Hadean

4.6 - 4.0 billion years ago - The Hadean Eon represents the earliest chapter of Earth's history, beginning with the planet’s formation around 4.6 billion years ago and ending 4.0 billion years ago. Named after Hades, the Greek underworld, this informal eon describes a hellish, chaotic, and volatile world. Earth was initially a molten sphere of magma generated by frequent collisions with planetesimals and intense radioactive decay. During this time, a Mars-sized body collided with Earth, ejecting debris that eventually coalesced to form the Moon. As the outer crust slowly cooled and solidified, volcanic outgassing released steam and gases, creating a primitive, oxygen-free atmosphere. Eventually, surface temperatures dropped enough for water vapor to condense, resulting in torrential rains that formed the very first oceans. No rocks survive from this eon, leaving only ancient zircon crystals to verify its turbulent history.