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The concept of plate tectonics has evolved over a long period. Early geological ideas were qualitative and speculative and were not widely accepted, but geophysical data obtained from the ocean floor more recently led to the construction of a quantitative model that has since emerged as the main conceptual framework for the Earth sciences.
The ideas of continental drift, seafloor spreading, and plate tectonics developed sequentially.  The first major protagonist of continental drift was Alfred Wegener, who suggested as early as 1912 that one supercontinent, called Pangea, had broken up during the early Mesozoic and that the separate continents had then drifted to their present positions. He collated evidence to support his theory, such as the similarity of fossil fauna and flora in different continents and the continuity of geological structures and paleoclimatic belts.
Similar geological correlations between South America and Africa were advanced (1927 and 1937) by Alexander L. du Toit, who suggested the existence of two supercontinents--Laurasia in the north and Gondwanaland in the south--separated by the Tethys Sea. In 1929, Arthur Holmes envisaged that subcrustal convection currents were dragging two continents apart with consequent mountain building at the margin of a trench. Apparent confirmation of continental drift came in 1956 when Stanley Keith Runcorn and his colleagues established that the polar-wandering paths for North America and Europe diverge progressively from the present to the Triassic.
Beginning in the late 1950s, oceanographers began to discover magnetic anomaly stripes in the ocean floor; their significance, however, was not initially understood. The first major breakthrough came in 1960 when H. H. Hess suggested that new ocean floor was created at the mid-oceanic ridges and that the ocean evolved by seafloor spreading. The second came in 1963, when D. H. Matthews, F. J. Vine, and Lawrence Whitaker Morley proposed that the alternating magnetic anomalies in the ocean floor were caused by regular reversals in the Earth's magnetic field. Such geomagnetic reversals were previously known only in continental rocks. A further advance came in 1965 when J. Tuzo Wilson advocated the transform-fault mechanism to explain how oceanic plates slide laterally past each other.
The concept of plate tectonics came to fruition by 1970. The tectonic plates of the world were tentatively defined, along with their relative directions of movement and the rates of extension and compression at their boundaries. Major earthquake zones were correlated with the boundaries, and schematic models were developed the evolution of island arcs, Cordilleran mountain belts, and Himalayan belts. The foundations of such mountain building were located at subducting and collisional plate boundaries. It is increasingly accepted that plate tectonic processes have been responsible for the growth of the earth's continents since the beginning of geologic time about 4 billion years ago.
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