11.4: The Geologic Time Scale

The whole geologic history of the Earth divided into units of varying magnitude:

These represent the greatest expanses of time on the geologic time scale.

The eon that began 542 million years ago, a term that means visible life.

Eons are divided into these smaller units:

The earliest era within the Phanerozoic eon, meaning ancient life.

The middle era within the Phanerozoic eon is the______________, meaning middle life.

The most recent era within the Phanerozoic, meaning recent life.

Each era can be further divided into:

Each period can be divided still into smaller units called:

The two eons that occurred before the Cambrian together are often referred to as the: