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Unit 7 vocabulary
Unit 8 vocabulary
| Term | Definition |
|---|---|
| uniformitarianism | A principle that geologic processes that occurred in the past can be explained by current geologic processes. |
| fossil | The trace or remains of an organism that lived long ago most commonly preserved in sedimentary rock. |
| trace fossil | A fossilized structure, such as a footprint or a coprolite, that formed in sedimentary rock by animal activity on or within soft sediment. |
| climate | The weather conditions in an area over a long period of time. |
| ice core | A long cylinder of ice obtained from drilling through ice caps or ice caps or ice sheets; used to study past climates. |
| relative dating | Any method of determining whether an event or object is older or younger than other events or objects. |
| superposition | A principle that states that younger rocks lie above older rocks if the layers have not been disturbed. |
| unconformity | A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time. |
| geologic column | An ordered arrangement of rock layers that is based on the relative ages of the rocks and in which relative ages of the rocks and in which the oldest rocks are at the bottom. |
| absolute dating | Any method of measuring the age of an event or objects 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. |
| half-life | The time required for half of a sample of a radioactive decay to form a daughter isotope. |
| radiometric dating | A method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope. and a daughter isotope |