Earth's magnetic field reversed extremely rapidly soon after modern humans first arrived in Europe, completely flip-flopping in less than a thousand years.
Earth's magnetic field reversed extremely rapidly soon after modern humans first arrived in Europe, completely flip-flopping in less than a thousand years, new research suggests.
These findings, detailed Oct. 15 in the journal Earth and Planetary Science Letters, could shed light on how and why magnetic field reversals happen, and how they leave Earth vulnerable to solar and space radiation, the study scientists said.
Earth's metal core acts like a giant magnet that emanates a magnetic field with two poles, north and south. These two magnetic poles very roughly match where the planet's geographic north and south poles lie, which mark the axis on which Earth spins.
"The Earth's magnetic field is a highly dynamic feature," said researcher Norbert Nowaczyk, a paleomagnetist at the GFZ German Research Centre for Geosciences. "Its intensity pulsates between values 50 percent higher than today, or 90 to 95 percent lower than today."
In addition, every several hundred thousand years, Earth's magnetic field reverses — a compass that would have pointed north would instead aim south. These flips are captured by magnetically sensitive minerals in cooling lava that are literally set in stone pointing to where the poles were at that particular moment in Earth's history. (Earth Quiz: Mysteries of the Blue Marble)
Full reversals of the magnetic field usually take millennia to finish, based on those frozen rock records. However, scientists now find that 41,000 years ago, shortly after modern humans first entered Europe, the magnetic poles flipped and flipped again in less than a millennium.
Scientists analyzed data in sediment from the floor of the Black Sea and compared it with other data from the North Atlantic, the Southeast Pacific and around Hawaii. Surprisingly, they found the Earth's magnetic field took about 200 years to flip, during which time it was just one-twentieth as strong as it is today.
"Former ideas about a field reversal deal with durations of 2,000 to 5,000 years," Nowaczyk told OurAmazingPlanet.
Earth's magnetic field stayed reversed for only 440 years, during which time it was just one-quarter as strong as it is today. The magnetic poles then flipped back to approximately where they were before over the course of about 270 years. The flip-flop overall is known as the Laschamp event, after the area in France where evidence of it was first discoveredin the 1960s. These new findings reveal how quick this reversal was.