Plate tectonics
Plate tectonics in geology is an attempt to explain the relative movement of large areas of the crustal layer of the earth, including the continents and udersea continental shelf, over long periods of time. 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 large-scale shape of the continents and seas to be unchanging, with the exception of vertical crustal movements which formed mountain ranges. These were understood at the time by the geosyncline concept elaborated in the latter 19th century.
Significant 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 Pangaea (translated: whole earth), a hypothetical enormous land mass which he believed existed millions of years in the past. ..
The theory was not taken seriously until 40 years later, after discoveries such as seafloor spreading.