A reversal in Earth’s magnetic field hundreds of years in the past plunged the planet into an environmental disaster that will have resembled “a disaster movie,” scientists not too long ago found.
Our planet‘s magnetic field is dynamic and, quite a few occasions, it has flipped — when the magnetic North and South Poles swap locations. In our electronics-dependent world, such a reversal may significantly disrupt communication networks.
But the affect could possibly be much more severe than that, in response to the brand new research. For the primary time, scientists have discovered proof that a polar flip may have severe ecological repercussions. Their investigation connects a magnetic field reversal about 42,000 years in the past to climate upheaval on a international scale, which induced extinctions and reshaped human habits.
Related: What if Earth’s magnetic field disappeared?
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Earth’s magnetosphere — the magnetic barrier surrounding the planet — originates from the churning of scorching, molten metallic round its iron core. This perpetually sloshing liquid circulate generates electrical energy that in flip produces magnetic field traces, which curve across the planet from pole to pole, in response to NASA.
Like a protecting bubble, the magnetic field shields Earth from photo voltaic radiation. On the planet’s sun-facing aspect, fixed bombardment from photo voltaic winds squishes the magnetic field, in order that the field extends to a distance not more than 10 occasions Earth’s radius. However, on the aspect of the planet dealing with away from the solar, the field extends a lot farther into house, forming an infinite “magnetotail” that reaches past our moon, NASA says.
Marking the 2 spots on Earth the place arcing magnetic field traces converge are the magnetic North Pole and South Pole. But whereas these positions are comparatively secure, the poles — and the magnetic field itself — aren’t fastened in place. About as soon as each 200,000 to 300,000 years, the field weakens sufficient to reverse polarity fully. The course of can take a whole lot and even hundreds of years, in response to NASA.
Magnetic molecules preserved in volcanic deposits and different sediments inform scientists when previous reversals occurred; these molecules align with the magnetic field on the time that they have been deposited, so that they point out the situation of the magnetic North Pole, mentioned lead research creator Alan Cooper, an emeritus professor within the Department of Geology on the University of Otago in New Zealand.
Recently, researchers questioned whether or not a comparatively current and temporary polarity reversal referred to as the Laschamps Excursion, which occurred between 41,000 and 42,000 years in the past, could possibly be linked to different dramatic modifications on Earth from that point, which had not beforehand been attributed to exercise within the magnetosphere. They suspected that in a time when our protecting magnetic field was reversing — and thereby weaker than regular — photo voltaic and cosmic radiation publicity may have an effect on the ambiance sufficient to affect climate, the research authors reported.
Clues in “biscuits”
Prior research of Greenland ice cores relationship to Laschamps did not reveal proof of climate change, in response to the research. But this time, the researchers turned their consideration to a different potential supply of climate knowledge: bog-preserved kauri bushes (Agathis australis) from northern New Zealand.
They lower cross-sections, or “biscuits,” from the preserved trunks, and checked out modifications in ranges of carbon 14, a radioactive type of the ingredient, over a interval that included the Laschamps reversal. Their evaluation revealed elevated ranges of radioactive carbon within the ambiance throughout Laschamps, when the magnetic field was weakening.
“Once we worked out the exact timing from the kauri record, we could see that it coincided perfectly with records of climatic and biological change all over the world,” Cooper advised Live Science in an e mail. For instance, round this time, megafauna in Australia started to go extinct and Neanderthals in Europe have been dying out; their decline could have been accelerated by climate-related modifications to their ecosystems, Cooper mentioned.
The authors then used pc climate fashions to check what could have induced widespread climate upheaval and associated extinctions. They discovered that a weak magnetic field — working at about 6% of its regular power — may result in main climate impacts “via the ionizing radiation strongly damaging the ozone layer, letting in UV [ultraviolet rays] and altering the ways in which the sun’s energy was absorbed by the atmosphere,” Cooper defined.
A closely ionized ambiance may even have generated sensible auroras world wide and produced frequent lightning storms, making skies appear to be “something similar to a disaster movie,” Cooper mentioned.
Another vital shift round that point was in Homo sapiens, with cave artwork starting to seem in areas world wide. This included the primary examples of pink ochre hand stencils, “which we suspect is actually a sign of the application of sunscreen,” a apply nonetheless seen in trendy Indigenous teams in Namibia, Cooper mentioned. Higher UV ranges from a weak magnetic field may have pushed people to hunt shelter in caves, or compelled them to guard their pores and skin with sunblocking minerals, he mentioned.
Scientists cannot predict exactly when the following reversal of our magnetic field may occur. However, some indicators — such because the North Pole’s present migration throughout the Bering Sea space and the magnetic field itself weakening almost 10% over the previous 170 years — recommend that a flip could also be nearer than we predict, making it extra pressing that researchers absolutely perceive how massive shifts in our magnetic field may form environmental modifications on a international scale, in response to the research.
“Overall, these findings raise important questions about the evolutionary impacts of geomagnetic reversals and excursions throughout the deeper geological record,” the scientists wrote.
The findings have been printed on-line Feb. 18 within the journal Science.
Originally printed on Live Science.