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4600 BCE
Planetary Accretion
The formation of the Earth and the other terrestrial planets of our Solar System (Mercury, Venus and Mars) commenced 4.567 billion years ago and occurred on a time scale of about 100 million years. These planets grew by the process of accretion, which involved numerous collisions with smaller (Moon- to Mars-size) bodies. -
4540 BCE
Outer Core Formation (Earth's Layers)
500 million years after planetary accretion, Earth had a distinct core. Deep in Earth is a ball of iron that is solid and one that is liquid. At first, it was only liquid. The densest liquids got in the middle, thanks to planetary differentiation. Constant activity keeps the outer core in its liquid state and lots of things are still affected by it, such as the magnetic field. -
4530 BCE
Formation of the Moon
Known as Theia, the Mars-sized body collided with Earth, throwing vaporized chunks of the young planet's crust into space. Gravity bound the ejected particles together, creating a moon that is the largest in the solar system in relation to Earth. -
4300 BCE
Planetary Cooling
Every billion years, the Earth gets 100 degrees Celsius cooler. About 3.7 to 4.3 billion years ago was when the Earth became cool enough to be more solid, then various meteors and asteroids formed the Earth into the sphere that it is. -
4100 BCE
End of Heavy Bombardment
The end of the heavy bombardment was 4.1 to 3.8 billion years ago. It was when a large number of asteroids impacted Earth and other terrestrial planets. This is what completed the accretion of the planets into how we see them today.
