Ancient Tree Discovered With Record Of Earth’s Magnetic Field Reversal In Its Rings

In New Zealand, an ancient tree has been discovered that carries evidence of a reversal of Earth’s magnetic field. During an uncovering for the expansion of a geothermal power plant on New Zealand’s North Island, the Agathis Australis tree was found, or better known as a Kauri tree in Māori.

Buried 26 feet deep into the soil, the tree is 65 feet tall with a diameter of eight feet. The tree was alive between 41,000 and 42,500 years ago for about 1,500 years, the carbon dating revealed.

“There’s nothing like this anywhere in the world,” Alan Hogg, from New Zealand’s University of Waikato, said. “This Ngāwhā kauri is unique.”

The period in which the tree was alive was a time in Earth’s history when the magnetic field nearly reversed. The magnetic north and south did not quite conclude a full reversal as they went on an excursion.

The iron in the core of the Earth is believed to generate the magnetic field. The movement of the Earth causes electric currents that extend far into space. Protecting Earth from the solar wind, the magnetic field serves as a barrier. The solar wind is a stream of charged particles from the Sun that could possibly strip away the ozone layer if it were to impact the atmosphere.

More radiation from the Sun could get through when the magnetic field reverses (or tries to). Scientists have linked extinction events to magnetic field reversals before.

This is the first time that a tree was found that lived through the near reversal. The kauri tree rings show complete evidence of the near reversal. “It’s the time it takes for this movement to occur that is the critical thing. We will map these changes much more accurately using the tree rings,” Hogg said.

Kauri tree
The kauri tree unearthed during the expansion of the Ngāwhā Generation geothermal power plant. NELSON PARKER

Chris Turney, an expert in paleoclimatology and climate change from the University of New South Wales, is leading of group of scientists who are analyzing samples of the tree. Getting insight into what happened to the tree during the near magnetic reversal could be helpful in case it happens again. “We will have increased cosmic radiation. It will take out satellites and it might take out other communication infrastructure,” according to Hogg.

Turney said: “The precious thing is this huge, lonely tree grew for some 1700 years across a remarkable period in our planet’s history when the Earth’s magnetic field flipped some 42,000 years ago, a period known as the Laschamp Excursion. Funded by the Australian Research Council we’re undertaking detailed measurements of the radioactive form of carbon through the tree rings.”

Despite the fact that in the last 20 million years it appears that the magnetic reversals have been happening once every 200,000 to 300,000 years (according to NASA), it could theoretically happen randomly. The most recent full reversal happened about 780,000 years ago.

Not long ago, scientists revealed that the magnetic north pole had moved unexpectedly. Usually, the tracking goes steadily from the Canadian Arctic to Siberia, but it sped up so much that the researchers had to renew the World Magnetic Model (WMM). The WMM is a representation of Earth’s magnetic field that is used worldwide by GPS systems.

“Because the Earth’s magnetic field has a major effect on how much radiocarbon carbon is formed in the upper atmosphere, these precious analyses will allow us to investigate the magnitude and rate of change when the magnetic field reversed during the Laschamp; something not possible before and of great interest given recent changes in the Earth’s magnetic field,” Turney said.

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