True polar wander (TPW) is a mechanism, which describes a change in the spin axis of a planetary body.
It means that the geographic locations of the North and South Poles change, or “wander.”
This shift of the whole celestial body – relative to its axis of spin – takes place because of changes in the mass distribution of planet or moon – how much of its mass is located where.
If the poles wander through a large angle, places that were formerly warm will become cold and, likewise, some regions that were not tropical will be moved into the tropic zone.
By the time the rotation settled down, the north-south axis would have re-oriented to pass through different points on the surface.
Earth has undergone several periods of polar wander in the past and the phenomenon has also been detected on Mars, Enceladus, and Europa.
Large TPW events are rare and happen over millions of years. However small amounts of such polar wander can be detected on time scales of months or years and can be influenced by natural climate cycles and human-caused climate change on our planet.
There are several known Causes of true polar wander include among others asteroid impacts, postglacial crustal rebound, change in the core-mantle boundary topography and several others.
The concept of polar wander regarding the planet Earth, was first proposed about 140 years ago. It was already known to astronomers in the nineteenth century that the precise locations of the geographic poles are continuously drifting or wandering across the Arctic and Antarctic landscapes.
But one thing we have to remember: True polar wander and sudden reversal of Earth’s magnetic field are different phenomena with different causes, and should not be confused.