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1 CE
Core formation
The core is Earth's deepest layer. It is a ball of solid iron just larger than Pluto which is surrounded by a liquid outer core. -
3
End of heavy bombardment 3.8 billion
During this interval, a disproportionately large number of asteroids are theorized to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars. -
4
Planetary accretion 4.3 billion
The earth grew from the accumulation of planetismals (meteorites and asteroids) over a period of 1-200 million years -
4
Planetary cooling
By 4 billion years ago the earth had cooled enough for the outer layers to have solidified and for oceans to form. -
4
Formation of the moon 4.5 billion
Perhaps Earth's gravity snagged a passing body.