|
 Oxygen | gas produced by anaerobic prokaryotes during Precambrian Time. |
| paleontologist | a scientist who studies fossils and ancient life. |
| rock cycle | the process involving the formation and recycling of rock. |
| metamorphic rock | rock formed when existing rock is squeezed and/or partly melted. |
| catastrophism | the idea that geologic events occur suddenly |
| Cenozoic era | era dominated by mammals |
| anaerobic | living without oxygen |
| Precambrian time | period when there was no oxygen in Earth's atmosphere |
| Paleozoic era | era when plants and animals first lived on land. |
| ozone | forms a layer in the atmosphere that shields solar radiation |
| extinct | when all of the members of a species die |
| sedimentary rock | rock formed when sediment is lithified |
| uniformitarianism | the idea that geologic processes that occur today also occurred in the past. |
| mass extinction | when a large number of species die off in a short period of time |
| geologic time scale | organizes the history of life on Earth |
| plate tectonics | the study of the movements of Earth's continental plates |
| igneous rock | rock formed when lava and magma cools |
| Pangaea | a large landmass that contained all the present-day continents |
| superposition | principle that states younger rocks are on top of older rocks |
| fossil | the solidified remains or imprints of a once-living organism |
| absolute dating | dating method (using radioactive atoms) that determines a fossil or event's "exact" age |
| relative dating | dating method that compares the age of one specimen or event to another. |
| erosion | when sediment is carried away, usually by wind or water |
| weathering | the gradual breakdown of rock, usually by wind or water |