The document describes the layers of the Earth from the crust on the outside to the inner core on the inside. It then discusses continental drift theory proposed by Alfred Wegener in 1912, which suggested that the continents were once joined together in a supercontinent called Pangaea approximately 200 million years ago and have been slowly drifting apart ever since at a rate of about 2.5 cm per year, forming the seven continents seen today. Wegener provided five pieces of evidence to support this idea: the matching shapes of continental coastlines, similar fossil records, matching rock types, corresponding mountain ranges, and glacial marks pointing in unexpected directions.