9. A very brief history of the Earth

Our planet is ancient—at 4.6 billion years—and over that time it has changed enormously. ‘A very brief history of the Earth’ describes how the Earth and Moon were created in the Chaotian Eon from the collision of two planets: Tellus and Theia. It outlines the heavy meteorite bombardment of the Hadean Eon; the Archean Eon (c.3.8 billion years ago) when rocks were first preserved; the arrival of oxygen in Earth’s atmosphere and explosion of organic life in the Proterozoic Eon; and the Phanerozoic Eon, in which we still live. The various eras of this eon are described: the Palaeozoic Era, the Mesozoic Era, and the Cenozoic Era.