Across
- 2. A break in the geological record created when rock layers are eroded or when sediment is not deposited for a long period of time
- 3. A fossilized structure that formed in sedimentary rock by animal activity
- 4. The process in which radioactive isotopes tends to break down into a stable isotope of the same element or another element
- 5. Any method of measuring the age of an event or object in years
- 7. A long cylinder of ice obtained by drilling through ice caps used to study past climates
- 8. The scientific study of origin, history, and the structure of earth and the processes that shape earth
- 10. The trace remains of an organism usually preserved in sedimentary rock
- 11. The weather conditions over a long period of time
- 12. Any method of determining whether an event or object is older or younger than other events or objects
- 14. The standard method used to divide earth's long natural history into manageable parts
- 15. An ordered arrangement of rock layers that is based on the relative ages of the rocks in which the oldest rocks are at the bottom
Down
- 1. A method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope
- 6. Geological processes in past are explained by current geological processes
- 9. A principle that states younger rocks lie above older rocks if the layers have not been distributed
- 13. The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope