Brunhes–Matuyama reversal

The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal. Opinions vary as to the abruptness of the reversal: it may have occurred over several thousand years, or much more quickly, perhaps within a human lifetime.