evidence: When Earth’s magnetic poles flip it could be "chaos" for future humans [...] One of the most interesting discoveries about Earth in the past few decades concerns the Earth’s magnetic poles. Paleomagnetic records show that the poles have flipped places 183 times in the last 83 million years. That’s about every 450,000 years on average, though there were ten million years between flips in at least two cases. [...] When the poles flip, scientists call it a geomagnetic reversal, and the last one happened about 780,000 years ago. It takes between 2,000 and 7,000 years for the poles to reverse. The evidence is contained in magnetic minerals inside rocks. Magnetic minerals record the strength and direction of Earth’s magnetic fields when they’re locked in place, either as sediments or in magma. The study of magnetism in Earth’s ancient rocks is called paleomagnetism.