Unit 3: Geologic Time Vocabulary

5. scientists that study prehistoric life that includes study of fossils and organisms' evolution.
7. fossils: a fossil of a footprint, burrow, or other trace of an animal rather than of the animal itself.
9. hardened rein of ancient trees in which some insects have been preserved.
10. Age: the true age of a rock or fossil.
12. process by which organic matter exposed to minerals over a long period is turned into a story substance.
13. drying of a part of the body into a hard mass; process of preserving a dead body.
18. of superposition: In a undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below.
20. a piece of fossilized dung.

1. that the erosional surface separates older metamorphic/intrusive rocks from younger sedimentary rocks.
2. process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.
3. two sedimentary rock layers that are separated by erosional surface.
4. stomach stone or gizzard stones; a small stone swallowed by a bird, reptile, or fish to aid digestion in the gizzard.
6. an annual deposit usually consisting of two rock layers.
8. the amount of time necessary for one half of the nuclei in a sample to decay to its stable isotopes.
11. plane: the surface that separates one layer or bed of stratified rock from another.
14. breaks in the rock record.
15. fossils: fossils that are used to define and identify geologic periods.
16. unconformity: appears as tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata.
17. of uniformitarianism: principle that the answers to the past can be found in the present, meaning that everything is uniform in how it works.
19. age: comparison of age based on which object (or event) is older or younger than some other object or event.