Science Vocab

2. The standard methods used to divide Earth’s long natural history into manageable parts
6. A break in a geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
8. An ordered arrangement of rock layers that is based on the relative ages of rocks and in which the oldest rocks are at the bottom
12. The process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
13. A fossilized structure, such as a footprint or coprolite, that formed in sedimentary rock by animal activity on or within soft sediment
14. A method of determining absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope.
15. Any method of measuring the age of an event or object in years

1. The weather conditions in an area over a long period of time
3. The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock
4. The scientific study of the origin, history, and structure of Earth and the processes that shape Earth
5. A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates
7. A principle that geologic processes that occurred in the past can be explained by current geologic processes.
9. A principle that states younger rocks lie above older rocks if the layers have not been distrubed.
10. Any method of determining whether an event object is older or younger than other events or objects.
11. The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope.