This recent massive geomagnetic revolution brought a series of dramatic events that have a profound impact on our planet. They read like a plot of a horror movie: the ozone layer was destroyed, electric storms swept over the tropics, solar winds generated spectacular light displays (auroras), Arctic air was poured all over America that -North, ice sheets and glaciers moved and weather patterns violently shifted. .
During these events, life on Earth was exposed to intense ultraviolet light, Neanderthals and large animals called megafauna became extinct, while modern humans sought refuge in caves.
The magnetic north pole has no permanent location – where a compass needle points. Instead, it usually moves around near the geographic north pole – the point around which the Earth spins – over time due to movements within the Earth’s core.
For reasons that are not yet entirely clear, magnetic pole movements can be beyond wobble. One of these most impressive pole vaults took place about 42,000 years ago and is known as Laschamps Excursion – named after the town where it was discovered in the French Massif Center.
The Laschamps Tour has been recognized around the world, most recently in Tasmania, Australia. But so far, it was not clear whether such changes had any impact on climate and life on the planet. Our new work brings together a number of lines of evidence that strongly suggest that the impacts were indeed global and far-reaching.
Ancient trees
To investigate what happened, we analyzed ancient New Zealand kauri trees that have been preserved in peat bogs and other sediments for over 40,000 years. Using the annual growth rings in the kauri trees, we are able to create a detailed timeline of how the Earth’s atmosphere has changed over this period. The long spike trees appeared in atmospheric radiocarbon levels caused by the collapse of the Earth’s magnetic field when the poles turned, providing a way to connect plates that were scattered across the country.
“The kauri trees resemble the Rosetta Stone, helping us link records of environmental change in caves, ice cores, and swamps around the world,” said Professor Alan Cooper, who co-directed the project this research.
Using the newly created time frame, we were able to show that the tropical waters of the Pacific Ocean and the westerly winds of the South Atlantic moved abruptly at the same time, giving wet conditions to places like Australia at the same time as a range of megafauna, including large kangaroos. and great onions became extinct. Further north, the great Laurentide Ice Sheet grew rapidly throughout the eastern U.S. and Canada, and in Europe the Neanderthals became extinct.
Climate modeling
Working with a computer program that resembled a global interaction between chemistry and climate, we studied the effects of a weaker magnetic field and changes in the strength of the sun. Importantly, during the magnetic conversion, the strength of the magnetic field dropped to less than 6% of what it is today. A compass back then would be hard to find even to the north.
Log of an old kauri tree from Ngāwhā, New Zealand. Nelson Parker, author donated
With no real magnetic field, our planet lost its very effective shield against cosmic radiation, and many more of these terrifying grains would travel from space to the top of the atmosphere. In addition, the Sun experienced a number of “grand solar minima” during this period, when solar activity was generally much lower but also more volatile, emitting several solar flames that allowed more powerful ionizing cosmic rays to reach the Earth.
Our models showed that this combination of factors had an amplifying effect. The high-energy cosmic rays from the galaxy and also large explosions of cosmic rays from solar flames were able to enter the upper atmosphere, shattering the particles in the air and causing chemical changes that removed stratospheric ozone.
The modeled climate-chemistry simulations are consistent with the environmental trends seen in many natural and environmental climate change archives. These conditions would also have amplified the brilliant light displays of the aurora around the world – at times, nights would have been as bright as daylight. We applaud the incredible changes and unprecedented high levels of UV that led early humans to find shelter in caves, explaining the sudden appearance of cave art around the world. 42,000 years ago.
It must have been like the end of days.
Adams event
Because of the coincidence of random cosmic events and the great environmental changes that were discovered around the world 42,000 years ago, we have dubbed this time the “Adams Event” – a tribute to the great science fiction writer. Douglas Adams, who wrote The Hitchhiker’s Guide to the Galaxy and marked “42” as the answer to life, the universe and everything. Douglas Adams was really into something big, and is the mystery left as he knew it?
Chris Fogwill is a professor of geology and palaeoclimatology, and head of school geography, geology and the environment and director of the Institute for Sustainable Future, Keele University.
Alan Hogg is a professor and director of the Carbon Dating Laboratory, University of Waikato.
Chris Turney is professor of earth science and climate change, director of the Earth Science and Sustainability Research Center, director of the 14Carbon-Cycle Chronos Facility, and UNSW director of the ARC Center of Excellence in Australian Biodiversity and Heritage, UNSW.
Zoë Thomas is a member of ARC DECRA, UNSW.
Publication statements: Chris Fogwill receives funding from UKRI and the Australian Research Council. Many thanks to Professor Alan Cooper, an honorary researcher at the Museum of South Australia, who co-directed this study, Professor Ken McCracken and Dr Jonathan Palmer at the University of New South Wales, Drew Lorrey at the National Institute of New Zealand Water and Atmospheric Research, Dr. Janet Willmshurst at Landcare Research and our co-authors of the published article.
Professor Alan Hogg works at the University of Waikato in Hamilton, New Zealand. He is an associate researcher in the Marsden donation from the Royal Society of New Zealand – MFP-NIW1803: Dr. Andrew Lorrey, NIWA, Auckland, principal investigator.
Chris Turney is funded by the Australian Research Council and is a scientific advisor to clean up the graphite company CarbonScape (https://www.carbonscape.com).
Zoë Thomas is funded by the Australian Research Council.
Posted with permission from the Conversation.
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