January 6, 1912. Alexander Wegener publishes theory of continental drift.
Alfred Wegener first thought of this idea by noticing that the different large landmasses of the Earth almost fit together like a jigsaw puzzle. The Continental shelf of the Americas fit closely to Africa and Europe, and Antarctica, Australia, India and Madagascar fitted next to the tip of Southern Africa. But Wegener only took action after reading a paper in 1911 and seeing that a flooded land-bridge contradicts isostasy. Wegener's main interest was meteorology, and he wanted to join the Denmark-Greenland expedition scheduled for mid-1912. He presented his Continental Drift hypothesis on 6 January 1912. He analyzed both sides of the Atlantic Ocean for rock type, geological structures and fossils. He noticed that there was a significant similarity between matching sides of the continents, especially in fossil plants.
https://en.wikipedia.org/wiki/Alfred_Wegener
