Approximately 40,000 years ago, Earth’s magnetic field underwent a significant and dramatic reversal. Recent insights into this monumental event have emerged from an innovative analysis of data gathered by the European Space Agency’s Swarm satellite mission.

By integrating the satellite observations with terrestrial evidence of magnetic field dynamics, European geoscientists successfully mapped the Laschamps event. They have represented this event through an auditory composition that incorporates natural sounds, such as the creaking of wood and the rumbling of colliding rocks.

This unique auditory rendition, unveiled in 2024 by the Technical University of Denmark and the German Research Center for Geosciences, offers an unprecedented experience.

Generated by the turbulent liquid metals within Earth’s core, Earth’s magnetic field extends for tens of thousands of kilometers into space, shielding our planet by deflecting solar particles capable of stripping away the atmosphere.

Currently, the field lines form closed loops that extend from south to north above the surface, while beneath, they run in the opposite direction. However, the magnetic field occasionally undergoes random polarity reversals. Should such a reversal occur today, compasses would direct us towards the South Pole.

The last substantial reversal occurred roughly 41,000 years ago, leaving an imprint on the Laschamps lava flows in France. During this period, the magnetic field diminished to about 5% of its present strength, resulting in an influx of cosmic rays into Earth’s atmosphere.

Evidence archived in ice and marine sediments reveals isotopic signatures indicative of this heightened solar bombardment, with beryllium-10 levels reportedly doubling during the Laschamps event, as indicated by a study published last year.

Such isotopes originate when cosmic rays interact with our atmosphere, leading to ionization and degradation of the ozone layer. This event may have had repercussions on global climate conditions, influencing phenomena such as the extinction of Australia’s megafauna and shifts in human habitation patterns within caves.

“Comprehending these extreme events is crucial for preparing for their potential recurrence, enhancing space climate predictions, and evaluating their environmental and systemic impacts,” stated Sanja Panovska from the German Research Center for Geosciences.

The Laschamps reversal unfolded over a span of 250 years, maintaining its unusual orientation for approximately 440 years, during which the magnetic field may have only sustained 25% of its current strength as the north polarity gradually transitioned southward.

Recent anomalies in the magnetic field, such as the attenuation observed over the Atlantic Ocean, have sparked inquiries regarding a potential reversal in modern times. However, recent findings suggest that these anomalies do not necessarily correlate with polarity shifts.

Meanwhile, the South Atlantic anomaly is notably exposing satellites to elevated radiation levels.

Since its launch in 2013, ESA’s Swarm constellation has been integral in measuring magnetic signals from various layers of Earth—including the core, mantle, crust, oceans, ionosphere, and magnetosphere—enhancing our understanding of the geomagnetic field and its fluctuations.

An earlier version of this article was published in October 2024.