What discovery led to the theory of plate tectonics?

The beginning of the theory of plate techtonics began about 1920. Alfred Wegener brought it up. In the 1950's, scientists found the align,emt of megnetic particles in rock responded to the earths magnetic field.
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Pangea. Alfred Wegener presented the idea that the continents was once a super large continent, otherwise known as Pangea, and over time broke and drifted apart into their present positions. It didn't brought out worldwide interests till late 1950s when scientists discovered magnetic particles responding to earth's magnetic field. And from then on, other evidence followed. It basically happened because of Wegener's theory of Pangea.