The numerical age, in years, of a rock or object

the age of rocks and geologic features compared with other nearby rocks and features

the principle that in undisturbed rock layers, the oldest rocks are on the bottom

principle that most rock-forming materials are deposited in horizontal layers

principle that sediments are deposited in large, continuous sheets in all lateral directions

a piece of an older rock that becomes a part of a new rock

the principle that if one geologic feature cuts across another feature, the feature that it cuts across is older

the preserved remains or evidence of past living organisms

the extinction of many species on Earth within a short period of time

a surface where rock has eroded away, producing a break, or gap, in the rock record (dis-, angular, or non-)

method used by geologists to fill in the missing gaps in an area's rock record by matching rocks and fossils from separate locations (this work also has a non-science definition that is similar)

a fossil representative of a species that existed on Earth for a short length of time, was abundant, and inhabited many locations

a rock or sediment layer with distinctive characteristics that make it easily identifiable in correlation

a chart that divides Earth’s history into different time units based on changes in the rocks and fossils