1. Chapter 12 Clues to Earth’s Past

2. 12.1 Fossils 1. What can fossils tell us? - Where, when, and how organisms lived 2. 2. 2 most important conditions necessary for an organism to become a fossil: 1. To be buried quickly 2. Have hard parts

3. 3. 3. How an organism’s remains petrified: - Some or all of the original materials in the remains have been replaced by minerals. 4. 4. How an organism’s remains can become carbonaceous film: - The organism is buried by sediments which pile up increasing the heat and pressure. Gases and liquids are forced from body, thin film of carbon residue is left forming an outline.

4. Petrified Log

5. Trilobite

6. 5. 5. Process of fossilization as an organism is buried, becomes a mold, then a cast: A. The fossil begins to weather and erode as water moves through pores in rock layers. B. The fossil is eroded away, the harder rock surrounding it forms a mold. C. Sediments are carried into the mold and deposited. D. A cast is formed.

11. 6. Three ways that the original remains are preserved: 1. Frozen in ground 2. Trapped in amber 3. Trapped in tar

19. crustacean burrows -middle Jurassic

20. coprolite (dino poo)

21. 7. 7. Four types of information that trace fossils can tell about animals: 1. Size, weight, age 2. Speed animal was traveling 3. Lifestyle of animal 4. Social life of animal

22. 8. 8. What do scientists use index fossils for? - To date rock layers

23. 12.3 Relative Age of Rocks 1. 1. What does the principle of superposition state? - In a sequence of sedimentary rock layers, the oldest layer is on the bottom, the youngest on the top. 2. 2. How are sediments deposited? - In horizontal layers 3. 3. What is relative dating ? - Determining the order of events or relative ages of rocks by their position in sequence.

25. 4. What is unconformity? - A gap in the sequence. * Develops when sedimentary rock layers are uplifted, tilted and/or eroded away.

26. Angular Unconformity  Horizontal layers are uplifted, tilted, and eroded, then more layers are deposited horizontally.

31. Disconformity  Layers are deposited, uplifted, and eroded, more layers are deposited horizontally.

34. Nonconformity  Sedimentary layers are deposited on top of igneous or metamorphic rocks.