Hadean Eon

The Hadean eon (4,540 – 4,000 mya) represents the time before a reliable (fossil) record of life.
Temperatures were extremely high, and much of the Earth was molten because of frequent collisionswith other bodies, extreme volcanism and the abundance of short-lived radioactive elements.
A giant impact collision with a planet-sized body named Theia (approximately 4.5 billion years ago) is thought to have formed the Moon.
The moon was subjected to Late Heavy Bombardment(LHB – lunar cataclysm – 4 billion years ago).
During the LHB phase, a disproportionately large number of asteroids are theorised to have collided with the early terrestrial planets in the inner Solar System, including Mercury, Venus, Earth, and Mars.
Volcanic outgassingprobably created the primordial atmosphere and then the ocean.
The early atmosphere contained almost no oxygen.
Over time, the Earth cooled, causing the formation of a solid crust, leaving behind hot volatiles which probably resulted in a heavy CO₂atmosphere with hydrogen and water vapour.
Liquid water oceans existed despite the surface temperature of 230° C because, at an atmospheric pressure of above 27 atmospheres, caused by the heavy CO2 atmosphere, water is still liquid.