Earth's Last Magnetic Field Reversal Took a Lot Longer Than Once Thought

New research on ancient lava flows has given us new longer estimates on the last magnetic-pole flip.
Chris Young

Every few hundred thousand years, the Earth's magnetic fields reverse - north becomes south and vice versa.

Scientists have long been researching the detectable flow of ancient lava in order to gain a better understanding of the mysterious phenomenon.

A team recently investigated these ancient lava flows, showing that Earth's last magnetic-pole flip likely took a lot longer than previously estimated.


The last reversal

The last magnetic pole reversal took place some 770,000 years ago.

As per, Scientists know the last pole reversal happened during the Stone Age. They have little knowledge about the duration of this event, including when the next flip is likely to occur.

Earth's magnetic field has flipped several times over the last 2.5 million years, with each flip usually occurring hundreds of thousands of years apart.

Earth's Last Magnetic Field Reversal Took a Lot Longer Than Once Thought
Study co-author Rob Coe and Trevor Duarte orienting cores from a lava flow site recording the Matuyama-Brunhes magnetic polarity reversal in Haleakala National Park, Hawaii, in 2015. Source: Brad Singer

Lava flow sequences

In the new study, the researchers used data on flow sequences of lava that erupted around the time of the last reversal to measure the duration of the event.

With this method, they estimated that the reversal occurred over the course of 22,000 years. This is much longer than previous estimates of 1,000 to 10,000 years. 

"We found that the last reversal was more complex, and initiated within the Earth's outer core earlier, than previously thought," lead study author Bradley Singer, a professor of geoscience at the University of Wisconsin-Madison, said to

In 1993, Singer was studying a volcano in Chile. While trying to date the lava, Singer realized that the lava had recorded strange, transitional magnetic-field directions in the lava-flow sequences. All of this, when compared to the date of the lava flows, revealed a history of the magnetic reversal process.

"Such records are indeed extremely rare, and I am one of [the] very few people who date them," Singer told 

Singer's life work is dedicated to better understanding the timing of magnetic-pole reversal.

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