Across
- 3. matching of rock outcrops or fossils exposed in one geographic region to similar outcrops or fossils exposed in other geographic regions
- 5. largest unit of time and encompasses the others
- 9. is the principle that sedimentary rocks are deposited in horizontal or nearly horizontal layers
- 11. many groups of organisms disappear from the rock record at about the same time
- 12. states that fragments, called inclusions,in a rock layer must be older than the rock layer that contains them
- 13. what eras are divided into, are generally tens of millions of years in duration
- 15. the principle that in an undisturbed rock sequence, the oldest rocks are at the bottom and each consecutive layer is younger than the layer beneath it
- 16. a rock or sediment layer used as a time marker in the rock record
Down
- 1. states that geologic processes occurring today have been occurring since Earth formed
- 2. states that an intrusion is younger than the rock it cuts across
- 4. a record of Earth's history from it origin 4.6 billion years ago
- 6. buried surfaces of erosion
- 7. what periods are divided into, generally hundreds of thousands to millions of years in duration
- 8. what eons are divided into, are usually tens to hundreds of millions of years in duration
- 10. three earliest eons make up 90% of geologic time, Earth was formed and became hospitable to life
- 14. establishing the order of past geologic events