Earth\u2019s magnetic field is generated by the churn of its liquid nickel-iron outer core, but it is not a constant feature.<\/p>\n
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\u2019t 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.<\/p>\n
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.<\/p>\n
Extended periods of reduced geomagnetic shielding likely influenced atmospheric chemistry, climate processes and the evolution of living organisms, according to co-author\u00a0Peter Lippert, an associate professor in the U Department of Geology & Geophysics.<\/p>\n
\u201cThe 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\u2019ll change organisms\u2019 ability to navigate,\u201d said Lippert, who heads the\u00a0Utah Paleomagnetic Center. \u201cIt\u2019s 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\u2019s logical to expect that there would be higher rates of genetic mutation. There could be atmospheric erosion.\u201d<\/p>\n
The results appear in\u00a0Nature Communications Earth & Environment. The lead author is\u00a0Yuhji Yamamoto\u00a0of Japan\u2019s Kochi University.<\/p>\n
\u201cThis finding unveiled an extraordinarily prolonged reversal process, challenging conventional understanding and leaving us genuinely astonished,\u201d Yamamoto wrote in a\u00a0summary posted by Springer Nature.<\/p>\n
Yamamoto and Lippert worked together on a 2012 drilling expedition in the North Atlantic that was investigating climate change during the Eocene Epoch, 56 to 34 million years ago. The two-month trip was facilitated by the\u00a0Integrated Ocean Drilling Program\u2019s\u00a0Expedition 342. The team drilled off the coast of Newfoundland in the North Atlantic, extracting sediment cores, layered time capsules built grain by grain over millions of years, from up to 300 meters below the sea floor.<\/p>\n
As paleomagnetists, Yamamoto and Lipperts\u2019 job was to \u201cmeasure the direction and the intensity of the magnetization that\u2019s preserved in those cores,\u201d Lippert said. \u201cWe don\u2019t know what triggers a reversal. Individual reversals don\u2019t last the same amount of time, so that creates this unique barcode. We can use the magnetic directions preserved in the sediments and correlate them to the geologic timescale.\u201d<\/p>\n
These sediments carry a reliable magnetic signal locked in by tiny crystals of magnetite produced by ancient microorganisms and from dust and erosion from the continents. Like a compass, the direction they point reveals Earth\u2019s polarity at the time the sediments were deposited.<\/p>\n
One 8-meter-thick layer took the scientists by surprise, appearing to record prolonged geomagnetic reversals in incredible detail.<\/p>\n
\u201cYuhji noticed, while looking at some of the data when he was on shift, this one part of the Eocene had really stable polarity in one direction and really stable polarity in another direction,\u201d Lippert said. \u201cBut the interval between them\u2014of unstable polarity when it went to the other direction\u2014was spread out over many, many centimeters.\u201d<\/p>\n
They realized this was no ordinary flip and collected extra samples at extremely fine spacing, just a few centimeters apart, to capture the sediments\u2019 story in high resolution.<\/p>\n
resolution and to test if the strange magnetic behavior was due to changes in the magnetic field or the sediments. In subsequent analysis of these cores over several years, Lippert and his colleagues confirmed this was recording changes in the magnetic field and constructed high-precision timelines for two reversals, one lasting 18,000 years and another for 70,000 years.<\/p>\n
While the finding was a surprise, it may not have been unexpected, according to the study. Computer models of Earth\u2019s geodynamo\u2014in the swirling outer core that generates the electrical currents supporting the magnetic field\u2014had indicated reversals\u2019 durations vary, with many short ones, but also occasional long, drawn-out transitions, some lasting up to 130,000 years.<\/p>\n
In other words, Earth\u2019s geomagnetism may have always had this unpredictable streak, but scientists hadn\u2019t caught it in the rocks until now.<\/p>\n","protected":false},"excerpt":{"rendered":"Earth\u2019s magnetic field is generated by the churn of its liquid nickel-iron outer core, but it is not…\n","protected":false},"author":2,"featured_media":458681,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[49,48,66],"class_list":["post-458680","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ca","tag-canada","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/458680","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=458680"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/458680\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/458681"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=458680"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=458680"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=458680"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}