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

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

3. James Hutton: The father of modern geology (1726-1797) Uniformitarianism: “The present is the key to the past.”

4. Examples of uniformitarianism Petoskey stones and past climates How sandstone forms Grand Canyon formation Dino reconstruction

5. 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!

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

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

8. Principle of Original Horizontality Sediments are originally deposited as horizontal (or near horizontal) beds- use with folded layers.

9. folded rock layers = compression by tectonic activity

10. 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

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

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

13. 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

14. List the order of events that took place: earthquake deposit D deposit B deposit G intrusive lava rocky deposit R river cuts through deposit E deposit A

15. Unconformities = “Missing Time”

16. Angular Unconformities Folded layers below horizontal layers. angular unconformity ( rock layers have been eroded away) rock layers are eroded new horizontal layers are deposited

17. FEDCBA Angular Unconformity sedimentary rocks above and below unconformity surface with rocks below tilted at an angle

18. The Great Unconformity – Grand Canyon, AZ

19. Granite sedimentary rock layers Cambrian Precambrian Nonconformity – younger sedimentary rocks rest on older igneous rocks

20. Nonconformity

21. Disconformity DISCONFORMITY:Missing rock layers (sedimentary) Very hard to pick out

22. Disconformities

23. Siccar Point, Scotland

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

25. http://spot.pcc.edu/~mhutson/160/shore_acres.jpg

27. 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

28. 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