Precambrian Time

of the Earth

The Precambrian, dating 4600-544 mya, marks the part of Earth's history from its formation to the beginning of life. Precambrian Time is considered an eon.

This eon makes up 85% of the Earth's history! It is split into 3 eras: Hadean, Archaean, and Proterozoic.

The beginning of this era is thought to have had considerable volcanic activity and frequent meteor showers.

As the Earth cooled, it developed its initial atmosphere. Even though it contained no oxygen, the first life forms, prokaryotes, began to develop. From their interaction with the then carbon dioxide and sulfur rich atmosphere, they slowly altered, developing into the first eukaryotes. These organisms than began to produce oxygen.

As the atmosphere slowly became enriched in oxygen, complex multicellular organisms evolved, as well as the development of the ozone layer. This prevented radiation from hitting Earth, allowing the emergence of new life forms.

The abundance of all these new life forms is known as the Precambrian Explosion. This was the end of the epoch, and the beginning of the Paleozoic era.

Hadean (4600 - 3800 mya)
Archaean (3800 - 2500 mya)
Proterozoic (2500 - 543 mya)