Geology Vocabulary

3. rock formed when layers of sediments were pressed and cemented together
6. the oldest and longest span of geologic time
8. a crack in the earth's crust
10. rock formed from cooled magma or lava
12. The science of classifying organisms
14. a trait that helps an organism survive in a particular environment
15. body parts of different organisms that have a similar structure but not necessarily a similar function (supports theory of evolution from a common ancestor)
17. relating to the land
19. Smallest unit of geologic time
20. middle life (245-144 million years ago); rise of mammals and dinosaurs; the rise of birds; extinction of dinosaurs, rise of flowering plants

1. Index fossil. A group of hard-shelled animals whose body had three sections, lived in shallow seas, and became extinct about 245 million years ago.
2. Rocks changed by intense heat or extreme pressure
4. the theory that changes in the earth's crust during geological history have resulted chiefly from sudden violent and unusual events.
5. The geologic principle that the same geologic processes that operate today operated in the past to change Earth's surface
7. an era occurring between 570 million and 230 million years ago, characterized by the advent of fish, insects, and reptiles
9. no longer in existence
11. a gap in the rock layer that is due to erosion or periods without any deposition
13. gradual change over time
16. era that began about 66 million years ago, known as the "Age of Mammals"
18. body parts of different organisms that perform similar functions but do not have similar structures (does not support theory of a common ancestor)