. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography gin of the continents), Pangaea covered 40 percent of the earth while the universal ocean, Panthalassa (the ancestral Pacific I covered the remainder. With Africa as the heart- land, the continents were generally farther south and farther east than today. New York and London were only slightly north of the equator. The ovoid plan of Pangaea was interrupted by a great bight called the Sea of Tethys which separated Eurasia from Africa. The breakup and
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography gin of the continents), Pangaea covered 40 percent of the earth while the universal ocean, Panthalassa (the ancestral Pacific I covered the remainder. With Africa as the heart- land, the continents were generally farther south and farther east than today. New York and London were only slightly north of the equator. The ovoid plan of Pangaea was interrupted by a great bight called the Sea of Tethys which separated Eurasia from Africa. The breakup and dispersal of the continents can best be visualized in a general way by reference to Figure 5. There the drift is shown in absolute coordinates as con- trolled by "hot spots"—plumes of lava which have pierced AN TAPC Ti. Figure 4—The Antarctic plate, because it is surrounded entirely by a system of ridges and transform faults and without any trench, is the most fixed of all of the plates, but has grown ever larger by peripheral addition of new oceanic crust. The detachment of Australia and Africa from Antarctica and their northward drift has been accommodated by migrating, mid-ocean ridges which have moved one-half the velocity of the drifting continents. the lithosphere and laid down strings of islands as the crust moved over a fixed hot spot—or one at least assumed to be fixed. This effect can best be observed in the case of the Hawaiian Chain where a stream of islands and sea- mounts extends from Hawaii to Milwaukee Seamount, well past Midway Island. There are other methods of tracking the drift of continents (magnetic reversal anomalies on the ocean crust; the strike of fracture zones; and matching conjugate points on opposing continental margins across a rift ocean, , the South Atlantic), but these methods give only relative solutions to drift rota- tions. The major aspects of drift can be summarized as fol- lows. The Atlantic Ocean (including the Gulf
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