It seems a huge fossilized tree in New Zealand has got the scientific world all abuzz.
A perfectly preserved ancient tree fossil has offered scientists a unique peek into a moment 42,000 years ago when the Earth’s magnetic field went haywire. The impressive study paints a picture of temporary environmental chaos, potentially influencing everything from an increase in cave paintings to the extinction of the Neanderthals.
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Geomagnetic excursions are short-lived, and involve temporary changes to the Earth’s magnetic field lasting anywhere from a few hundred to a few thousand years. The most recent recorded geomagnetic excursion is known as the Laschamps excursion and it took place around 42,000 years ago.
"The Laschamps Excursion was the last time the magnetic poles flipped," explains Chris Turney, co-lead author on a landmark new study investigating this transformative event. "They swapped places for about 800 years before changing their minds and swapping back again."
Scientists have known about these dramatic magnetic pole events for a long time but it’s never been clearly understood what kind of impact they have on life or the environment. That is until a few years ago, when an ancient fossilized tree was discovered in New Zealand.
Workers preparing a site for a new power-plant unearthed the massive kauri tree trunk, perfectly preserved for 42,000 years, with its rings offering up an incredible 1,700-year record of the Earth’s environmental conditions exactly spanning the period of the Laschamps Excursion.
"For the first time ever, we have been able to precisely date the timing and environmental impacts of the last magnetic pole switch," says Turney. "Using the ancient trees we could measure, and date, the spike in atmospheric radiocarbon levels caused by the collapse of Earth's magnetic field."
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The results reveal an incredibly dramatic period of environmental change, particularly in the stretch of time leading up to the few hundred years the Earth’s magnetic field was reversed. The study calculated a depleted ozone layer, higher levels of ultraviolet radiation and increased atmospheric ionization all coalesced about 42,000 years ago. In tribute to author Douglas Adams – in whose book The Hitchhiker's Guide the the Galaxy, the supercomputer Deep Thought calculates the answer to the ultimate question of life, the universe and everything is "42" – the researchers named this specific period the “Adams Transitional Geomagnetic Event.”
"The more we looked at the data, the more everything pointed to 42," says Turney. "It was uncanny.”
Alan Cooper, co-lead author on the study, suggests a number of novel environmental conditions would have appeared during the so-called Adams Event. Auroras, for example, would have been widespread across the entire planet, alongside extraordinary volumes of electrical storms due to increases in ionized air.
“Early humans around the world would have seen amazing auroras, shimmering veils and sheets across the sky,” says Cooper. “It must have seemed like the end of days.”
There's more at the link.
I can't help wondering how prehistoric humans - if they were actually human by that stage; opinions differ - would have experienced that. Without any scientific framework to speak of, everything would have been explained through superstition and mythology. How many ancient pantheons had their genesis in the weird play of light across the night sky during the Laschamps Excursion? We'll probably never know . . .
This is the kind of discovery that a young scientist, having just completed his doctorate, can start work on as a researcher, and retire forty or fifty years later without having finished his work. It's going to keep them busy for decades.