Location of upwelling in Earth’s mantle discovered to be stable

A new study shows that large-scale upwelling within Earth’s mantle mostly occurs in only two places: Beneath Africa and the Central Pacific. These upwelling locations have remained remarkably stable over geologic time, despite dramatic reconfigurations of tectonic plate motions and continental locations on the Earth’s surface. The study describes a plate tectonic “quadrupole,” which defines two points of “net convergence” and two points of “net divergence” of tectonic plate motions.
Source: http://www.sciencedaily.com/releases/2013/06/130626142936.htm