Across
- 3. a principle that geologic processes that occurred in the past can be explained by current geologic processes
- 5. the weather conditions in an area over a long period of time
- 7. the scientific study of the origin, history, and structure of Earth and the processes that shape Earth
- 10. a principle that states that younger rocks lie above older rocks if the layers have not been disturbed
- 12. the standard method used to divide Earth's long natural history into manageable parts
- 13. a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
Down
- 1. the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
- 2. the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope
- 4. any method of determining whether an event or object is older or younger than other events or objects
- 6. any method of measuring the age of an event or object in years
- 8. an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom
- 9. the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
- 11. a long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates