anomaly“, the field is weak. It’s so weak that it affects the satellites passing over because they are bombarded by solar radiation and space debris that are usually held off by the magnetic field.
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- This patch of low magnetism is growing. Underneath the surface, at the core-mantle boundary, it appears there are patches where the field has actually flipped polarity, that is the field north-south has is reversed. These are sometimes called “reverse flux patches“.
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- Some geologists are concerned that if the patch grows too big, it could trigger a sudden collapse of the field or even a flip of Earth’s magnetic poles. If this were to happen, electrical grids and satellite technologies would be at risk. The North Pole compass would be pointing south.
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- In a 2021 study, paleomagnetists, researchers who study the history of Earth’s changing geomagnetic field found evidence that a sharp directional change and intensity dip occurred around 1,100 –1,300 B.C. in what is today Cambodia. This means the area may have experienced a geomagnetic “twitch” not unlike the South Atlantic Anomaly we see today.
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- Earth’s magnetic field acts as if there’s a giant bar magnet inside. It is why compasses point toward the North Pole. It is created by the liquid iron in Earth’s core. But the field is more complicated than that. There are spots where it’s stronger or weaker than the bar magnet would explain, and spots where the direction is out of line with north-south.
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- As these patches wax and wane, they affect the field as a whole sometimes even causing the magnetic north and south poles to flip entirely, which has happened every million years or so.
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- Are we headed for a flip now? It’s not out of the question. To understand Earth’s future, researchers look to its past. Paleomagnetists look for materials that were heated to high temperatures and then cooled, like lava, or clay pots fired in a kiln.
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- When materials are brought to a high enough temperature, the magnetic molecules inside lose their magnetism. As they cool back down, the molecules not only become magnetized proportionally to the strength of the Earth’s magnetic field, but also are more likely to point in the direction of the field.
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- This, combined with radiocarbon dating, allows researchers to measure the intensity and direction of the past field from artifacts and rocks.
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- Archaeologists are excavating a site near the ancient city of Angkor in Cambodia. The area was once host to ancient iron-smelting operations centered around a huge hematite deposit, Phnom Dek, which in Kmerian means “iron mountain.”
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- The researchers excavated a site called Tonle Bak that was active around the time when Angkor was starting to rise and the Khmer Empire was starting to gain power, between the 11th and 13th centuries.
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- The archaeological team was interested in the interplay between the widespread iron smelting and the rise of the empire. But the excavations also provided a unique opportunity to reveal information about the Earth’s geomagnetism.
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- Iron production sites are valuable to geomagnetic research since they once produced massive amounts of waste that was heated. Finding a smelting furnace is better than something like a clay pot, since it’s attached to the landscape, meaning it’s still facing the same direction it was when it was heated and then cooled, so the direction of the magnetic field when it was heated is preserved.
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- At Tonle Bak, they found three iron furnaces, the first ever found in Cambodia.
This is the first time researchers have uncovered paleomagnetic data from this area and one of the first data points from near the equator.
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- The researchers found that the rate of directional change from 1200 to 1300 B.C. was about 10 times what’s happening today, and the intensity of the geomagnetic field dropped sharply between 1,100 and 1,300 B.C. It’s reminiscent of today’s South Atlantic Anomaly.
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- There’s no evidence that the patch caused any problems for society at the time. Reverse flux patches, or spots where the Earth’s geomagnetic field is twisted , are something scientists are still working to understand, especially when it comes to how they can affect the field as a whole.
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- The strength of Earth’s magnetic field has already been dropping over the past 1,000 years, and if the South Atlantic Anomaly grew and took over, we’d have a field reversal.
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- Researches recovered high-fidelity full-vector geomagnetic information from the 11th to 14th century for this region, which fill gaps in the global distribution of data and will significantly improve the global models.
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- These results reveal a sharp directional change of the geomagnetic field between 1,200 and 1,300 B.C., accompanied by an intensity dip between 1,100 and 1,300 B.C.. The fast geomagnetic variation recorded by our data provides evidence for the possible existence of low-latitude flux expulsion. What’s next?
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- July 26, 2021 EARTH - what is its magnetic future? 3232
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