Support WBURAncient Trees Show When The Earth's Magnetic Field Last Flipped OutPlay03:06Download AudioNell GreenfieldboyceFebruary 18, 2021 ShareA giant kauri tree grows in Waipoua Forest in Northland, New Zealand. Trees like this one that fell long ago and were preserved for thousands of years are helping researchers discern fluctuations in the Earth's magnetic poles. (Getty Images)
