| A | B |
|---|
| uniformitarianism | the theory that geologic processes have been occuring since Earth formed |
| relative age dating | establishing the order of past geologic events |
| original horizontality | principle that sedimentary rocks are deposted in nearly horizontal layers |
| superposition | principle that in an undisturbed rock sequence, the oldest are on the bottom and each layer is younger than the one beneath it |
| cross-cutting relationship | principle that an intrusion is younger than the rock it cuts across |
| principle of inclusions | principle that fragments called inclusions in a rock layer must be older than the rock layer containing them |
| unconformity | gap in the rock record caused by erosion or weathering |
| correlation | matching of rock outcrops of one geogrraphic region to another |
| key bed | a rock or sediment layer that serves as a time marker |
| absolute age dating | method that enables scientists to determine the actual age or rocks |
| radioactive decay | emission of radioactive particles and resulting change into other isotopes over time |
| radiometric dating | process used to determine the absolute age of a rock or fossil by parent nuclei to daughter nuclei |
| half life | period of time it takes for a radioactive isotope to decay to 1/2 its original amount |
| radiocarbon dating | determines the age of relatively young organic objects |
| dendrochronology | science of using three rings to determine absolute age |
| Varve | alternating light-colored and dark-colored sedmintary layer of sand, clay, and silt |
