Unit 2 Science Vocab

4. The standard method used to divide Earth’s long natural history into manageable parts.
7. The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock.
9. The scientific study of the origin, history, and structure of Earth and the processes that shape Earth.
10. A long cylinder obtained from drilling through ice caps or ice sheets; used to study past climates.
12. 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. 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.

1. The process in which a radioactive isotope tends break down into a stable isotope of the same element or another element.
2. The weather conditions in an area over a long period of time.
3. The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope.
5. An ordered arrangement of of rock layers that is based on the relative ages of the rocks and in which the oldest layers are at the bottom.
6. Any method of measuring the age of an event or object in years.
8. A principle that geologic processes that occurs in the past can be explained by current geologic processes.
11. Any method of determining whether an event or object is older or younger than other event or objects.
13. A break in the geological record created when rock layers are eroded or when sediment is not deposited for a long period of time.