Earth's magnetic field is generated by the churn of its liquid nickel-iron outer core, but it is not a constant feature.
Every so often, the magnetic north and south poles swap places in what are called geomagnetic reversals, and the record of these flips is preserved in rocks and sediments, including those from the ocean floor. These reversals don't happen suddenly, but over several thousand years, where the magnetic field fades and wobbles while the two poles wander and finally settle in the opposite positions of the globe.
Over the past 170 million years, the magnetic poles have reversed 540 times, with the reversal process typically taking around 10,000 years to complete each time, according to years of research. Now, a new study by a University of Utah geoscientist and colleagues from France and Japan has upended this scenario after documenting instances 40 million years ago where the process took far longer to complete, upwards of 70,000 years. These findings offer a new perspective on the geomagnetic phenomenon that envelops our planet and shields it from solar radiation and harmful particles from space.
Extended periods of reduced geomagnetic shielding likely influenced atmospheric chemistry, climate processes and the evolution of living organisms, according to co-author Peter Lippert, an associate professor in the U Department of Geology & Geophysics.
"The amazing thing about the magnetic field is that it provides the safety net against radiation from outer space, and that radiation is observed and hypothesized to do all sorts of things. If you are getting more solar radiation coming into the planet, it'll change organisms' ability to navigate," said Lippert, who heads the Utah Paleomagnetic Center. "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. There could be atmospheric erosion."
[...] "This finding unveiled an extraordinarily prolonged reversal process, challenging conventional understanding and leaving us genuinely astonished," Yamamoto wrote in a summary posted by Springer Nature.
[...] While the finding was a surprise, it may not have been unexpected, according to the study. Computer models of Earth's geodynamo—in the swirling outer core that generates the electrical currents supporting the magnetic field—had indicated reversals' durations vary, with many short ones, but also occasional long, drawn-out transitions, some lasting up to 130,000 years.
In other words, Earth's geomagnetism may have always had this unpredictable streak, but scientists hadn't caught it in the rocks until now.
Journal Reference: Yamamoto, Y., Boulila, S., Takahashi, F. et al. Extraordinarily long duration of Eocene geomagnetic polarity reversals. Commun Earth Environ 7, 180 (2026). https://doi.org/10.1038/s43247-026-03205-8
(Score: 1) by khallow on Tuesday April 07, @04:44PM
Even at "typical" times, that means at least 5.4 million years has been spent in periods of a flip transition. So 3% of the past 170 million years. If the atmospheric erosion is much higher at these times, then these might be significant contributors to loss of atmosphere.
(Score: 3, Interesting) by VLM on Wednesday April 08, @06:09PM
How do they know? They don't.
I looked into this and the shortest time period data is some pretty questionable freezing lava flow data that might have once indicated variations of up to 3 degrees per day or who knows.
For short term stuff during boring times, like now, the field can vary quite a bit down to almost audio range. Being something big it can't vary too fast without speed of light / speed of sound type concerns so that sets a max frequency change limit.
We don't have any data more detailed than "a day, or more likely, some days" for historical data. It could oscillate at 60 Hz for all we know.
I bring this up because moving fields, even weak ones, if they're huge enough volume, induce currents in conductors, even crappy conductors like rocks. So that SEEMS to set a max rate of change over the short term or you'd have weird stuff like semi-conductive coal beds heating themselves until they turn themselves into natgas instead of coal, or seams of metal ore melting themselves, which doesn't seem to happen (much).
If you're into ham radio stuff, being a shortwave ham radio guy during a geomagnetic reversal is extremely unlikely to happen in our lifetimes but it would be pretty exciting, I think. Or if you want to think about it from a hard sci fi perspective a civilization living thru a reversal MIGHT be able to do "Tesla free energy stuff" like just wave a coil in the air to get near infinite free electicity. Strange to think about. Imagine a planet where you can't ship "long coils of copper wire" because they might catch fire due to crazy geomagnetic storms, maybe. Maybe they'd ship all cables in mu-metal magent proof boxes LOL instead of Amazon cardboard shipping boxes.