A new paleomagnetic study of volcanic rocks in Morocco's Anti-Atlas shows that apparently chaotic Ediacaran magnetic signals (about 630–540 million years ago) reflect rapid changes in the geomagnetic field, occurring over thousands of years rather than millions. The team’s higher-resolution sampling and statistical methods indicate an unusually unstable global magnetic field rather than extreme continental motion. Their results weaken true polar wander explanations and suggest core evolution may have driven the anomalies. If robust, the approach could improve tectonic reconstructions spanning deep time.
500-Million-Year-Old Magnetic Mystery Solved: Ediacaran Field Was Unusually Unstable
A new paleomagnetic study of volcanic rocks in Morocco's Anti-Atlas shows that apparently chaotic Ediacaran magnetic signals (about 630–540 million years ago) reflect rapid changes in the geomagnetic field, occurring over thousands of years rather than millions. The team’s higher-resolution sampling and statistical methods indicate an unusually unstable global magnetic field rather than extreme continental motion. Their results weaken true polar wander explanations and suggest core evolution may have driven the anomalies. If robust, the approach could improve tectonic reconstructions spanning deep time.
18:11, 02.11.2025Science
A Giant Magnetic Anomaly Over 500 Million Years Ago — Explained
Hidden magnetic signatures locked in ancient rocks record the behavior of Earth's magnetic field and the motions of continents over geological time. For the Ediacaran period (about 630–540 million years ago), however, paleomagnetic data long appeared chaotic, suggesting implausibly rapid continental motion.
New study and methods
An international team led by Yale University reexamined this puzzling interval by carrying out dense, layer-by-layer paleomagnetic sampling of volcanic sequences in Morocco's Anti-Atlas mountains. Using much finer stratigraphic resolution and improved dating, they produced a more precise dataset of ancient field directions and apparent pole positions than previously available.
What the data show
When the team modeled the new measurements, the apparent pole jumps resolved into changes that occurred over thousands of years rather than millions. Those rates are far too rapid to reflect sudden continental drift or plate motions. Instead, the simplest and best-supported interpretation is that the geomagnetic field itself was highly unstable during parts of the Ediacaran.
"We are proposing a new model for the Earth's magnetic field that finds 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 of statistical analysis of Ediacaran paleomagnetic data that we think will hold the key to producing robust maps of the continents and oceans from that period," Evans adds.
Ruling out alternative explanations
The new analysis also undermines several earlier hypotheses, including true polar wander — the idea that Earth’s outer shell rotated wholesale while geographic poles remained fixed. By comparing volcanic sequences (short-lived records) with longer-lived sedimentary averages, the researchers found little net pole migration across the Ediacaran as a whole, consistent with a fluctuating field rather than wholesale crustal reorientation.
Possible causes and implications
The authors suggest that continuing evolution of Earth's core and the geodynamo may have driven the unusual field behavior. If confirmed, these findings refine how geologists read the rock record and can improve reconstructions of plate motions deep in Earth history.
Clarifying geomagnetic behavior during the Ediacaran is particularly important because this interval witnessed the emergence of some of the first complex multicellular life. Better magnetic reconstructions provide context for the environments in which early complex organisms evolved.
The study is published in Science Advances.