An ancient tree has a lot to teach us about Earth's magnetic field

An ancient tree unearthed on New Zealand’s North Island could contribute to a better understanding of how Earth’s fickle magnetic field works, as Newsweek reports.

The tree goes by its Māori name, kauri, and it’s big at 65 feet tall and eight feet in diameter. It’s also old. Furthermore, carbon dating revealed that the kauri lived for 1,500 years at just over 40,000 years ago. The discovery makes it one of the oldest trees ever found.

The time frame is important, as scientists believe that a near reversal of Earth’s magnetic field took place at this time with the tree living through the entire event. At that time, between 41,000 and 42,500 years ago, the planet’s North Magnetic Pole traveled down into the Southern Hemisphere. This would have wreaked havoc on the planet’s magnetic field.

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A Solar Windshield

Experts believe that Earth’s magnetic field loops out from the molten iron in the planet’s core. As the liquid metal churns, it creates a magnetic field that extends out into space. The field is crucial in protecting the Earth from the solar wind, a cosmic cascade of charged particles shot out by the Sun. Without the field, the solar wind could whisk away the ozone layer.

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Usually, the magnetic field acts as a barrier against the solar wind. However, during a full or partial reversal, the field weakens and allows dangerous radiation to infiltrate the atmosphere. Researchers believe that past magnetic field reversals have contributed to extinction events.

Learning from a Tree

These facts illustrate why the discovery of the ancient kauri, which contains a complete record of the reversal in its rings, is so vital to understanding the impacts of a magnetic reversal. “It’s the time it takes for this movement to occur that is the critical thing,” Alan Hogg of New Zealand’s University of Waikato told Stuff.nz. “We will map these changes much more accurately using the tree rings.”

Moving forward, scientists will analyze samples from the kauri to understand better what happened to the tree during the reversal. The study will offer insights into what will happen when a reversal eventually takes place in the modern era. Because it’s not a question of whether or not this will happen, but rather when.

Is a Reversal on the Horizon?

Magnetic field reversals happen randomly. However, over the last 20 million years, a pattern has emerged. Reversals seem to take place every 200,000 to 300,000 years. The last full reversal occurred 780,000 years ago, which means Earth is overdue for another.

Recently, researchers revealed that the North Magnetic Pole shifted dramatically. So much so, that scientists had to reconfigure the World Magnetic Model (WMM), which is crucial in the workings of technology like GPS.

As the shifting of the WMM shows, a reversal of Earth’s magnetic field and the subsequent solar radiation bombardment could have devastating consequences on the world’s technological systems.

“It will take out satellites, and it might take out other communication infrastructure,” Hogg said. But with the knowledge gleaned from the wise old kauri, the world can be better prepared for such an event.

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