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Earth's History
| Term | Definition |
|---|---|
| uniformitarianism | A principle of geologic processes that occurred in the past can be explained by current geologic processes |
| fossil | A trace that 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 obtained from drilling through ice caps or ice sheets used to study past climates |
| relative dating | any method or 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 in the layers have not been disturbed |
| unconformity | a break in geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time |
| geologic column | an ordered arangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom |
| `absolute dating | ant method of measuring the age of an event or object in years |
| radioactive dating | the process in which a radioactive istope tends to break down into a stable istope of the same element or another element |
| half-life | the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter istope |
| radiometric dating | a method of determining the absolute age of and abject by comparing the relative percentages of radioactive parent isotope and a stable daughter isotope |