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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 |