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3. A long cylinder of ice obtained from drilling through ice caps or ice sheets
6. The scientific study of origin, history, and structure of earth and the processes that shapes the earth
7. The trace or remain of an organisms 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 radio active decay to form a daughter isotope
10. The weather conditions in an area over a long period of time
12. Method of determining whether an event or object is older or younger than other events or objects
13. A principal that states that younger rock lie above older rock if the layer have been not disturbed
14. A fossilized structures, such as a footprint of a coprolite, the form in sedimentary rock by animal activated on or within soft sediment
15. An ordered arrangement rock layers that is based on relative ages of the and in which the oldest rock are at the bottom

1. A break im the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
2. A principal that geologic process that occurred in the past can be explained by current geologic processes
4. The standard method used to divide earths long natural history into managenle parts
5. Any method of measuring the age of an event ir 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 determining the absolute age of an of object by comparing the relative percentages if a radctive (parent) isotope and a stable (daughter) isotope