absolute age
The calculated age of an artifact from a specific dating method that is used to determine when the artifact was made
carbon film
a type of fossil consisting of an extremely thin coating of carbon on rock
cast
mineral-rich water or other sediment fills a cavity and forms new rock which produces a copy of the original object
fossil
the remains, imprints, or traces of a plant or animal that existed in a past geological age
half-life
length of time required for half of the radioactive atoms in a sample to decay
index fossil
a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
mold
a cavity into which liquid is poured to create a given shape when it hardens
permineralized remains
fossils in which the spaces inside are filled with minerals from groundwater
principle of superposition
the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest
radioactive decay
the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element.
radiometric dating
A method paleontologists use for determining the ages of rocks and fossils on a scale of absolute time, based on the half-life of radioactive isotopes.
relative age
the age of an object in relation to the ages of other objects
unconformity
a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time
uniformitarianism
principle that Earth's processes occurring today are similar to those that occurred in the past