![]() Those who appreciate the overall fit of continents call the evidence "compelling," while others who note gaps, overlaps, or emissions remain skeptical. Reconstructions have been shown to be geometrically feasible which are preposterous to continental drift (e.g., rotation of eastern Australia fits nicely into eastern North America). There are a number of ways to fit Africa, India, Australia, and Antarctica (only one can be correct!). There are, however, areas of overlap of continents and one large area which must be omitted from consideration (Central America). The "Bullard fit" 2 gives one of the best reconstructions of how Africa, South America, Europe, and North America may have once touched. Recent investigators have used computers to fit the continents. Especially interesting is how the eastern "bulge" of South America can fit into the southwestern "concavity" of Africa. The idea that the continents can be fitted together like a jigsaw puzzle to form a single super continent is an old one. At this rate it would take 100 million years to form an ocean basin or mountain range. In conformity with evolutionary-uniformitarian assumption, popular plate tectonic theory supposes that plates move very slowly - about 2 to 18 centimeters per year. Subduction occurs where two plates are converging with one plate underthrusting the other producing what is supposed to be compressional deformation (e.g., the Peru-Chile Trench and associated Andes Mountains of South America). Transform faulting occurs where one plate is slipping horizontally past another (e.g., the San Andreas fault of California and the Anatolian fault of northern Turkey). Sea-floor spreading occurs where two plates are diverging horizontally (e.g., the Mid-Atlantic Ridge and East Pacific Rise) with new material from the earth's mantle being added between them to form a new oceanic crust. Deformation occurs at the margins of plates by three basic types of motion: horizontal extension, horizontal slipping, and horizontal compression. The outer lithospheric shell of the earth consists of a mosaic of rigid plates, each in motion relative to adjacent plates. ![]() The popular theory of drifting continents and oceans is called "plate tectonics." 1 (Tectonics is the field of geology which studies the processes which deform the earth’s crust.) The general tenets of the popular theory may be stated as follows. This "revolution" in our concept of the earth's character is a striking commentary on the human nature of scientists and on the flexibility that scientists allow in use of the geological data. The theory of moving continents is now the ruling paradigm and those who question it are often referred to as stubborn or ignorant. ![]() The handful of geologists who promoted the notion of continental drift were accused of indulging in pseudoscientific fancy. Twenty years ago geologists were certain that the data correlated perfectly with the then-reigning model of stationary continents. ![]()
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