Hadean Eon

The Hadean Eon is the earliest geological period of Earth, beginning about 4.6 billion years ago and lasting until around 4.0–3.8 billion years ago. It is named after Hades from Greek mythology, reflecting the extreme and hostile conditions of early Earth. There are almost no preserved rocks from this time, so our knowledge comes mainly from meteorites and ancient zircon crystals. During this eon, Earth’s internal layers—core, mantle, and crust—were largely formed.