CHAPTER 5: Fossils and Geologic Time

1. CHAPTER 5: Fossils and Geologic Time TOPIC 1: The Geologic Column

2. Introduction • As rocks are weathered, eroded, and deposited their sediments form layers that eventually become compacted and cemented into solid rock called sedimentary rock. These rocks play an important role in helping geologists and paleontologists (scientists who study ancient life forms) to reconstruct the history of Earth and life on it.

3. Item #1 • The location of rock layers and the fossils they contain relative to one another allows scientists to determine whether an object or event is older or younger than another object or event. This process is called ___________________ ____ and uses the principle of _________________________, which states that in an undisturbed sequence of sedimentary layers, __________________ rocks lie above _______________ rocks. Relative dating superposition younger older

6. Grand Canyon model

7. Item #2 To reconstruct the complete history of Earth, layers of rock from around the world must be compiled into one single sequence (from oldest on the bottom to youngest on the top) called the _________________ ______________________. This is like collecting pages from a book that have been torn out and putting them together in the correct order to reconstruct the story. Geologic column

10. Item #3 There is no one location on Earth that has rock layers formed during all periods of earth’s history. These breaks in the geologic record in a sequence of rock layers is called a(n) ________________________________. unconformity

11. Unconformities

12. 225 myo 525 myo (200 my gap) 742 myo 2 byo 1.5 byo

13. Item #4 Breaks in the rock record (missing layers) can result from _______________________, meaning that the supply of sediment is cut-off. This usually occurs when uplift raises the land above sea level for a period of time (since sedimentary rocks form offshore, underwater). They also can be formed and later removed when the land is raised by the process of __________________. nondeposition erosion

14. rock puzzles