A supercontinent is a landmass comprising a large fraction of the entire continental crust. It is the product of the assembly of many smaller continents into one single continent. Supercontinents form in cycles, coming together and breaking apart about every 500 million years as a result of plate tectonic movements. Examples include Rodinia (from 1,100 to 750 Ma) and Pangea (between 300 and 200 Ma). The latter split apart between 200 and 180 Ma ago to form two smaller supercontinents, Laurasia and Gondwana. The oldest putative supercontinent is Vaalbara (3.1–2.5 Ga) which regrouped ancient Archean terranes of the Pilbara Craton (Western Australia) and the Kaapvaal Craton (South Africa).