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