1. Earth’s Story 6.1 & 6.2

2. 1788 James Hutton Theory of the Earth Uniformitarianism

3. Present is the key to the past

4. Main concepts of uniformitarianism: Geologic processes we see now were active in the past. The physical, chemical & biological laws that operate today have operated throughout Earth’s history. (Earth Science, Tarbuck…) Earth’s physical features were formed by these same processes over long periods of time.

5. 1830s Charles Lyell Reintroduced uniformitarianism Now widely accepted by scientists

6. Catastrophes Occasionally occur Example: 65 mya asteroid hit Earth Dinosaur extinction

7. Homework Read pages 152 - 155

8. Paleontology Study of past life paleobotanists

9. 6.2 Relative Dating: Which Came First?

10. Law of Superposition Younger rocks lie above older rocks http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page03.cfm http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page03.cfm

11. Principle of Original Horizontality Sediments are deposited horizontally. So…if we see beds of sedimentary rock that are folded or tilted, they were deformed after deposition. http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page04.cfm http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page04.cfm

12. Law of Cross-cutting Relationships An igneous intrusion is younger than the layers which it cuts. http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page08.cfm http://www.classzone.com/books/earth_scien ce/terc/content/investigations/es2903/es2903 page08.cfm

13. Law of Cross-cutting relationships If a fault or intrusive rock cuts through other rocks, then it is younger. http://www.earthscienceworld.org/images/search/results.html?Keyword=Cross-Cutting

14. Law of lava flows A lava flow is younger than the layers which it covers.

15. What Can Cause Disturbances? Folding Faulting Intrusion Erosion

16. Inclusions When one rock has pieces of another included in it The rock containing the inclusions is younger.

17. What Do We See? Unconformity Break in geologic record Erosion Lack of deposition Can represent long or short time period

18. Unconformities Disconformity Nonconformity Angular Unconformity

19. Disconformity Part of sequence of parallel rock layers is missing

20. Disconformity at which about one million years of stratigraphic record is missing, near Gladeville in central Tennessee, U.S.A.,

21. Nonconformity Sedimentary rock layers lie on top of eroded surface of nonlayered igneous or metamorphic rock

22. Nonconformity space-shuttle views of the Sinai Peninsula

23. Angular Unconformity Horizontal layers found on tilted or folded rocks

24. Angular Unconformity northern Utah

25. Other photos of unconformities http://www.earthscienceworld.org/images/sea rch/results.html?Keyword=Cross%20Sections http://www.earthscienceworld.org/images/sea rch/results.html?Keyword=Cross%20Sections

26. Homework Read pages 156 - 161

27. Output Draw a geologic column block diagram. Show an: At least 3 sedimentary layers Angular unconformity Igneous inclusion List the relative ages from oldest to youngest.