DID RODINIA HAVE THE SAME SHAPE AS PANGEA AND COLUMBIA?

A variant of the AUSWUS and AUSMEX configurations gives Rodinia the same general shape as Pangea, which was elongate north–south and underwent compressive orogeny along its entire western margin. This shape would have occurred in Rodinia if western South America extended north of Baltica (present orientation) and Grenville-age belts connected from Baltica through eastern North America to belts of similar age in Australia and coastal East Antarctica. A similar configuration has also been proposed for the older (1.8–1.5-Ga) supercontinent Columbia, which had a compressive margin stretching from Baltica through eastern and southwestern North America to the western margin of South America. All three supercontinents also had similar margins on the sides opposite to the long compressive ones. Pangea had an eastern margin divided between rifting in the south (Gondwana) and accretion of the rifted terranes to the north (Laurasia). In Columbia, terranes rifted from southern Africa and India (part of Ur) apparently collided with the Congo and similar areas in central Africa (margin of Atlantica). Rifting of Rodinia may have occurred along the western margin of North America and the northern margins of India and Australia, with accretion beginning in North Africa (all in present orientations). In all three of the supercontinents, marginal rifting occurred in the older part and accretion to the younger part. The nearly identical shapes of the three supercontinents suggests that this configuration is the stable one for landmasses that contain virtually all of the earth's continental crust. Apparently they require long zones of subduction in order to accrete, and the rifting on the other side of the older regions of the supercontinent may be a remote result of this compression.