| Question |
Answer |
| fossil | evidence or remains of once-living plants or animals |
| unaltered hard part | a bone or shell that has not undergone change since the organism's death |
| altered hard part | organic material is replaced with minerals |
| petrified | turned to stone |
| mold | impression left by an organism - a leaf or shell for example |
| cast | mold is filled with minerals |
| index fossil | used to correlate rock layers; easily recognized, abundant, and widespread geographically |
| trace fossil | indirect evidence of life, like a footprint |
| stratigraphy | the study of rock layers and the fossils they contain |
| uniformitarianism | forces and processes that we observe today have been at work for a very long time |
| original horizontality | sediments are laid down in horizontal layers |
| superposition | in undisturbed bedrock, the oldest rocks are at the bottom and the youngest rocks are on the top |
| cross-cutting relationship | intrusion, folding, or fault is younger than the rock it cuts across |
| unconformity | buried surface of erosion |
| relative age | puts the age of materials in order; puts events in a sequence |
| absolute age | gives the actual age of a material |
| isotope | atom that has a different number of neutrons in its nucleus than normal |
| half life | the amount of time it takes for half the parent material to decay to daughter material |
| parent material | the original, unstable isotope |
| daughter material | the stable isotope that results from radioactive decay |
| radioactive decay | spontaneous breakdown of nuclei of unstable isotopes |
| radiometric dating | using the process of radioactive decay to find the absolute date of a material |
| radiocarbon dating | finding the absolute age of a once-living organism using the carbon 14 decay process |
| dendrochronology | tree ring dating |
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