Across
- 2. the current geologic era, which began 65.5 million years ago; also called the Age of Mammals
- 4. an ordered arrangement of rock layers that's based on the relative ages of the rocks & in which the oldest rocks are at the bottom
- 7. an episode during which large numbers of species become extinct
- 9. a subdivision of geologic time that's longer than an age but shorter than a period
- 10. a unit of geologic time that's longer than an epoch but shorter than an era
Down
- 1. the geologic era that followed Precambrian time & that lasted from 542 million to 251 million years ago
- 3. the interval of time in the geologic time scale from Earth's formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million years ago
- 5. a unit of geologic time that includes 2 or more periods
- 6. the geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles
- 8. a heritable change in the characteristics within a population from 1 generation to the next; the development of new types of organisms from preexisting types of organisms over time