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Chapter 6 Vocab
Vocabulary for Chapter 6
| Question | Answer |
|---|---|
| Uniformitarianism | a principle that geologic processes that occurred in the past can be explained by current geologic processes |
| Catastrophism | a principle that states that geologic change occurs suddenly |
| Paleontology | the scientific study of fossils |
| 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 |
| Geologic 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 |
| 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 |
| Absolute dating | any method of measuring the age of an event or object in years |
| isotope | an atom that has the same number of protons (or the same atomic number) as other atoms of the same element do but that has a different number of neutrons (and thus a different atomic mass) |
| Radioactive decay | the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element |
| Radiometric dating | 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 |
| Half-life | the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope |
| 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 |
| Mold- in biology | a fungus that looks like wool or cotton |
| Cast | a type of fossil that forms when sediments fill in the cavity left by a decomposed organism |
| Index fossil | a fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread and the species that formed that fossil existed for only a short span of geologic time |
| Geologic time scale | the standard method used to divide Earth's long natural history into manageable parts |
| Eon | the largest division of geologic time |
| Era | a unit of geologic time that includes two or more periods |
| Period | in physics, the time that it takes a complete cycle or wave oscillation to occur |
| Epoch | a subdivision of geologic time that is longer than an age but shorter than a period |
| Extinction | the death of every member of a species |
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sousankelsey
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