 However, the existence of a globally fixed reference frame for island-seamount chains and aseismic ridges ("traces") that are inferred to have originated from hotspots was quickly discounted by the primitive plate reconstructions available in the mid-1970s (Molnar and Atwater, 1973).Further, paleomagnetic measurements imply that hotspots have moved relative to the magnetic poles of the Earth (the magnetic poles are further inferred to correspond with the rotational poles of the planet when averaged over thousands of years).Aside