Scientists claim: Earth's magnetic field reversal lasts longer than expected

A recent study published in Communications Earth & Environment suggests that Earth’s magnetic field reversals may last far longer than previously assumed.

Earth’s Magnetic Field and Geomagnetic Reversals

¨   Earth’s magnetic field helps in navigation and forms the magnetosphere, protecting the planet from harmful solar wind and cosmic radiation.

¨     The field is generated through the geodynamo process, caused by the movement of molten iron and nickel in Earth’s outer core (~2,200 km thick).

¨     Over geological time, the magnetic north and south poles periodically reverse, a phenomenon known as geomagnetic reversal.

¨     Evidence of past reversals is preserved in rocks and marine sediments, where magnetic minerals (such as magnetite crystals) align with the Earth’s magnetic field when deposited.

¨     Scientists estimate that around 540 geomagnetic reversals have occurred over the past 170 million years.

¨     Earlier studies suggested that reversals generally occur over 2,000–12,000 years, with about 10,000 years considered the typical duration.

Findings of the New Study

¨     An international team of researchers from Japan, France, and the United States, led by Yuhji Yamamoto (Kochi University) and Peter Lippert (University of Utah), analyzed deep-sea sediment cores from the North Atlantic near Newfoundland, Canada.

¨  These sediments were collected during the Integrated Ocean Drilling Program expedition (2012).

The researchers examined sediment layers from the Eocene epoch (~40 million years ago) using

¨     X-ray scanning

¨     Magnetic measurements

¨     Astronomical tuning of sediment layers

Their analysis identified two unusually long geomagnetic reversals

¨     One lasting about 18,000 years

¨     Another lasting around 70,000 years

The longer reversal showed complex behaviour, including precursor phases and multiple rebounds, where the magnetic field temporarily shifted direction before stabilizing.Numerical simulations of the Earth’s core suggested such long reversals are rare but natural outcomes of geodynamo dynamics, potentially lasting up to 130,000 years.

Implications for Earth and Future Research

¨     During geomagnetic reversals, the magnetic field weakens significantly, reducing Earth’s protection from solar and cosmic radiation.

Prolonged reversals could therefore lead to

¨     Higher radiation exposure

¨     Increased genetic mutations

¨     Possible atmospheric erosion

Disruption of animal navigation, since many species rely on Earth’s magnetic field.

Such conditions may have influenced ancient ecosystems and evolutionary processes.The Eocene period, when these long reversals occurred, also had higher global temperatures and CO₂ levels, making it a useful climate analogue for future warming scenarios.Scientists note that Earth’s magnetic field strength has declined by about 5% per century in recent measurements, while the magnetic North Pole continues to drift toward Siberia, raising questions about whether a future reversal could eventually occur.Future research will analyze lava sequences in Iceland and geomagnetic excursions preserved in sediment records better to understand the causes and duration of magnetic reversals.