Hadean Eon

Definition: The Hadean Eon (4500 to 3800 MYA) is the earliest of all time periods recognized in the history of Earth. During the Hadean Eon, the Solar System was still forming. The sun formed and the planets started taking shape. The early Earth consisted of molten rock. As Earth cooled, the molten rock solidified and the geological history of our planet began. The oldest known rocks on earth are 3800 million years old. The end of the Hadean Eon coincides with the formation of solid rock on our planet. The Hadean Eon was followed by the Archaeon Eon.