CONTINENTAL-DRIFT AND TRUE POLAR WANDERING

Summary. Evidence in the form of 75 yr of ILS data is accumulating which suggests that true polar wander may be currently taking place. It seems likely that true wander of some magnitude must always accompany plate motions, but the extrapolated ILS rate is an order of magnitude larger than the rate of true polar wander deduced from palaeomagnetic data over the past 55 Myr. The conflict between palaeomagnetic and latitude data provides the motivation for investigating one possible excitation of polar wander, the mass redistribution which accompanies continental drift. The mass redistribution arises mainly because of the contrasting density structure of oceanic and continental regions. The change in the inertia tensor resulting from 106yr of plate motions is found to be negligibly small; even consideration of episodic plate movements, anelasticity, or a decoupled lithosphere cannot boost the effect to the ILS rate of polar wander. These conclusions are strengthened by the fact that any one of several absolute plate velocity models, based on extremely diverse assumptions, yields the same results. In contrast, preliminary findings regarding the effect of Pleistocene deglaciation activities on the inertia tensor reveal that such non‐isostatic phenomena may have a large influence on polar wander. Copyright © 1979, Wiley Blackwell. All rights reserved