STICK a penny to the edge of a spinning top and its axis of rotation will shift. Now evidence is emerging that something similar may have happened more than once to the Earth.
The clumping of ancient continents in one hemisphere would have unbalanced the Earth and caused its axis to slowly migrate, geologists suggest. This would mean that a land mass formerly at one of the poles, for instance, would appear to have slipped across the Earth’s surface. Evidence for this “true polar wander” is sparse because it is hard to distinguish from the normal drift of continents associated…
