Hi EQF. I think what you’re looking for is known as the Chandler wobble.

The Chandler wobble, named for Seth Carlos Chandler Jr., the scientist who discovered it in 1891, is one of several motions exhibited by Earth as it rotates on its axis, much like a top wobbles as it spins. While many of the wobbles are explained, the cause of the Chandler wobble has vexed scientists for years.

The wobble, which has been under observation for more than a century, has a period of about 433 days. In other words, it takes 1.2 years to complete one wobble. The amplitude of the wobble amounts to about 20 feet at the North Pole.

It has been calculated that the wobble would dampen down and cease to exist in 68 years unless some force constantly acted on it to reinvigorate it.

Previous explanations of that force have ranged from changes in snow cover and river runoff to interaction at the boundary of Earth's core and its surrounding mantle to earthquakes. None of these hypotheses panned out.

Check the link to see the cause. Take Care…Don in creepy town

• Chandler wobble