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7 CK Earth history
7th CK SCI - HISTORY OF EARTH, FOSSILS - COMPLETE #1
Term | Definition |
---|---|
Absolute age | how old a layer is in terms of actual years |
Angular unconformity | the beds below the surface were deformed prior to deposition of the overlaying strata |
Disconformities | a gap between parallel layers in the rock record |
Fossils | the remains or traces of plants and animals that lived in the past |
Half-life | the amount of time that it takes for half of the unstable element to become a more stable element |
Index fossil | A widely distributed fossil that contains an organism that lived briefly. |
Isotope | an element that occurs in several different forms |
Non-conformity | exists when metamorphic or igneous rocks are overlaid by sedimentary rocks |
Paleontology | a science dealing with the life of past geological periods as known from fossil remains |
Principle of cross-cutting relations | any geologic features is younger than anything else it cuts across |
Principle of Superposition | younger rocks are deposited on top of older rocks |
Principle of Uniformitarianism | the process that occurred in the past times produced the same results as similar processes do today |
Radioactive decay | unstable isotopes change into more stable forms |
Relative age | how old one layer is in relation to another layer |
Trace fossils | evidence that these organisms once roamed the planet |
Unconformity | lack of continuity in deposition between rock strata in contact corresponding to non-deposition weathering or erosion |
Uniform | having always the same form, manner or degree; not varying |