puzzle time

3. a drill core of ice that can help tell the climates of the past
6. Study of the earth
7. A trace of an ancient organism that has been preserved in rock.
9. length of time required for half of the radioactive atoms in a sample to decay
10. Overall weather in an area over a long period of time
12. Method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock
13. is a principle that states that younger rocks lie above older rocks if the layers have not been disturbed
14. A type of fossil that provides evidence of the activities of ancient organisms
15. an arrangement of rock layers 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 deposited for a long period of time.
2. A principle that geologic processes that occurred in the past can be explained by current geologic processes
4. scale used by paleontologists to represent evolutionary time
5. A technique used to determine the actual age of a fossil
8. A spontaneous process in which unstable nuclei lose energy by emitting radiation
11. the process of measuring the absolute age of geologic material by measuring the concentrations of radioactive isotopes and their decay products