Earth saw a lot of commotion when its magnetic poles flipped 42,000 years ago.
Scientists have known about the flip since the late 1960s. Earth’s magnetic poles aren’t static — they’re generated by electric currents from the planet’s liquid outer core, which is constantly in motion. As of late, Earth’s magnetic North pole has wandered considerably on a path toward northern Russia.
But for the most part, scientists didn’t think the last pole flip had a major environmental impact. Sure, the planet’s magnetic field got weaker, allowing more cosmic rays to penetrate the atmosphere, but plant and animal life wasn’t known to have been greatly affected.
A new study now suggests a more dramatic phenomenon occurred: The additional cosmic rays may have depleted ozone concentrations, opening the floodgates for more ultraviolet radiation in the atmosphere.