Early Earth

Early Earth refers to our planet during its first several hundred million years, roughly 4.5 to 4.0 billion years ago. This was a violent, transformative era that set the stage for all life to come.

The young Earth was a hellscape of intense heat and constant bombardment. Planetesimals and asteroids crashed into the surface, generating enough energy to keep the crust molten. The Moon likely formed from a giant impact around 4.5 billion years ago. Gravity and radioactive decay within the planet's interior caused clustering of heavier elements toward the core—a process called planetary differentiation.

As the surface slowly cooled, a solid crust began to form. Water vapor released from the planet's interior and delivered by comets accumulated into the first oceans. An early atmosphere developed, though radically different from today's—rich in nitrogen, carbon dioxide, and methane, with little free oxygen. The young Sun was dimmer, yet greenhouse gases kept the planet warm enough for liquid water.

Within these ancient oceans, the chemistry of life began. Bacteria emerged by around 3.8 billion years ago, fundamentally reshaping Earth's atmosphere and geology over billions of years that followed.

Related

Hadean Eon, Archean Eon, Geological time scale, Origin of life, Plate tectonics, Late Heavy Bombardment