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Earth currently hosts one of the most intriguing areas of its magnetic field over Brazil, but a new study indicates that this anomaly did not originate where it is now: it would have started in the Indian Ocean around the year 1100, crossed Africa, and slowly migrated to South America, repeating a path that has appeared at other times over the last two thousand years.
Earth has a weaker magnetic field region over Brazil and the South Atlantic known as the South Atlantic Magnetic Anomaly, and research published in PNAS indicates that the phenomenon began in the Indian Ocean about 900 years ago, migrated westward, crossed Africa, and eventually settled over South America. The work reinforces that the current anomaly is not an isolated event, but part of a recurrent behavior of the geomagnetic field.
According to the portal Olhar Digital, the detail that makes the discovery even more curious is that this “hole” in Earth‘s magnetic shield may be repeating an ancient route. The new model indicates that a similar anomaly had already traveled practically the same path between the years 1 and 850 AD, suggesting that the planet’s core and the region below Africa have been reproducing magnetic patterns over very long timescales.
The strongest detail lies in the nearly one-millennium journey to Brazil
The most impressive point of the study is the reconstruction of the anomaly’s displacement over the centuries. Instead of appearing directly over the South Atlantic, it would have originated in the Indian Ocean, around the 12th century, and slowly moved westward until it reached South America, where it now manifests most strongly over Brazil and neighboring areas.
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This journey helps change the interpretation of the phenomenon. The anomaly ceases to appear as a local and transient deformation and comes to be understood as part of a deep dynamic of Earth, linked to the functioning of the liquid outer core and the interactions between this core and the mantle below Africa.
The curious twist is that Earth may be repeating a very ancient path
The new work does not only point to a distant origin. It suggests repetition. According to the authors, a similar magnetic anomaly had already followed a similar trajectory many centuries before the current one, between the years 1 and 850 AD, which reinforces the hypothesis of a cyclic behavior in the geomagnetic field.
It is this point that transforms the discovery into something greater than a simple update on the magnetic field. If Earth truly repeats this type of route over time, what today seems like a regional weakness gains value as a clue about internal processes of the planet that have been reorganizing for millennia.
Ancient pottery helped tell the story hidden in the magnetic field
To reconstruct this trajectory, scientists resorted to a less intuitive but valuable type of archive: burnt archaeological materials. The study presents 41 archaeointensity determinations obtained by the Thellier–Thellier method from samples in central South America over the last two thousand years, using the fact that magnetic minerals in heated pottery record the intensity of the field at the time they were fired.
In practice, this allowed filling historical gaps and building a more robust model to track how magnetic weakening shifted over time. This combination of archaeology and geophysics is precisely what supports the thesis that the current anomaly of the Earth is part of an ancient sequence, and not an unprecedented rupture.
Why this “weak shield” matters so much for satellites and space missions
Although the anomaly has no visible effects on the daily lives of those on the surface, it is taken very seriously by space agencies. NASA explains that, over South America and the South Atlantic, the weaker magnetic field allows energetic particles to get closer to the surface than normal, increasing the risk of failures in satellites and instruments in low orbit.
ESA also highlights that the region has become particularly important for space safety, because satellites crossing this band face higher doses of radiation, which can cause malfunctions, hardware damage, and even outages. This is why the Earth‘s behavior in this area has been continuously monitored by missions like Swarm.
What this changes in the understanding of the future of Earth’s magnetic field
The discovery helps to curb an alarmist interpretation that often appears whenever the anomaly returns to the news. The study indicates recurrence and repetition of patterns, not a direct sign that a reversal of the magnetic poles is about to happen. NASA itself states that, today, the anomaly produces no visible impacts on daily life on the Earth‘s surface, although it remains relevant for in-orbit technologies.
At the same time, the latest data shows that the region continues to change. NASA had already recorded westward expansion and weakening, and ESA reported in 2025 that the anomaly has grown since 2014 in an area almost equivalent to half of continental Europe, in addition to showing faster weakening towards Africa.
What still needs to be confirmed about this ancient path repeated by the anomaly
Even with the advancement of the new model, there are still open questions. Scientists need to understand more precisely how deep structures beneath Africa control this behavior and why certain weakening routes reappear over the centuries. It will also be necessary to monitor whether the anomaly will continue to shift, maintain its current pattern, or reorganize in another way.
This is precisely where Brazil gains strategic relevance. As it is at the center of the affected area, the country occupies an important position to monitor changes in the Earth‘s magnetic field and help predict its effects on satellites, space missions, and technological infrastructure more sensitive to radiation.
In the end, what the new study shows is that the anomaly over Brazil is not just a strange weakening hovering over South America. It may be the slow repetition of a route that the Earth has traveled before, starting in the Indian Ocean, crossing Africa, and ending again over this side of the planet. And it is precisely this mixture of geological memory, deep movement, and technological risk that makes this magnetic “hole” one of the most fascinating phenomena underway in Earth’s shield.
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