Construction workers in New Zealand were in for a surprise when they uncovered a 40,000-year-old swamp kauri tree during a geothermal energy plant expansion project. The ancient tree, which lived through a near-reversal of Earth’s magnetic poles 42,000 years ago, provides new insight into what happens during a magnetic pole reversal, an event that occurs every 200,000 to 300,000 years.

Earth’s magnetic field, which acts as a barrier against solar wind, is generated by the iron in the planet’s core. During a magnetic pole reversal, the magnetic field weakens and solar radiation penetrates, leading to major extinction events. The last pole reversal occurred 780,000 years ago, and scientists have warned that the magnetic north pole is already moving towards Russia, signaling the beginning of a total pole reversal.

The swamp kauri tree, 65 feet long and 8 feet wide, was preserved as if it were in a swamp, even though it wasn’t. The radioactive carbon in the tree rings gives a complete record of the near-reversal of Earth’s magnetic fields that happened during its lifetime, providing scientists with a unique opportunity to understand the effects of magnetic pole reversal on the planet.

Alan Hogg, from the University of Waikato in New Zealand, says that the tree will help map changes in the magnetic field much more accurately. The lines of the magnetic field can become jumbled and cross each other during a pole reversal, causing chaos and weakening their ability to protect against solar radiation. Scientists are working to create models to determine what the effects of magnetic pole reversal will look like on a practical level.

The journey of the poles from one end to the other can take several thousand years, but it has already been happening for 3,000 years. The failure of Earth’s magnetic shield will have dire consequences, as communications satellites in high orbits will go down, followed by astronauts in low-Earth orbit who won’t be able to contact home. Finally, cosmic rays will start bombarding every human on Earth.

This ancient tree provides an unparalleled opportunity for scientists to understand the impacts of magnetic pole reversal on the planet and its inhabitants. While the reversal is not expected to happen in the next million years, it is not something that can be ruled out in the next hundred. The 40,000-year-old swamp kauri tree will help scientists determine what to expect and how to prepare for the inevitable change.

The discovery of this ancient tree has opened up new avenues of research into Earth’s magnetic field and the impact of magnetic pole reversal. Scientists are using the tree to understand the changes that will take place during the pole reversal and what the consequences of those changes will be. With the poles already moving, this research could not be timelier, and the findings will be crucial in preparing for the future.