The document discusses early theories of continental drift proposed by Alfred Wegener and evidence that supported his hypothesis. It also describes how Harry Hess contributed to the development of the theory of sea floor spreading, which helped explain continental drift. Hess proposed that new ocean floor forms at mid-ocean ridges due to magma rising from below the crust. Evidence such as matching landforms, fossils, and climates across continents supported the idea that continents move over time.