What hypothesis suggests that continents were once a single landmass?

The hypothesis that continents were once a single landmass is known as continental drift. This idea, first proposed by Alfred Wegener in the early 20th century, suggests that all continents were once joined together in a supercontinent called Pangaea. Over millions of years, Pangaea broke apart, and the fragments drifted to their current locations.

Continental drift provides a framework for understanding the movement of continents over geological time scales. It explains the fit of continental outlines, similarities in fossil records across continents, and geological features such as mountain ranges and coal deposits found in areas now separated by oceans. This hypothesis set the stage for the development of the modern theory of plate tectonics, which expanded on Wegener's ideas by providing the mechanism for the movement of the continents through tectonic plates on the Earth's surface.