A time of global upheaval 42,000 years ago led to a reversal of the Earth’s magnetic field, a new study has found.
According to radiocarbon preserved in ancient tree rings, the value of several centuries of climate breakdown, extinction, and even changes in human behavior can be directly related to the last time it changed. Earth’s magnetic range to polarity.
The research team has named the time as the Adams Interim Geomagnetic Event, or Adams Event, after sci-fi writer Douglas Adams, who famously claimed that number 42 is the last answer of life, the Universe, and all.
“For the first time ever, we are able to identify the date and environmental impacts of the last magnetic pole shift,” said Earth scientist Chris Turney from the University of New South Wales in Australia.
“The findings were made possible by old kauri trees from New Zealand, which have been preserved in sediments for more than 40,000 years. Using the old trees we could measure, and head the spike in atmospheric radiocarbon levels caused by the fall of the Earth’s magnetic field. “
This latest era of magnetic rotation is called the Laschamp event, and we call it the geomagnetic journey. This is when the planet’s magnetic poles change positions shortly before returning to their original position. This is one of the best field events studied on Earth, recorded with ferromagnetic minerals.
This happened about 41,000 years ago, and lasted about 800 years. But it was not clear what effect this event had on life on the planet – so when scientists discovered an ancient kauri tree (Agathis australis) in 2019 that had survived this period, they took the opportunity to learn more.
That’s because trees record atmospheric activity in their annual growth rings. In particular, carbon-14, or radiocarbon, can reveal a great deal of information about celestial activity.
Radiocarbon only appears on Earth in trace amounts compared to the other naturally occurring carbon isotopes. It is formed in the upper atmosphere by the explosion of cosmic rays from space. When these rays enter the atmosphere, they interact with the local nitrogen atoms to create a nuclear reaction that produces a radiocarbon.
Since cosmic rays are constantly flowing through space, the Earth receives a stable or reduced supply of radiocarbon. Thus, a spike in radiocarbon in tree rings tells us that the Earth was more exposed to radiocarbon in that year.
When the Earth’s magnetic field is weakened, as it was at the Laschamp event, more cosmic rays pass through to the atmosphere to produce more radiocarbon. Because of this, scientists had previously been able to discover that the Earth’s magnetic field had weakened to about 28 percent of its normal strength 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 incident occurred about 42,200 years ago, and the magnetic field was at its weakest before Laschamp event.
“Earth’s magnetic field dropped to just 0-6 percent strength during the Adams Event,” Turney explained. “Of course we didn’t have a magnetic field at all – our cosmic radiation shield was completely gone.”
During this time, the solar magnetic field would have weakened several times, because, too, it experienced a magnetic shift as part of its regular cycle. These times see less sunspot activity and flare, but the sun ‘s magnetic field also provides a measure of protection for the cosmic rays – so during the lowest sunlight, a cosmic ray explosion would have gone the size again.
This weak magnetic field would have triggered major changes in the Earth’s atmospheric ozone, with dramatic results, including dramatic electric storms and aurorae, and global climate change.
“Undeveloped radiation from space ripped air particles in the Earth’s atmosphere, separating electricity and emitting light – a process called ionization,” Turney said.
“The icy air covered the ozone layer, triggering global climate change.”
This is consistent with climate and environmental changes from this period that have been seen in other records from around the globe, such as the mysterious extinction of Australia’s megafauna.
Oddly enough, it also coincides with the oldest cave art we have ever had, prompting the researchers to think that the Adams Event may have led people inside. .
“This sudden behavioral shift in very different parts of the world is consistent with the use or change in caves at the Adams Event, possibly as a refuge from ultraviolet B elevation, which may be to levels harmful, during minso grandsolar or energetic solar particles, which may also explain increased use of och red sunlight, ”they wrote in their paper.
That’s somewhat speculative, of course, but it shows that geomagnetic transformation can be a radically changing event around the world. And recent evidence has suggested that we are currently close to another.
This, the researchers say, could be completely catastrophic in the current situation.
“Our sentiment is already filled with carbon at levels never seen by humanity. The turning of a magnetic pole or a dramatic change in solar activity would be the unprecedented accelerations of climate change,” Turney said.
“We need to reduce carbon emissions quickly before it happens again at random.”
The research was published in Science.