bbc Earth's magnetic field now shifts more than ever "Because of changing temperatures and fluid flows, the strength of the magnetic field varies, and the positions of the north and south magnetic poles shift. These shifts leave traces in rocks. When lava cools, metal oxide particles within the rock become frozen in the direction of the prevailing magnetic field. So scientists can work out the historic positions of the magnetic poles by examining and dating lava samples. As a result we know there have been about 170 magnetic pole reversals during the last 100 million years, and that the last major reversal was 781,000 years ago." cbc When north goes south Nature of things with David Suzuki explaining polar reversals and the effect on climate. (Canada only, others use this YouTube Link) earthsky Earth’s last magnetic reversal took less than 100 years Paul Renne, director of the Berkeley Geochronology Center and a University of California Berkeley professor-in-residence of Earth and planetary science is a coauthor of the study. He said: We should be thinking more about what the biologic effects would be. extremetech Earth’s magnetic field could flip within our lifetime "Now, however, a new study has analyzed rocks from the previous flip — the Matuyama-Brunhes magnetic reversal of 786,000 years ago — and found that the process completed in under 100 years." [doi: 10.1093/gji/ggu287] geomag Is there any danger to life? "Almost certainly not."

japan Scientists in Japan Just Found a Detailed Record of Earth's Last Magnetic Switcharoo This new study is titled "A full sequence of the Matuyama–Brunhes geomagnetic reversal in the Chiba composite section, Central Japan." The lead author is Yuki Haneda, a project researcher at the National Institute of Polar Research and a postdoctoral research fellow at the National Institute of Advanced Industrial Science and Technology in Japan. What they found goes against what some other studies have uncovered, especially when it comes to how long the reversal took to occur. Some studies suggest it took several thousand years, while another suggested that the reversal was completed in one human lifetime. The different time estimates depend largely on where on Earth researchers gather their evidence. This study based on the Chiba composite section says it took about 20,000 years, including a 10,000 year period of instability leading up to the reversal. nasa Magnetic Pole Reversal Happens All The (Geologic) Time "It is moving faster now, actually, as scientists estimate the pole is migrating northward about 40 miles per year, as opposed to about 10 miles per year in the early 20th century." physorg Poles flip completely "Geophysicists have been studying the lava that has seeped up from the core and through a ridge on the floor of the Atlantic Ocean. As lava cools and solidifies, it preserves the direction of the Earth’s magnetic field so looking at the rock that has formed over time gives us an idea of what has happened to the magnetic poles in the past. These studies show that the poles switch ends every half million years or so – and that we’re due for another switch in the next few thousand years. There’s also evidence to suggest that before the Earth’s magnetic poles switch, the magnetic field slowly fades out before reappearing with the poles reversed. And our magnetic field has depleted by 5% over the last century." smithsonian What Will Happen When the Earth’s Magnetic Field Begins to Reverse? "With the sphere spinning at 45 miles per hour, and a little help from electro­magnets, the team saw short-lived magnetic bursts within the sodium. When the spinning ramps up to nearly 90 miles per hour later this year, the sodium might generate a field without the extra nudge. If so, and with one second of the experiment equaling 5,000 years of Earth time, the researchers could see a reversal before everyone else on the planet."