Geological eons, periods and epochs

The timeline below runs from the formation of our planet Earth 4.6 billion years ago (4.6 Bya), to 2 million years ago (2 Mya), at the first appearance of Homo erectus. Its log-scale equally spaces successive intervals in time halfway to the present from the last; for example, 1 Bya lies midway between 2 Bya and 500 Mya. This multiplicative scaling allows the same timeline to visualise earlier periods and manyfold shorter recent periods. For example, the Proterozoic Eon lasted almost 2 billion years, encompassing the earliest multicellular life, the arrival of Eukaryotes and amongst them the Metazoa (animals) including the first bilaterians, before the nearly 4× shorter Phanerozoic Eon, encompassing the last 540 million years from the Cambrian explosion of animal diversity through to the present. Pink arrows point to Phanerozoic mass extinction events. The epochs of our current Quaternary Period are plotted on a separate archaeological timeline here.

C.P. Doncaster, Timeline of the Human Condition, star index