Magnetic signatures hidden in rocks tell us a lot about Earth’s magnetic field and the shifting of continents and tectonic plates over millennia, but for some periods the geological record doesn’t make much sense.
A new analysis of rocks from one of these periods, the Ediacaran (about 630-540 million years ago), aims to solve a long-standing puzzle: Why does the magnetic record from that time show wild and chaotic changes in the magnetic field, as if the continents were moving unusually fast across the planet’s surface?
An international team of researchers led by Yale University found that this fault was not caused by strangely acting continents. It was the Earth’s magnetic field.
Related: Scientists reveal most detailed geological model of Earth’s past 100 million years
They performed a detailed, layer-by-layer analysis of volcanic rocks from the Anti-Atlas mountain region in Morocco, yielding a wealth of data that was more precise in terms of the position of the magnetic field and the dates of these changes.
Subsequent modeling of the data showed that these magnetic shifts occurred over thousands of years, not millions—even faster than previously thought. The best explanation is an erratic magnetic field around the planet, rather than tectonic plates moving unreasonably fast.
“We propose a new model of the Earth’s magnetic field that discovers structure in its variability, rather than simply dismissing it as randomly chaotic,” says geologist David Evans of Yale University.
“We have developed a new method for the statistical analysis of Ediacaran paleomagnetic data, which we believe will be the key to reliable maps of the continents and oceans of the period.”
Some rock samples used in the study. (Allie Barton)
The new data rejected some previous theories about the Ediacaran, including the idea of a true polar wander, in which the entire outer crust and mantle of the Earth moved a lot while the poles stayed in the same place.
By comparing the sedimentary rocks formed over a longer time period than the volcanic samples, the researchers observed the average positions of the magnetic poles and found that they did not shift during the Ediacaran.
Put it all together and we have the best model of how the Earth’s magnetic field has behaved during this time: pretty crazy. As for what might have caused the anomalies, scientists say the ongoing formation of the Earth’s core may have been at least partially responsible.
The researchers were able to model what the continents might have looked like during the Ediacaran. (Pierce et al., Sci. Adv.2025)
As analytical techniques improve, more and more of our planet’s history is being interpreted through the geological record we have left behind. This record not only shows the movement of rocks over long periods of time, but it can also help us understand when our planet was hit by visiting objects from space.
We know that the first complex life forms began to appear during the Ediacaran, and life on the planet looked very different than it does now. Also, it now seems that the continents were acting strangely wrong, but rather the Earth’s magnetic field. The findings can now be used for further research.
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“If the new statistical methods we propose are reliable, we can bridge the gap between older and younger periods to obtain a coherent visualization of plate tectonics spanning billions of years, from the earliest rock record to the present day,” says Evans.
The study was published in Scientific progress.