What are the major eras of earth's history?
Precambrian (the oldest), Paleozoic, Mesozoic and Cenozoic (most recent)
There are 4 eras.
The oldest, the Precambrian Era, began with the formation of the Earth 4.6 billion years ago. The Precambrian Era accounts for 88% of Earth's history. This was followed by the Paleozoic Era (600 to 225 million years ago) and the Mesozoic Era (225-65 million years ago). The current, the Cenozoic Era, began 65 million years ago.