The ocean floor is a conveyor belt, spreading apart at its own seams

In 1962, geologist Harry Hess proposed that new crust forms at mid-ocean ridges and slowly pushes older seafloor toward the continents, where it's recycled back into the mantle. Seafloor spreading gave Wegener's mocked idea of continental drift an actual mechanism, and helped establish plate tectonics as settled science.

— Harry Hammond Hess, History of Ocean Basins — 1962