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To reconstruct this past, researchers turned to ancient ceramic shards buried in Argentina. When burned centuries ago, these objects preserved the memory of the magnetic field of the time, like small natural recorders. The 41 readings revealed that the phenomenon is neither new nor unique, but repeats every millennium.
A “hole” in Earth’s magnetic shield that passes right over Brazil has been intriguing scientists for decades, and a new study has provided important clues about its origin. The research shows that this weakness emerged under the Indian Ocean around the year 1000, slowly migrated westward, crossed Africa, and reached America, repeating a path that a similar anomaly had already traveled about a thousand years earlier.
The phenomenon is called the South Atlantic Magnetic Anomaly, or SAMA, and corresponds to the weakest and most extensive region of the entire magnetic field of the planet. The study was published in early May in the scientific journal PNAS, from the United States, by an international team led by Spanish scientists, and helps to understand whether the recent growth of this anomaly is something exceptional or just another chapter in a natural and repetitive process of Earth.
What is the South Atlantic Magnetic Anomaly
The South Atlantic Magnetic Anomaly is a kind of dent in this shield, a region where the field is weaker, located between Africa and South America, and that passes over Brazilian territory.
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In this area, ionizing particles from space can penetrate deeper into the atmosphere, getting closer to the surface. This does not pose an immediate danger to people on the ground, but it exposes satellites, spacecraft, and space missions to higher levels of radiation, which can cause failures in electronic equipment. Therefore, understanding the behavior of this anomaly is strategic for modern space technology.
Ancient ceramics as time recorders
To reconstruct the history of the anomaly, researchers used an ingenious technique called archaeomagnetism. They analyzed archaeological clay materials found in northwestern Argentina, near the current center of the anomaly, extracting 41 measurements of the magnetic field recorded in these objects.
The principle is fascinating. When a piece of ceramic is fired at high temperatures and then cools, the magnetic minerals inside align with the Earth’s magnetic field at that exact moment, preserving a kind of magnetic photograph of the era. Centuries later, by measuring this signature in the laboratory, scientists can reconstruct how the field behaved in the past, with remarkable precision.
A phenomenon that repeats every millennium
The results traced the trajectory of the current anomaly and revealed a surprising pattern. According to the study, the Amas would have emerged under the Indian Ocean around the year 1000, gradually moving west until reaching its current configuration over the South Atlantic and America. But the most impressive finding is that it was not the first to do so.
According to the researchers, another very similar magnetic anomaly traveled practically the same path, from the Indian Ocean westward, between the years 1 and 850 of our era, during the first millennium. For the study’s lead author, researcher Miriam Gómez-Paccard, from CSIC, Spain, this indicates that the Amas is probably the most recent expression of a recurring geomagnetic process, operating on scales of thousands of years.
What causes these anomalies
The Earth’s magnetic field is generated by the movement of liquid metals in the planet’s outer core, a kind of giant dynamo in constant agitation. Variations in this field, including the emergence of anomalies like the Amas, are linked to this deep dynamic, still full of mysteries for science.
One of the hypotheses raised by the study connects the phenomenon to the so-called Large Low Shear Velocity Provinces, or LLSVPs, which are two colossal rock masses located in the Earth’s lower mantle, one under Africa and the other under the Pacific Ocean. These structures would be large enough to disturb the magnetic field and help explain why the anomalies seem to always repeat in the same region of the planet. Even so, the scientists themselves acknowledge that more studies are needed to confirm the cause.
The Brazilian Contribution and Trindade Island
Brazil plays a prominent role in this investigation, not only because it hosts the anomaly over its territory. In 2024, a study published in the journal Nature by scientists from Unicamp analyzed rocks from Trindade Island, about a thousand kilometers off the coast of Espírito Santo, and showed that magnetic anomalies like the South Atlantic Anomaly have occurred on Earth for at least 10 million years.
The difference between the two studies lies in the time scale. The new Spanish study, based on ceramics, has very high temporal resolution but covers only the last few thousand years. Meanwhile, the Brazilian study, based on volcanic rocks, reaches much older time intervals, although with less detail. According to researcher Gelvam Hartmann, who participated in the Unicamp work, the two approaches complement each other, putting together different pieces of the same magnetic puzzle.
Why This Matters for the Future
Understanding whether the South Atlantic Anomaly is a transient or recurring phenomenon has practical implications. Since the anomaly affects satellites, navigation systems, and space missions, predicting its evolution helps space agencies and technology companies protect their equipment from radiation. Brazil, which has the anomaly right above its territory and invests in a space program, has a direct interest in this research.
The studies also help dispel exaggerated alarms. From time to time, rumors arise that the South Atlantic Anomaly is a sign of an imminent reversal of Earth’s magnetic poles, something that would cause chaos. However, the most recent research suggests that the current weakening is part of a natural cycle that has repeated before, without associated catastrophe, which helps to put the phenomenon in a more calm and scientific perspective.
The story of the South Atlantic Magnetic Anomaly is a reminder of how dynamic and full of mysteries the planet we inhabit is, even in layers we will never see directly. Thanks to shards of ceramics buried in Argentina and volcanic rocks from an isolated Brazilian island, scientists have been piecing together the long history of this “hole” in Earth’s magnetic shield. More than a cause for alarm, the anomaly reveals itself as a rare window to understand the deep heart of our planet.
And you, had you heard that there is a weak point in Earth’s magnetic shield right above Brazil? What did you think about knowing that ancient ceramics and rocks help unravel this mystery? Leave your comment, tell us what impressed you most about the South Atlantic Anomaly, and share the article with those who love science, space, and the enigmas of our planet.
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