Earth's continents seem to be drifting westward by around 0.2 degrees every million years. This is a sign that the planet is experiencing true polar wander — the rotation of Earth's solid outer layer relative to its spin axis.
To distinguish true polar wander from the overlapping motion of individual tectonic plates, Pavel Doubrovine and his colleagues at the University of Oslo defined a new global reference frame, which they consider to be accurate for the past 120 million years. To do so, the researchers used the computed tracks and present positions of volcanic hot spots in the Pacific Ocean and the Indo-Atlantic hemisphere. The rate of true polar wander has increased systematically over the past 40 million years, the team found.
J. Geophys. Res. http://dx.doi.org/10.1029/2011JB009072 (2012)