Comparison between the hot spot and geomagnetic field reference frames

Abstract

Hot spots are located on the Earth's surface and are caused by hot plumes of upwelling mantle material. They manifest themselves by volcanic activity which changes its location in response to the movement of the lithosphere over the mantle plume. It has been suggested^1–3 that hot spots are relatively stationary with respect to each other, and also that they represent a frame of reference with which to measure the absolute movement of the lithospheric plates over the surface of the Earth. Another frame of reference can be partially defined by the position of the mean magnetic dipole field of the Earth. As the dipolar field is believed to be closely related to the spin axis, this frame of reference automatically gives information about the palaeolatitude and orientation of the lithospheric plates. But since the position of the ancient dipole field of the Earth does not give any information about palaeolongitude, and since in many cases the definition of the field is relatively poor due to less than adequate rock collections during the time of interest, hot spot reference frames have been favoured by many people. We now report a comparison of the two frames of reference and show that over the past 200 Myr there has been relative movement between the two frames of reference of about 20°, and that this motion has not been constant with time.