Across
- 6. this eon was 242 million years ago to the present time
- 7. is a person who studies fossils
- 8. in this time period the Earths continents began to drift together making giant land masses called Pangaeu
- 9. a unit of geologic time that includes two or more periods
- 11. this made the extinction of the dinosaurs
- 12. exists between tow horizontal rock layers and rock layers that are tilted or folded
- 16. this time period was the evolution of mammals
- 18. the largest division of geologic time
- 19. the death of every member of a species
- 22. this is a place where Hutton observed results of a geologic processes that would lead him to form his principle or uniformitarianism
- 23. the standard method used to divide the Earth's long natural history into manageable
- 26. in this time period the Earths landscape began to turn green
- 29. a type of fossil that forms when sediments fill in the cavity left from a decomposed organism
Down
- 1. this person was a 20th-century vertebrate paleontologist who made important contributions to the study of dinosaurs
- 2. a principle that states that geologic change occurs suddenly
- 3. this eon was around 4.6 billion years ago to 3.8 billion years ago
- 4. any method of determining whether an event or object is older or younger than other events or objects
- 5. a subdivision of a geologic time period
- 6. this process in which minerals replace an organism's tissues
- 8. this eon was around 2.5 billion years ago to 542 million years ago
- 10. a mark or cavity made in a sedimentary surface by a shell or other body
- 13. a principle that states that geologic processes that occurred in the past can be explained by current geological processes
- 14. these are the traces or remains of a living organism that died a long time ago
- 15. what time period did the dinosaurs dominate the Earth
- 17. this exists where sedimentary rock layers lie on top of an eroded surface of nonlayered igneous or metamorphic rock
- 20. this exists where part of a sequence of a parallel rock layers is missing
- 21. the time needed for half of a sample of a radioactive substance to undergo radioactive decay
- 24. this burial mound at this place resembles the features of a snake
- 25. a fossilized mark that is formed in a soft sediment by the movement of an animal
- 27. this eon was around 3.8 billion years ago to 2.5 billion years ago
- 28. photos are like a __________ the younger ones lie above and the older ones lie underneath