Earth's poles shifted surprisingly fast during the age of dinosaurs, ancient sea levels reveal

The location of Earth's geographic poles has changed several times over the past 320 million years in a process known as true polar wander, according to measurements of ancient flooding brought about by sea level changes resulting from our planet's crust shifting relative to Earth's spin axis.

Such a shift can affect climate, both on local scales and globally, as regions that were by the poles find themselves moving down to lower latitudes and vice versa.

This can then affect atmospheric circulation patterns, which affect climate across the world.

The changes would have affected the environments in which life developed and evolved, from the age of the dinosaurs through to some of our oldest primate ancestors.

True polar wander is not the same as a change in the rotational axis of the Earth .

Currently, Earth spins at an angle of 23.4 degrees relative to the plane of its orbit around the sun, and this rotational axis can vary periodically over tens of thousands of years as a result of the Milankovitch cycles caused by the gravitational pull of the sun and planets.

True polar wander is different.

Here, the angle of Earth's spin axis does not change relative to its orbital plane.

Instead, Earth's crust and mantle shift relative to that rotational axis.

This is because Earth is not perfectly spherical.

Instead, it is oblate, with Earth's rotation causing the equator to bulge out and the poles to slightly flatten.

Because Earth is not spherical, it has multiple axes of inertia, the largest one being aligned with the rotational axis.

These axes need to be balanced to prevent Earth's rotation from becoming chaotic.

However, plate tectonics and indeed the Milankovitch cycles can upset that balance of mass, for example by causing more continental crust to congregate in one hemisphere than another.