Across
- 2. four billion years ago the fist single celled organisms existed during the _____ periode
- 4. a subdivision of a geologic period
- 6. ______ are four hundred million years old and are also called phacops
- 7. age of the dinosaurs and the first flowering plants
- 10. measuring the age of an event or object in years
- 12. determining weather a object is older or younger than others
- 16. an arrangement of rock layers in which the older rocks are at the bottom
- 22. death of every member of a species
- 24. fossil that is found in only one geologic age
- 25. ______ states that geological processes happen over time
- 26. _______ states that geological processes happen suddenly
- 27. fossilized mark formed in soft sediment
- 28. fossil that forms when mold is filled
- 29. the scientific study of fossils
Down
- 1. ____ _____ created the theory of evolution
- 3. one continent forms called pangaea
- 5. _____ appear 8 million years ago as australopithecus
- 8. life moved on land as fish evolved into tetrapods
- 9. the first uniformitarianism
- 11. a unit of geologic time that includes multiple periods
- 13. the age of the mammals prevails after the dinosaurs go extinct
- 14. largest division of geologic time
- 15. the ice age comes and the first humans appear
- 17. coal that we burn today comes from this once luscious forest
- 18. cavity made in object by shell or other body
- 19. a break in the geologic record created when rock layers are eroded or sediment is not deposited over a long time
- 20. _______ states that younger rocks lie on older rocks
- 21. remains of an organism that lived long ago
- 23. after the precambrian life covered the sea floor
- 29. unit of geologic time into which eras are divided