1. Interpreting Earth’s Rocks to Determine Its Past History

3. Geologic Time Relative dating - sequence of geologic events in a region (order of past events) Absolute dating – numeric- time in years; use radioactive isotopes. How do we know how old something is?

4. James Hutton: The father of modern geology (1726-1797) Uniformitarianism: processes acting on earth today have done so in the same way as in the past “The present is the key to the past.”

5. Examples of uniformitarianism Petoskey stones Striations Rock formation Paleoclimates Earthquake location Grand Canyon What else?

6. Determining Geologic History: Geologists are like CSI detectives wanting to know Where?, When?, Why?, How? Sometimes very little “evidence” remains (exposure, erosion) Evidence has been moved or tampered with! Rocks have been moved (faults, folds) Usually no witnesses!

7. http://www.angelfire.com/az3/mohgameil/Layering4.jpg Principle of Superposition Oldest layer on bottom (if tectonically undisturbed) Younger Older

8. Principle of Superposition In horizontal rock layers, the oldest and first formed is on the bottom. 5 is the youngest because it is on the top, closest to the surface.

9. http://www.calstatela.edu/faculty/acolvil/sediment/superposition.jpg The Grand Canyon

11. Principle of Original Horizontality Folding happened AFTER rocks were deposited

12. folded rock layers = compression by tectonic activity

13. Cross-Cutting Relationships An igneous intrusion (or fault) is younger than the rock layers that it cuts across. fault oldest These are younger than the surrounding rock youngest

14. Write the order of events that have taken place above. List (oldest - 1 to youngest - 6)

15. Cross-Cutting Relationships Order the events

16. ? A C B D E Order the rock layers above from oldest to youngest. Is this an example of absolute or relative dating?

17. Which came first? The first layer deposited and the oldest is D, followed by C, A, B, and E. D D D C C A B B E

18. practice

19. Index fossils Fossils that lived for a short time can be used to date layers Found world wide Examples?

20. Order the layers 1-7

22. Unconformities = “Missing Time” Result of erosion

23. Angular Unconformities Folded layers on bottom, flat layers on top angular unconformity ( rock layers have been eroded away) rock layers are eroded new horizontal layers are deposited

24. FEDCBA Angular Unconformity

25. The Great Unconformity – Grand Canyon, AZ

26. Granite sedimentary rock layers Cambrian Precambrian Nonconformity – igneous rocks on bottom; overlain by sedimentary rocks

27. Nonconformity

28. Disconformity DISCONFORMITY:Missing rock layers (sedimentary) Very hard to see

29. Disconformities

30. Let’s Play…. Name the UNCONFORMITY!

31. Siccar Point, Scotland

33. http://www001.upp.so-net.ne.jp/fl-fg/06-02.htm

36. http://www.env.duke.edu/eos/geo41/st013.gif granite sandstone shale limestone

37. http://www001.upp.so-net.ne.jp/fl-fg/06-02.htm

39. http://www.env.duke.edu/eos/geo41/st013.gif granite sandstone shale limestone

40. Resources http://courses.geo.ucalgary.ca/glgy209L03/docs/Lecture15_GLGY209_six.pdf http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images2/law_of_superposition_b.jpg http://www.science.sjsu.edu/scied/255/ppt/superposition/img025.jpg http://www.gpc.peachnet.edu/~jsummero/Cross-cutting-a.jpg http://www.gc.maricopa.edu/appliedscience/gjc-nsf/images/CRH0204.JPG http://maverick.gc.maricopa.edu/appliedscience/gjcweb/geomap/images/ang.unconf.jpg http://www.geog.ouc.bc.ca/physgeog/contents/images/hutton.jpg http://www.bigbendpaleo.com/Photo%20Gallery/Big%20Bend%20Region,%20Texas/Big% 20Bend%20National%20Park%20-%20Syncline%20-%20Javalina%20Creek%20- %2020%20June%201995.jpghttp://www.bigbendpaleo.com/Photo%20Gallery/Big%20Bend%20Region,%20Texas/Big% 20Bend%20National%20Park%20-%20Syncline%20-%20Javalina%20Creek%20- %2020%20June%201995.jpg http://geoimages.berkeley.edu/GeoImages/Johnson/Images/Large/CD3/028.jpg http://www.vvdailypress.com/travel/rainbow/images/rock.jpg http://academic.emporia.edu/aberjame/struc_geo/folds/fold06.jpg http://www.geology.pitt.edu/images/folds.jpg http://faculty.evansville.edu/de3/b39902/PPoint/Geologic%20Time/img007.jpg http://www.photo.net/photo/pcd2882/grand-canyon-region-aerial-85.3.jpg http://www.cowanstark.com/horsehoe-bend.jpg http://home.flash.net/~alanm52/Cross_cutting.jpg http://www- class.unl.edu/geol101i/images/igneous%20images/Black%20Canyon%20Gunnison.jpghttp://www- class.unl.edu/geol101i/images/igneous%20images/Black%20Canyon%20Gunnison.jpg http://freespace.virgin.net/craven.pendle/stratigraphy/unconformity.jpg

41. http://comp.uark.edu/~sboss/siccar.jpg http://www.pittstate.edu/services/scied/Teachers/Field/Camp/Us67-1/us67cut.jpg http://maverick.gc.maricopa.edu/appliedscience/gjcweb/geomap/images/MW8-11.jpg http://www3.uakron.edu/geology/Foos/parks/rmgcan2.html http://www.ldeo.columbia.edu/edu/dees/ees/ies2/slides/disconformity.gif http://geology.lssu.edu/NS102/images/figure%2009-06.gif http://www.crienterprises.com/C-Assets/J-Hanifa-Unconf-W-Birk.jpg http://www.uoguelph.ca/~sadura/stgref/stg32b.gif http://www.geo-outdoors.info/images/eye_protection.jpg http://enterprise.cc.uakron.edu/geology/natscigeo/Lectures/time/gtime1.htm