The Geologic Time Scale
Across
- 2. The meteorite that struck Earth in the Paleogene period caused a change in global _______
- 3. Element found in the K-T boundary that is not prevalent on Earth
- 5. Earth's _________ was 4.6 billion years ago
- 7. Epoch in which humans began to form civilizations
- 10. An event in which many species become extinct in a short time; they occur every 26 to 30 million years on average and are known as mass ___________
- 11. Cause of the mass extinction of the dinosaurs after the Cretaceous period
- 14. Extensive glaciation occured before the______
- 15. By the end of the Carboniferous period, the first ____ began to roam the forests
- 16. Era that means "recent life"
- 17. The appearance of the first mammals
Down
- 1. Number of eras in the Phanerozoic eon
- 2. Groups of organisms rapidly diversified in the _______ explosion
- 4. Birds evolved from ________, who lived in the Mesozoic era
- 6. The land mass that existed on Earth 225 million years ago
- 8. 90 percent of all history
- 9. Largest division divides the scale into ______ parts
- 12. Movement of plate ________ that make up the surface of Earth
- 13. The model that expresses the major geological and biological events in Earth's history is known as the ________ time scale