| Term | Definition |
|---|
| fossils | evidence such as the remains, imprints, or traces of once living organisms preserved in rocks |
| petrified remains | hard and rocklike |
| carbonaceous film | fossil impression in rock, consisting only a thin carbon residue that forms an outline of the original organism |
| mold | cavity in rock that has the shape of a fossil that was trapped there;water dissolved the fossil away leaving its imprint |
| cast | type of fossil formed when an earlier fossil in the rock is dissolved away leaving behind the impression of that fossil, and new sediments or mineral crystals fill the mold |
| index fossils | a fossil of a species that was abundant, existed briefly, and was widespread geographically' used in determining the relative age of rock layers |
| extinction | no longer has any living members |
| principle of superposition | states that in an undisturbed layer of rock, the oldest rocks are on the bottom and the rocks become progressively younger toward the top |
| relative dating | used in geology to determine the order of events and the relative age of rocks by examining the position of rocks in a sequence |
| unconformity | gap in rock layers |
| absolute dating | method used by geologists to determine the age of a rock or other object |
| radioactive decay | decay of an atom of one element to form another element, occuring when an alpha particle or beta particle is expelled from the original atom |
| half-life | time it takes for half of the atoms in the isotope to decay |
| radiometric dating | process of measuring the amounts of parent and daughter materials in a rock and by knowing the half-life of the parent, a geologist can calculate the absolute age of the rock |
| uniformitarianism | states that Earth processes occuring today are similiar to those that occured in the past |
| trace fossils | fossilized tracks and other evidence of animal activity |
| original remains | when actual or part of an organism is found |
Combine with other sets
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