Paul Voosen in Science:
Several years ago, workers breaking ground for a power plant in New Zealand unearthed a record of a lost time: a 60-ton trunk from a kauri tree, the largest tree species in New Zealand. The tree, which grew 42,000 years ago, was preserved in a bog and its rings spanned 1700 years, capturing a tumultuous time when the world was turned upside down—at least magnetically speaking.
Radiocarbon levels in this and several other pieces of wood chart a surge in radiation from space, as Earth’s protective magnetic field weakened and its poles flipped, a team of scientists reports today in Science. By modeling the effect of this radiation on the atmosphere, the team suggests Earth’s climate briefly shifted, perhaps contributing to the disappearance of large mammals in Australia and Neanderthals in Europe.