Across
- 4. dating any method of measuring the age of an event or object in years Radioactive decay the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
- 6. the trace or remains of an organism that lived long ago, most commonly preserved in sedimentary rock Ice core a long cycling of ice obtained from drilling through ice caps or ice sheets, used to study past climate.
- 8. a principle that geologic process that occurred in the past can be explained by current geologic processes.
- 9. time scale the standard method used to divide Earth's long natural history into manageable parts.
- 11. the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope.
Down
- 1. dating a method of determining the absolute age of an object a method of determining the absolute age of an object by comparing the relative percentage of a radioactive (parent) isotope and a stable (daughter) isotope.
- 2. a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time.
- 3. a principle that states that younger rocks lie above older rocks if the layers have not been distributed.
- 5. the weather conditions in an area over a long period of time
- 7. fossil a fossilized structure, such as a footprint or a coprolite, that formed in sedimentary rock by an animal activity on or within soft sediment. Relative dating any method of determining whether an event or object is older or younger than other events or objects.
- 9. column an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom.
- 10. the scientific study of the origin, history, and structure of Earth and the process that shape Earth.