Earth's Early History

Planetary Accretion

4550 BCE

Approximately 4.6 billion years ago, Earth was formed from planetary accretion. Planetary accretion is when large clumps of rocks and matter to join together, creating an accretion disk (artist's concept below). The center of gravity eventually causes the large clumps to join and collapse on each other. The lighter elements such as hydrogen and helium get "blown away" by solar wind. This gives us terrestrial planets, while planets further away with less solar wind tend to be gas giants.

Core Formation

4549 BCE

Due to the fact that denser materials tend to sink, this is exactly what happened to the Earth. Molten iron flowed to the core while lighter elements tend to stay in the upper mantle or crust. This is why each layer of the Earth is different from each other, similar when oil is mixed with water.

Formation of the Moon

4527 BCE

The Moon's creation was much different compared to the other planets in the solar system. A Mars-sized asteroid impacted the Earth, causing it to eject a portion of its mantle. The ejected mass formed a ring around Earth, then the debris slowly clumped together to form the Moon we know today. Scientists were able to predict this due to radiometric dating, material composition, and isotopic signatures.

Late Heavy Bombardment

3800 BCE

The End of the LHB marked the of the Hadean eon and brought upon the Archean eon. The terrestrial planets were frequently bombarded by asteroids and meteorites, making it unable to cool. After stabilization of asteroid orbits (mainly the Asteroid belt), the heavy bombardment stopped. However, this doesn't prevent future asteroid bombardments, especially if there are other interferences that may disrupt orbit.

Planetary Cooling

3799 BCE

After the end of LHB, the planet could start to slowly cool off, creating oceans and making life possible.