Science Vocabulary

2. The process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
5. The standard method used to divide Earth's long natural history into manageable parts.
6. The time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope.
8. A fossilized structure, such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment.
9. A principle that geologic processes that occurred in the past can be explained by current geologic processes.
10. A principle that states that younger rocks lie above older rocks if the layers have not been disturbed.
12. The weather conditions in an area over a long period of time.
13. Any method of measuring the age of an event or object in years.
14. A long cylinder of ice obtained from drilling through ice caps or ice sheets; used to study past climates.
15. The scientific study of the origin, history, and structure of Earth and the processes that shape Earth.

1. Any method of determining whether an event or object is older or younger than other events or objects.
3. The trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock.
4. 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.
7. A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
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.