Earth History Vocab 1. relative age 7. mold 13. period 2. superposition 8. cast 14. epoch 3. Inclusion 9. absolute age 15. Paleozoic Era 4. unconformity 10. eon 16. Mesozoic Era 5. index fossil 11. era 17. Cenozoic Era 6. catastrophism 12. uniformitarianism relative age age of rocks and geologic features compared with other nearby rocks and features. superposition Principle that in undisturbed rock layers position the oldest rocks on the bottom, the newer rocks on the top inclusion piece of an older rock the that becomes a part of a new rock unconformity Surface where rock has eroded away, producing a break, or gap, in the rock record index fossil represent species that existed on Earth for a short length of time, were abundant, and inhabited ,amy locations. catastrophism idea that conditions and organisms on Earth change in quick, violent events mold impression of an organism in a rock cast fossil copy of an organism in a rock absolute age numerical age, in years, of a rock or object eon longest unit of geologic time 4. Phanerozoic 3. Proterozoic 2. Archean 1. Hadean era large division of geologic time uniformitarianism Principle stating that geologic processes that occur today are similar to those that occurred in the past. period unit of geologic time smaller than an era epoch Division of geologic time smaller than a period Paleozoic Era Oldest era of the Phanerozoic Eon. Most life lived in the ocean with few reptiles on land Mesozoic Era Middle era of the Phanerozoic Eon. Age of the dinosaurs Cenozoic Era The youngest of the Phanerozoic Eon. The rise of mammals and the era we are presently in .