True polar wander
A re-orientation of the solid Earth as a whole relative to the spin axis is called true polar wander. It is caused by changes in the mass distribution of the Earth. We model true polar wander, for example due to the changing distribution of subduction through Earth history. Modelling results are compared with observation-based polar wander, which is inferred from differences of plate motions in the paleomagnetic frame, and in the reference frame of the Earth mantle (Figure 1). For the last ~120 million years, the mantle reference frame can be deduced from hotspot tracks (more information on the page “Hotspot tracks and other reference frames for plate tectonics”) (Doubrovine et al., 2012), for the period prior to that, true polar wander can be derived from coherent rotations of the continents in the paleomagnetic reference frame (Torsvik et al., 2012; Figure 2). In the movie on this page, created by Pavel Doubrovine, you can see the movement of the continents and true polar wander. The latter is represented by the movement of the grid shown relative to the vertical axis. Discrepancies between modelled and observation-based polar wander can for example be due to deficiencies in the subduction history model (Steinberger et al., 2017).
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