Chapter 9 Vocab

An ordered arrangement of rock layers.

Eons divided into smaller units of time.

Eras divided into smaller units of time.

Period divided into smaller units of time. The smallest unit of time.

Gradual development of new organisms from preexisting organisms.

The time interval that began with the formation of Earth and ended about 542 million years ago.

Geologic Era that began about 542 million years ago and ended about 251 million years ago.

Episode which an enormous number of species died.

Geologic Era that began about 251 million years ago and ended about 65 million years ago.

Division of geologic time that began about 65 million years ago and that includes the present period.