The Day the Magnetic Poles Switched Places -- and When it Will Happen Again
The most expensive wood in the world is found in a swamp.
New Zealand's Kauri trees are highly prized as building material. They're remarkably durable with elaborate grain patterns and rich colors sought after by ship builders and building contractors -- even makers of fine musical instruments.
Of course, living Kauri trees aren't found in a swamp. They're in forests, as you'd expect. But there's another kind of Kauri even more valuable, an ancient relic thousands of years old -- a kind that last saw the sun before humans built their first city. Over thousands of years, Ancient Kauris were gradually buried under New Zealand's Northland bogs. And they're giants. Some of them grew over 160 feet high, and their trunks can be as wide as sixteen feet.
While highly sought after for construction, Ancient Kauri logs have a much more profound value to science - particularly geologists, or anyone interested in what happened thousands of years ago. You may be familiar with the astounding accuracy of tree rings for marking history. Seems trees in temperate climates grow exactly one ring a year. It's more accurate than carbon dating. But the jackpot find is a tree that lived before humans were around to report what happened.
By this measure, the Ancient Kauri are a treasure trove. A well-preserved log can have 2,000 years of rings in its trunk. If a log has been preserved in that swamp for over 40,000 years, they are a literal time machine. Ancient Kauri rings can date to the exact year events science can only guess at otherwise. And in 2019, workers preparing a site for a new power plant in Northland accidentally unearthed one of these amazing specimens.
It was a 42,000 year-old kauri tree, perfectly persevered, a full 8 feet in diameter. By taking detailed radiocarbon data from each of its 1,700 rings, researchers were able to create an unbroken timeline of the Earth's atmosphere during a key time in the planet's history.
The results confirmed a crazy event geologists were aware of from studying volcanic rock, deep sea sediment, and ice cores: there was a time the Earth's magnetic poles switched places. The North Pole was, well, where the South Pole is today. Seems incredible. Yet it happened 42,000 years ago. And because some workers found an ancient log in a swamp, scientists now know the exact start and end date of this strange occurrence -- what's called the Laschamps Excursion.
Through their analysis of the tree rings, researchers modeled the effects on the atmosphere as the Earth's magnetic field gradually weakened, dramatically falling to 6% of its normal levels. It's this loss in the protective field that caused the poles to flip.
We should be glad we didn't live when this happened. The Laschamps Excursion took almost a thousand years. And in that time, there were centuries when the magnetic field around the Earth was weak, letting in deadly cosmic radiation, causing electrical and solar storms, and impacting the DNA of all life. The Research Team theorized this loss in magnetic field strength may have contributed to the disappearance of large mammals, and even hastened the end for Neanderthals. Could be this magnetic shift helped kill off an entire species of human.
That's what makes the South Atlantic Anomaly so concerning.
It was first reported in 1958, the first time we had satellites that could see it. The Earth's magnetic field seemed to be weaker in a region over the South Atlantic.
It's something scientists keep a close eye on today. The European Space Agency deploys swarms of satellites to measure the field strength. In the last couple of years, scientists noted a new, concerning development. The area where the magnetic field is weakening appears to be dividing into two separate areas. This is exactly the kind of thing that could trigger a long-term geomagnetic transition.
In other words, that event where the poles shift places? It may be happening right now.
