The actual idea of continental drift has never been accepted – what we have in the consensus theory of Plate Tectonics is something more subtle. In this all the plates move but in different directions and at different speeds, and the plates consist of both continental crust as well as the attached sea floor bottom. In Wegener's theory it was just the continental crust that moved, and Africa, it was said, was formerly joined to South America and NW Europe to Newfoundland and the Appalachians. Now, it is known that sea floor spreads from mid ocean ridges and in order to compensate for the continuous process of new sea floor forming it is projected that at some plate boundaries subduction occurs. Subduction is also a feature of mountain forming, where one plate is thought to run under another and bend downwards into the mantle where it is swallowed up. However, the consensus hypothesis would have it that the plates are in constant motion, a necessary prerequiste to account for the fact that warm temperature fauna and flora has been found in fossils from the far north. Hence, it an essentail that plates are in motion. However, in an alternative theory, that of the expanding earth model, the plates are said not to move, and the mid ocean ridges are where material from the mantle is thrust up to the surface, but the continents remain stationary. It is the oceans that are expanding. At continental boundaries, such as along the western coast of the Americas, mountains are rising but not as a result of subduction but because continental crust has to come to terms with earth expansion (seee www.platetectonicsbiglie.blogspot.com/2011/11/plate-movement-of-plate-te… and http://earthexpansion.blogspot.com December 31st, 2011, 'Folding, plate tectonics and the impossible dream'.
However, looking around at conventional sources on Plate Tectonics I came across http://geodesy.hartrao.ac.za/site/resources/plate-tectonics-overview.html where it claims that the rate of movement has been measured by GPS and other methods. Are they measuring the rate of expansion or the movement of the plates?