Context:

A team of researchers is currently recreating the Brunhes-Matuyama reversal—one of the most significant geomagnetic events in Earth's history, which occurred about 780,000 years ago. During this event, the Earth’s magnetic polarity flipped completely and remained reversed for over 100,000 years. The team is also converting data from this reversal into sound, a process called sonification. A soundtrack of the event is expected later this year.

About Earth’s Magnetic Field

• Earth’s magnetic field originates about 2,900 km below the surface, in the liquid outer core. As molten iron moves—powered by heat from the solid inner core and planetary rotation—it generates electric currents, giving rise to the geomagnetic field. This flow is inherently unstable, and its changing dynamics are what cause fluctuations, reversals, or excursions. Clockwise fluid movement results in normal polarity, while a reversal of flow direction induces a polarity flip.
• Over the past 200 years, Earth’s magnetic field strength has weakened by about 10%. If this rate of decline continues, models estimate the field could drop to zero within 1,500–1,600 years, raising questions about whether another reversal or excursion might be imminent.

Reversals and Excursions

When the magnetic poles switch and stay reversed for over 100,000 years, the event is called a reversal. If the change is brief and the poles return to their original positions sooner, it is called an excursion.

Scientists have recorded 183 full reversals in the last 83 million years. Since the Brunhes-Matuyama reversal, three major excursions have occurred:

• Norwegian-Greenland Sea Event (64,500 years ago)
• Laschamps Excursion (41,000 years ago)
• Mono Lake Excursion (34,500 years ago)

Despite extensive research, scientists cannot predict when the next reversal or excursion will happen as they happen without periodicity. Some studies link excursions to climate changes or ozone depletion, but others argue their effects on life are minimal. Additionally Earth's atmosphere may still shield us from radiation during these events.

Clues from Rocks and Records:

To understand magnetic history, scientists use various sources:

• Satellite data and geomagnetic observatories for current field behavior
•  Historical ship logs (dating to 1590) for past changes
•  Volcanic rocks, lake sediments, and pottery, which preserve magnetic directions like natural recorders

In India, researchers found evidence of an excursion from 15,500 years ago in the Nanda Devi Biosphere Reserve, Uttarakhand, through sediment analysis. This adds to global studies on geomagnetic behavior.

Current Magnetic Field Changes:

Today, Earth’s magnetic field is still shifting. The magnetic north pole is moving at about 35 km per year—faster than in the past. However, this does not mean a reversal is near.

Conclusion:

Studying geomagnetic reversals and excursions helps scientists understand Earth’s internal processes and long-term changes. Projects like magnetic field sonification make these deep-time events easier to grasp. With continued research and modeling, we may better predict future changes in Earth’s magnetic behavior—and hear how they might sound.