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Unit 5 Fossils
| Term | Definition |
|---|---|
| Rocks | Provide clues to Earth's past |
| Fossils | preserved remains or evidence of ancient living organisms |
| catastrophism | the idea that conditions and creatures on Earth change because of quick, violent events |
| uniformitarianism | the same geologic processes that occur today occurred in the past |
| cast | when a mold fills with sediment or mineral deposits |
| paleontologists | scientists who study fossils |
| superposition | oldest rocks are on bottom when rock layers are undisturbed |
| original horizontality | rock layers might tilt, but they were first deposited horizontally |
| lateral continuity | layers are deposited in continuous sheets in all directions until they thin out or hit a barrier |
| unconformity | surface where rock has eroded away, producing a break, or gap in rock record |
| cross-cutting relations | younger geologic features cut across older geologic features |
| correlation | matching rocks and fossils from separate locations |
| inclusions | pieces of older rock becomes part of new rock |
| index fossils | represent species existed on Earth for a short time, where abundant and inhabited many locations |
| relative age | tells us how old something is compared to another thing or which came first |
| absolute age | tells us how old in years something is |
| law of superposition | states that rock layers are laid down in order from oldest to newest |
| extrusion | lava that hardens on the surface |
| half-life | the amount of time it takes for half of the unstable atoms in a sample to decay |
| isotope | atoms of an element that contains different number of NEUTRONS |