Hot liquid that churns around Earth’s outer core powers a gigantic magnetic field that’s been hugging our planet since its infancy, protecting it from harmful solar radiation. But this magnetic field is known to get restless — and a couple of times every million years or so, the poles flip, and magnetic south becomes magnetic north and vice versa.
Yasemin Saplakoglu | SPACE.com
Now, a new study suggests that the magnetic poles can flip much more frequently than scientists thought. That’s what seems to have happened around 500 million years ago during the Cambrian period, when Earth’s creatures were undergoing evolutionary growth spurts, transforming into more complex life-forms.
To understand the workings of the magnetic field during this time, a group of researchers from the Institute of Physics of the Globe of Paris and the Russian Academy of Sciences collected sediment samples from an outcrop in northeastern Siberia.
In the lab, they determined the orientation of magnetic particles trapped in the sediments by slowly heating them to extreme temperatures to demagnetize them. The orientation of the particles corresponded to the magnetic field direction (which way magnetic north pointed, for instance) at the time and place the sediment was deposited. The researchers fine-tuned the age of the sediments by dating trilobite fossils found in the same layers, and were thus able to approximate when the magnetic fields flipped.