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Prolonged Geomagnetic Reversals Challenge Scientific Understanding

February 5, 2026

Earth’s magnetic field, the invisible shield that protects our biosphere from deadly cosmic radiation, operates according to patterns that scientists are only beginning to fully comprehend. New research published in Communications Earth & Environment has overturned long-held assumptions about the duration of geomagnetic reversals, documenting instances 40 million years ago where the pole-switching process took up to seven times longer than previously estimated.

The Mechanics of Earth’s Magnetic Shield

Earth’s magnetic field originates from the geodynamo—the complex system of convection currents in the planet’s liquid nickel-iron outer core. As this molten metal churns beneath the solid mantle, it generates the electrical currents responsible for our planet’s magnetism. This field extends far into space, creating the magnetosphere that deflects the constant stream of charged particles emanating from the sun.

Throughout geological history, the magnetic poles have periodically reversed their polarity. The geological record, preserved in volcanic rocks and ocean sediments, indicates that these reversals have occurred approximately 540 times over the past 170 million years. The prevailing scientific consensus held that each reversal typically required around 10,000 years to complete.

A Paradigm-Shifting Discovery

This assumption has been fundamentally challenged by an international research team comprising scientists from the University of Utah, France, and Japan. Their investigation centered on sediment cores extracted during a 2012 drilling expedition in the North Atlantic Ocean, off the coast of Newfoundland.

The researchers, including paleomagnetists Peter Lippert and Yuhji Yamamoto, extracted layered sediment cores from depths of up to 300 meters below the seafloor. These sediments function as geological archives, with microscopic magnetite crystals—produced by ancient microorganisms and continental erosion—recording the magnetic field orientation at the time of deposition.

Within an 8-meter-thick sediment layer corresponding to the Eocene Epoch (56-34 million years ago), the team identified an anomalous section displaying prolonged magnetic instability. Subsequent high-resolution sampling, conducted at intervals of just a few centimeters, enabled the reconstruction of two remarkably extended reversals: one lasting 18,000 years and another spanning an extraordinary 70,000 years.

Implications for Earth’s Biosphere

The extended duration of these reversals carries profound implications for life on Earth. During the reversal process, the magnetic field weakens substantially, diminishing the planet’s protection against harmful cosmic radiation.

“The amazing thing about the magnetic field is that it provides the safety net against radiation from outer space,” explained Professor Lippert, who directs the Utah Paleomagnetic Center. “If you are getting more solar radiation coming into the planet, it’ll change organisms’ ability to navigate. It’s basically saying we are exposing higher latitudes in particular, but also the entire planet, to greater rates and greater durations of this cosmic radiation, and therefore it’s logical to expect that there would be higher rates of genetic mutation.”

Lippert also noted the possibility of atmospheric erosion during extended periods of weakened magnetic shielding—a phenomenon that scientists believe may have contributed to Mars losing its atmosphere billions of years ago.

Computer Models Predicted This

Interestingly, computer simulations of Earth’s geodynamo had previously suggested that reversal durations might vary considerably, with some transitions potentially lasting up to 130,000 years. Until now, however, direct geological evidence supporting these predictions had remained elusive.

The research team’s findings, which Yamamoto described as “genuinely astonishing,” represent the first observational confirmation of these extended-duration events in the geological record.

Vocabulary Help

• geodynamo — the mechanism in Earth’s core that generates the magnetic field through convection currents
• paleomagnetist — a scientist who studies ancient magnetic fields recorded in rocks
• anomalous — deviating from what is standard, normal, or expected
• paradigm — a model or pattern of thinking; a typical example
• convection — the movement of heat through liquids or gases

Grammar Focus

• Complex noun phrases: “the constant stream of charged particles emanating from the sun”
• Reduced relative clauses: “sediments…corresponding to the Eocene Epoch”
• Passive constructions for scientific writing: “This assumption has been fundamentally challenged…”

Source: Phys.org