new vocab

3. a long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates
6. the scientific study of the origin, history, and structure of earth and the processes
7. the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
9. the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope
10. the weather conditions in an area over a long period of time
12. any method of determining whether an event object is older or younger than other events or objects
13. a principle that states that younger rocks lie above older rocks if the layers have not been disturbed
14. a fossilized structure, such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment
15. 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

1. a break in the geologic record created when rock layers are eroded or when sediment is not deposed for a long period of time
2. a principle that geologic process that occurred in the past can be explained by current geologic process
4. the standard method used to divide earth's long natural history into manageable parts
5. any method of measuring the age of an event or object in years
8. the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
11. 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