Earth's geographic poles have undergone four major shifts in 320 million years

A new study published in the journal Science reveals that Earth's geographic poles have experienced four significant episodes of movement over the last 320 million years. This phenomenon, known as true polar wander, occurs when the Earth's outer layers—the crust and mantle—shift in relation to the planet's core to maintain balance around the axis of rotation.

Changes in mass distribution, such as the movement of tectonic plates or the melting of ice caps, can disrupt the planet's equilibrium. Lead author Matthew Domeier, a geophysicist at the University of Oslo, noted that satellite measurements confirm this process is ongoing today at a rate of approximately ten centimeters per year, primarily driven by melting ice sheets.

To distinguish true polar wander from tectonic plate movement, researchers utilized a new method studying ancient sea-level changes. Because Earth is not a perfect sphere and is slightly bulged at the equator, shifts in the poles affect how mass is distributed relative to the rotation axis.