Module 7 Geologic Time Terms PDF

aModule Vocabulary Geologic Time Term Definition uniformitarianism a principle stating that geologic processes that occur today are similar to those th...

aModule Vocabulary Geologic Time Term Definition uniformitarianism a principle stating that geologic processes that occur today are similar to those that occurred in the past. absolute age the numerical age, in years, of a rock or object. relative age the age of rocks and geologic features compared with other nearby rocks and features. superposition the principle that in undisturbed rock layers, the oldest rocks are on the bottom. original horizontality principle that most rock-forming materials are deposited in horizontal layers. lateral continuity principle that sediments are deposited in large, continuous sheets in all lateral directions. inclusions a piece of an older rock that becomes a part of a new rock. cross-cutting the principle that if one geologic feature cuts across another relationships feature, the feature that it cuts across is older. fossils the preserved remains or evidence of past living organisms. mass extinctions the extinction of many species on Earth within a short period of time. unconformities surfaces where rock has eroded away, producing a break, or gap, in the rock record. correlation a method used by geologists to fill in the missing gaps in an area’s rock record by matching rocks and fossils from separate locations. index fossils a fossil representative of a species that existed on Earth for a short length of time, was abundant, and inhabited many locations. key bed a rock or sediment layer with distinctive characteristics that make it easily identifiable in correlation. geologic time scale a chart that divides Earth’s history into different time units based on changes in the rocks and fossils