Across
- 2. life The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope
- 7. time scale The standard method used to divide earths long natural history into manageable parts
- 8. A principal the geologic processes that occurred in the past can be explained by current geologic processes
- 9. The scientific study of the origin, history and structure of Earth and the processes that shape Earth
- 10. dating A method of determining the absolute age of an object by comparing the relative percentages of a radioactive isotope and a stable isotope
- 12. A principal that states that younger rocks lie above older rocks if the layers have not been disturbed
- 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 weather conditions in an area over a long period of time
- 3. dating Any method of determining weather an event or object is older or younger than other event or objects
- 4. The trace or remains of an organism that lived long ago
- 5. core A long cylinder of ice obtained from drilling through ice caps or ice sheets
- 6. dating Any method of measuring the age of event or object in years
- 9. column An ordered arrangement or rock layers that is based on relative aged of the rocks and in which the oldest rocks are at the bottom
- 10. decay The process in which a radioactive isotspe tends to break down into a stable isotope of the smae element or another element
- 11. fossils A fossilized structure such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment