Precambrian

The Precambrian is the earliest part of Earth's history, spanning from the formation of the Earth about 4.6 billion years ago to the beginning of the Cambrian period, approximately 541 million years ago. It is divided into three eons: the Hadean, Archean, and Proterozoic eons.

Hadean Eon

The Hadean eon began with the formation of the Earth and ended around 4 billion years ago. During this time, the Earth was subjected to intense bombardment by meteors and comets, and the surface was molten due to high temperatures.

Archean Eon

The Archean eon followed the Hadean eon and lasted until about 2.5 billion years ago. During this eon, the Earth's crust solidified, continents began to form, and the first signs of life appeared in the form of single-celled organisms like bacteria and archaea.

Proterozoic Eon

The Proterozoic eon spanned from about 2.5 billion years ago to the beginning of the Cambrian period. It is characterized by the formation of more complex life forms, including multicellular organisms, as well as the development of oxygen in the atmosphere due to photosynthetic bacteria.

Study Guide

1. What are the three eons of the Precambrian?
2. Describe the characteristics of the Hadean eon.
3. What significant events occurred during the Archean eon?
4. How did life evolve during the Proterozoic eon?
5. What were the major environmental changes that took place during the Precambrian?