A theory stating that the Earth's continents have been joined together and have moved away from each other at different times in the Earth's history.
Alfred Wegener proposed the theory of continental drift at the beginning of the 20th century. His idea was that the Earth's continents were once joined together, but gradually moved apart over millions of years. It offered an explanation of the existence of similar fossils and rocks on continents that are far apart from each other.
However evidence from biogeographic and oceanographic studies and the emergence of plate tectonics theory has established its validity.

It took a long time for the idea to become accepted by other scientists.
It is thought that the original landmass, Pangaea, broke up in the Mesozoic into Gondwana (or Gondwanaland) and Laurasia. The subsequent break-up of Gondwana resulted in the formation of the landmasses of the southern hemisphere, i.e. Africa, India, South America, Australia, Antarctica, and New Zealand, while the break-up of Laurasia gave rise to North America and Eurasia. The theory helps to explain the present disjunct distributions of certain plant and animal groups.