A global period of revolt 42,000 years ago was the result of a reversal of the Earth’s magnetic field, new research has found.
According to the radiocarbon preserved in the rings of ancient trees, a breakdown of the climate for centuries, mass disappearances and even changes in human behavior can be directly related to the last time the Earth’s magnetic field changed its polarity.
The research team named the period the “Adams Transition Geomagnetic Event” or the “Adams Event,” after scientific writer Douglas Adams, who famously declared the 42nd supreme answer to life, the universe, and everything else.
“For the first time, we were able to accurately date the time and environmental impact of the latest magnetic pole switch,” said Earth scientist Chris Turney of the University of New South Wales in Australia.
“The discoveries were made possible by ancient New Zealand kauri trees, which have been preserved in sediments for over 40,000 years. Using ancient trees we were able to measure and date the increase in atmospheric radiocarbon levels caused by the collapse of the Earth’s magnetic field. “
The most recent period of magnetic reversal is known as the Laschamp event and is what we call a geomagnetic trip. This is when the planet’s magnetic poles briefly change places before returning to their original positions. It is one of the best studied events of the Earth’s magnetic field, recorded by ferromagnetic minerals.
It took place about 41,000 years ago and lasted about 800 years. However, it was not clear what impact this event had on life on the planet – so when scientists discovered an ancient kauri tree (Agathis australis) in 2019, which was alive in this time period, took the opportunity to learn more.
This is because trees record atmospheric activity in their annual growth rings. In particular, carbon 14 or radiocarbon can reveal a lot of information about celestial activity.
Radiocarbon only appears on Earth in traces, compared to other natural carbon isotopes. It forms in the upper atmosphere under the bombardment of cosmic rays from space. When these rays enter the atmosphere, they interact with local nitrogen atoms to trigger a nuclear reaction that produces radiocarbon.
Because cosmic rays flow constantly in space, the Earth receives a more or less constant amount of radiocarbon. Therefore, an increase in radiocarbon in tree rings tells us that the Earth had a higher exposure to radiocarbon during that year.
When the Earth’s magnetic field is weakened, as it was during the Laschamp event, more cosmic rays enter the atmosphere to produce more radiocarbon. Because of this, scientists have been able to find out earlier that the Earth’s magnetic field has weakened to about 28% of its normal power in that 800-year period.
The kauri tree, however, allowed the research team to study the years leading up to the Laschamp event. They found that the Adams event occurred about 42,200 years ago, and the magnetic field was at its weakest point. before the Laschamp event.
“The Earth’s magnetic field dropped to just 0-6 percent during the Adams event,” Turney said. “In essence, we had no magnetic field at all – our shield of cosmic radiation was completely gone.”
During this time, the Sun’s magnetic field would also have weakened several times, as it also experienced magnetic reversal as part of its regular cycle. These periods see less solar activity and flare, but the Sun’s magnetic field provides the Earth with a measure of protection against cosmic rays – so during these solar minimums, the bombardment of cosmic rays would have increased again.
This weakened magnetic field would have triggered substantial changes in the Earth’s atmospheric ozone, with dramatic consequences, including thunderstorms and spectacular auroras and climate change around the world.
“Unfiltered radiation from space shattered air particles in the Earth’s atmosphere, separating electrons and emitting light – a process called ionization,” Turney said.
“Ionized air has ‘fried’ the ozone layer, triggering a wave of climate change around the globe.”
This is in line with the current climate and environmental changes seen in other records around the globe, such as the mysterious disappearance of megafauna in Australia.
Curiously, it also coincides with some of the oldest rock art we have recorded, leading researchers to hypothesize that the Adams event may have led people inside.
“This sudden change in behavior in different parts of the world is consistent with an increasing or altered use of caves during the Adams event, potentially as a shelter against the growth of B ultraviolet, potentially at harmful levels, during minimums or solar energy particles, which could also explain an increased use of red ocher sunscreen, “they wrote in their paper.
This is somewhat speculative, of course, but it suggests that a geomagnetic reversal may be a world-changing event. And recent evidence has suggested that we are now one step ahead.
This, the researchers say, could be absolutely disastrous in today’s climate.
“Our atmosphere is already full of carbon at levels never seen before by humanity. A reversal of the magnetic pole or an extreme change in the Sun’s activity would be unprecedented accelerators of climate change,” Turney said.
“We urgently need to reduce carbon emissions before such a random event happens again.”
The research was published in Science.