Card Set Information
a ordered arrangement of rocks
small units of geologic time.
shorter times of eras
a smaller time frame, smaller than a period
living species that have changed over time.
the time period around the formation of the earth
a time period that started 542 million years ago and ended 251 million years ago
a enormous amount of species die
a time period that started about 251 million years ago and ended 65 million years ago
a time period that started about 65 million years ago and includes this time period.