Present true polar wander in the frame of the Geotectonic Reference System

The Mesozoic-Cenozoic evolution of the Earth's lithosphere reveals a fundamental hemispherical symmetry inherent in global tectonics. The symmetry is documented by the concurrent regular growth of the Pacific and African plates over the past 180 million years, and by the antipodal position of the two plates. The plates are centered on the equator, where center P of the Pacific plate is located at 170A degrees W/0A degrees N, and center A of the African plate at 10A degrees E/0A degrees N. P and A define a system of spherical coordinates, the Geotectonic Reference System GRS, which shows a distinct relation to Cenozoic global tectonics. P and A mark the poles of the geotectonic axis PA. The degree-two pattern of the residual geoid displays two major highs, the Pacific high and the African high. Poles P and A are located in the centers of the respective geoid highs. The stable configuration of excess masses m(P) and m(A) which are responsible for the two geoid highs results in the long-standing stability of location of the geotectonic axis PA. The Earth's rotation axis is oriented perpendicularly to the PA axis. Owing to the extraordinary stability of the geotectonic axis, any change of orientation of the rotation axis, e.g. induced by post-glacial rebound, occurs in such a way that the axis remains in the equatorial plane of the geotectonic system, i.e. in the 80A degrees W/100A degrees E meridional plane. Observed present polar wander is directed towards 80A degrees W (79.2 +/- 0.2A degrees W). This indicates that the present true polar wander is directed exactly along the GRS-equator, identical with the 80A degrees W/100A degrees E great circle of the Earth. It is concluded that the phenomenon of polar wander is basically related to the symmetry of the geotectonic system defined by the Pacific pole P, at 170A degrees W/0A degrees N, and the African pole A, at 10A degrees E/0A degrees N.