Other planets on the Milky Way could have oceans and continents like Earth

This latest major geomagnetic turnaround has triggered a series of dramatic events that have far-reaching consequences for our planet. They read like the action of a horror movie: the ozone layer was destroyed, electric storms raged through the tropics, solar winds generated spectacular light emissions (auroras), arctic air spilled over North America, ice sheets and glaciers and weather patterns shifted sharply.

During these events, life on Earth was exposed to intense ultraviolet light, Neanderthals and giant animals known as megafauna became extinct, while modern humans sought protection in caves.

The magnetic north pole – where the compass needle points – has no permanent place. Instead, it usually revolves around the geographic north pole – the point around which the Earth revolves – over time due to movement within the Earth’s core.

For reasons that are still not clear enough, the movements of the magnetic poles can sometimes be more extreme than fluctuations. One of the most dramatic of these sex migrations occurred some 42,000 years ago and is known as the Laschamps Excursion – named after the village where it was discovered in France’s Central Massif.

Laschamps ’field trip has been recognized around the world, including recently in Tasmania, Australia. But so far it has not been clear whether such magnetic changes have had an impact on climate and life on the planet. Our new work brings together multiple lines of evidence that strongly suggest that the effects were indeed global and far-reaching.

Ancient trees

To investigate what happened, we analyzed ancient New Zealand cowrie trees that have been preserved in peat bogs and other sediments for more than 40,000 years. Using annual growth rings on cowrie trees, we were able to create a detailed time frame of how the Earth’s atmosphere changed during this time. The trees revealed a prolonged jump in atmospheric radiocarbon levels caused by the collapse of the Earth’s magnetic field during the pole shift, providing a way to precisely connect widely geographically dispersed records.

“The cowrie trees are like rosette stones, helping us connect records of environmental changes in caves, ice cores and peatlands around the world,” said Professor Alan Cooper, who co-led the research project.

Using the newly created time frame, we were able to show that the tropical Pacific rainforests and westerly winds of the Southern Ocean shifted abruptly at the same time, bringing arid conditions to places like Australia simultaneously with a range of megafauna, including giant kangaroos and giant wombats became extinct. Further north, the vast Laurentide ice sheet grew rapidly throughout the eastern United States and Canada, while in Europe the Neanderthals spirally became extinct.

Climate modeling

Working with a computer program that simulated global interactions between chemistry and climate, we investigated the impact of a weaker magnetic field and changes in the Sun’s power. Importantly, during the magnetic switch, the strength of the magnetic field dropped to less than 6% of what it is today. The compass of the time would struggle even to find the north.

An ancient cow cow from Ngāwhā in New Zealand. Nelson Parker, author

Since there is basically no magnetic field, our planet has completely lost its very effective shield from cosmic radiation, and many other of these very penetrating particles from space could access the top of the atmosphere. On top of all that, the Sun experienced several “large solar minima” during this period, during which total solar activity was generally much lower but also more unstable, emitting numerous massive solar flares that allowed stronger ionizing cosmic rays to reach Earth.

Our models showed that this combination of factors amplified. High-energy cosmic rays from the galaxy, as well as huge bursts of cosmic rays from solar flares, could penetrate the upper atmosphere, filling particles in the air and causing chemical changes that led to the loss of stratospheric ozone.

The modeled simulations of chemistry and climate are in line with the changes in the environment observed in many archives of the natural climate and environmental changes. These conditions would also extend the bright aurora light emissions around the world – sometimes the nights would be as bright as day. We suggest that dramatic changes and unprecedented high levels of UV led to early humans seeking refuge in caves, explaining the apparent sudden boom in cave art around the world 42,000 years ago.

It must have seemed like days.

Adams event

Because of the coincidence of seemingly random cosmic events and extreme changes in the environment recorded around the world 42,000 years ago, we called this period the “Adams event” – a tribute to the great science fiction writer Douglas Adams, who wrote the Hitchhiker’s Guide to the Galaxy and identified “42” as the answer to life, the universe and all.Douglas Adams was really into something big, and the remaining mystery is how did he know?

Chris Fogwill is Professor of Glaciology and Paleoclimatology and Head of School Geography, Geology and Environment and Director of the Institute for a Sustainable Future at Keele University.

Alan Hogg is a professor and director of the Carbon Delivery Laboratory at Waikato University.

Chris Turney is Professor of Earth Sciences and Climate Change, Director of the Center for Earth Science and Sustainability, Director of the Chronos 14Carbon-Cycle Facility and UNSW Director of the ARC Center for Excellence in Australian Biodiversity and Heritage, UNSW.

Zoë Thomas is an ARC DECRA colleague, UNSW.

Disclosure Statements: Chris Fogwill receives funding from UKRI and the Australian Research Council. Many thanks to Professor Alan Cooper, Honorary Researcher of the South Australian Museum, who co-led this study, Associate Professor Ken McCracken, and others. Jonathan Palmer of the University of New South Wales, Drew Lorrey of the National Water Institute of New Zealand and Atmospheric Research, Ph.D. Janet Willmshurst of Landcare Research and our co-authors on a published article.

Professor Alan Hogg works at Waikato University in Hamilton, New Zealand. He is a research associate in the Royal Society of New Zealand Marsden grant – MFP-NIW1803: dr. Andrew Lorrey, NIWA, Auckland, Chief Investigator.

Chris Turney receives funding from the Australian Research Council and is a scientific advisor to the graffiti cleaning company CarbonScape (https://www.carbonscape.com).

Zoë Thomas receives funding from the Australian Research Council.

Published with permission to talk.

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