Geologists at Rice University have uncovered evidence that suggests Earth’s spin axis was in a different spot millions of years ago, a phenomenon called “true polar wander.” The change, which occurred sometime in the past 12 million years, would have shifted Greenland further up into the Arctic Circle — which may have contributed to the onset of the last major Ice Age, 3.2 million years ago.
You can think of the Earth’s spin axis as the invisible axle around which the planet spins. This axle has always stayed the same relative to the sun, giving our Earth its characteristic axial tilt. But the places this imaginary axle emerges from the Earth’s surface — the North and South poles — haven’t always been the same. Those points have shifted at various times in our planet’s history, meaning that the true poles have been in different places.
The new evidence for one of these shifts comes from an analysis of millions of years of data left behind in the geological record: in the path of hotspots like Hawaii and in sediments and magnetic fields from the sea floor.
