Across
- 2. Period in Earth's history
- 5. A major division of geologic time
- 7. Oldest era; organisms developed hard parts
- 8. Largest extinction in Earth's history
- 10. Formation of oceans, atmosphere, and continents; bacteria
- 11. period characterized by the greatest development, rise of modern insects and flowering plants
- 12. Prehistoric period during which stone was widely used
Down
- 1. record of earths history
- 3. Numerous fishes, other sea life; many plants, first trees; wingless insects
- 4. oldest and longest geologic time period
- 6. a cold-blooded vertebrate including snakes and lizards
- 9. Numerous fishes, other sea life; many plants, first trees; wingless insects