ABSTRACT
Many Europeans, from early Greek philosophers to Renaissance cartographers to eighteenth-century capitalists, believed in the existence of a Great Southern Land that counterbalanced the northern hemisphere landmasses, thereby ensuring the earth rotated smoothly like some perfectly tuned flywheel. In R. A. Cook’s words, ‘this Southern Continent must lay within the Polar Circle where the sea is so pestered with ice that the land is thereby inaccessible’. Plate motion circuits connect plates that share boundaries, and well-constrained plate motions from one part of a circuit can be used to infer plate motions of other plates on the circuit whose motions are either unknown or uncertain. Plate motions about spreading centres are well constrained and the directions and rates of movement can be accurately calculated from fracture zones and magnetic anomalies. Analysis of the offshore Pacific-Australian-Antarctica plate circuit leads to an estimation of 850 km of relative displacement between the Australian and Pacific plates.
