The magnetic field that protects our planet from solar and galactic radiation, the dangerous rays that can harm things on our planet, is generated in the outer core. As energy travels through that core it creates an electrical current, which in turn creates a magnetic shield that goes far out into space. In the 1980s, scientists started to send satellites up into the atmosphere and get these little glimpses of what was happening to the magnetic shield. Through math, they are able to take those calculations from outer space and look at what’s happening inside this molten outer core, where the field is generated.
What they have found is phenomenally surprising. There is this absolutely tortured bunch of magnetic fields within the core. You’ve got the two pole magnetic fields that protect our planet, the North and South poles, but within this molten core there are all these factions, like the battle of the Titans, that are trying to topple the dipole. If they succeed, which they’ve done hundreds of times in the planet’s history, then the North and South poles will switch places.
Brunhes was a geophysicist who wanted to trace the Earth’s magnetic field over time. To do that, he needed a unique formation: a thick piece of undisturbed terra cotta that had then been covered by hot basal lava from a volcano. When terracotta is heated up, then cools down, some of the electrons in its molecular structure, will become fossil magnets. They will lay down the coordinates of the magnetic field on that exact spot of the Earth at that precise time, so you can see very precisely what was happening.
Brunhes lived near Puy de Dome in the Massif Central, in the middle of France, where there are all these extinct volcanoes. Word comes back from one of his friends, who was a road cutter, saying, “I just cut a road in this place called Pontfarin, and it showed just exactly what you’re looking for.” Brunhes packs his chisels, gets on his horse, rides for at least a day, then chisels out some pieces of the terra cotta with the basalt over the top of it, and takes it back to his laboratory.
What he discovers in the terra cotta is that when this terracotta got super- heated, and then cooled again, the poles were on different sides of the planet
https://en.wikipedia.org/wiki/Geomagnetic_reversal