Plate tectonics
Plate tectonics in geology is a scientific theory which explains earth's continents and oceans based on movements of distinct "plates" of the crustal layer of the earth. It can account for both surface and undersea features such as mountain ranges and deep-sea trenches. As such it is a theory broad in scope and rooted in fundamental physical principles, explaining many geological features previously only understood piecemeal using ad hoc hypotheses.
Conventionally the earth has 3 major layers: crust - the outermost layer, mantle and core. Until the early 1960s, with the exception of a very few people such as Alfred Wegener and Arthur Holmes, most scientists believed the continents and seas to be largely unchanged. It was believed "local" crustal movement formed mountain ranges, understood by the geosyncline concept which had been elaborated in the latter 19th century.
Arguments for an early "super-continent" which split apart over eons were put forward by Alfred Wegener, a German physicist born in 1880, in his book Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans - first edition 1915). His theory was based on several significant coincidences which, taken together, convinced him that the continents had split apart from an enormous land mass he called Pangaea (translated: whole earth), which he believed existed millions of years in the past. Among the coincidences he was trying to explain was the way the shapes of continents seemed to fit together, for example Africa to South America.
Wegener elaborated the theory of continental drift, which assumed that the continents 'plowed' through the oceans, and can be considered a precursor to modern plate tectonics. ..