The colours depicting the continental crustal geology shown on each of the small Earth models represent rocks that were formed during the five major intervals of geological time, including the most ancient Archaean Eon—beginning around 4,000 million years ago—followed by the Proterozoic Eon and then the Palaeozoic, Mesozoic, and Cenozoic Eras. Similarly, the colours depicting the seafloor crustal geology represent rocks that were formed during the geological time periods and epochs, ranging from the Jurassic—beginning around 200 million years ago—through to present-day times, plus one model extrapolated to 5 million years into the future. For the actual age relationships of these geological times refer to the "International Chronostratigraphic Chart" available using this link.