Classroom presentations to accompany Understanding Earth , 3rd edition

1. Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 21 Deformation of the Continental Crust

2. Deformation of the Continental Crust

3. Deformation of continental crust • Since continents are not destroyed by subduction, we look here for the ancient history of Earth. • orogeny: sum of the tectonic forces (i.e., deformation, magmatism, metamorphism, erosion)that produce mountain belts

4. Pangaea 250 Million Years Ago Fig.21.1

5. Mountains and Mountain Building Mountains are one part of the continuum of plate tectonics—the most evident one. Example: Limestones at the top of Mount Everest.

6. Structures of continents 1) Continents are made and deformed by plate motion. 2) Continents are older than oceanic crust. 3) Lithosphere floats on a viscous layer below (isostasy).

7. Alfred Wegener: Father of Continental DriftandGrandfather of Plate Tectonics Fig.21.1

8. Age of the Continental Crust Blue areas mark continental crust beneath the ocean Fig.21.2

9. Major Tectonic Features of North America Fig.21.3

10. Deformed and Metamorphosed Canadian Shield Fig.21.4

11. Continental characteristics • Granitic-andesitic composition • 30–70 km thick • 1/3 of Earth surface • Complex structures • Up to 4.0 Ga old

12. Three basic structural components of continents • Shields • Stable platforms • Folded mountain belts

13. Shields (e.g., Canada) • Low elevation and relatively flat • ”Basement complex" of metamorphic and igneous rocks • Composed of a series of zones that were once highly mobile and tectonically active

14. Stable platforms • Shields covered with a series of horizontal sedimentary rocks • Sandstones, limestones, and shales deposited in ancient shallow seas • Many transgressions, regresssions caused by changes in spreading rate

15. Mountain belts • Relatively narrow zones of folded, compressed rocks (and associated magmatism) • Formed at convergent plate boundaries • Two major active belts: Cordilleran (Rockies-Andes), Alps-Himalayan • Older examples: Appalachians, Urals

16. Mountain types Folded—Alps, Himalaya, Appalachians Fault block—Basin and Range Upwarped—Adirondacks Volcanic—Cascades

17. Stacked Sheets of Continental Crust Due to Convergence of Continental Plates Fig.21.5

18. Indian plate subducts beneath Eurasian plate 60 million years ago Fig.21.6a

19. Indian subcontinent collides with Tibet 40–60 million years ago Fig.21.6b

20. Accretionary wedge and forearc deposits thrust northward onto Tibet Approximately 40–20 million years ago Fig.21.6c

21. Main boundary fault develops 10–20 million years ago Fig.21.6d

23. Appalachian Mountains Fig.21.7

24. Physiographic Provinces of the Western United States A’ Line of cross section A Fig.21.8

26. Cross section of the Cordillera from San Francisco to Denver A A’ Fig.21.9

27. Volcanic Origin,e.g. Cascades Fig.21.10a

28. Upwarped with Reverse Faults,e.g. Central Rocky Mountians Fig.21.10b

29. Tilted Normal Fault Blocks,e.g. Basin and Range Province Fig.21.10c

30. Folded Rocks,e.g. the Appalachian Ridge and Valley Fig.21.10d

31. Overlapping Thrust Faults,e.g. the Himalayas Fig.21.1

32. Typical Basin and Range Topography Fig.21.11

33. Triassic Rift Valleys of Connecticut Fig.21.12

34. Inferred Thickness of Mesozoic and Cenozoic Sedimentary Rocks Fig.21.13

35. Idealized Cross Sectionof Basin and Dome Structures Fig.21.14

36. Black Hills of South Dakota:a Dome Structure Fig.21.15

37. Uplift Formed by Removal of Ice Sheet Fig.21.16a

38. Uplift Caused by HeatingSubsidence Caused by Cooling Fig.21.16b

39. Uplift Caused by HeatingSubsidence Caused by Extension Fig.21.16c

40. Uplift Caused by Rising Mantle Plume Fig.21.16d

41. Raised Beaches Due to Isostatic Uplift Fig.21.17

42. Effects of subsidence on Venice Raised sidewalk Fig.21.18

43. Present Rates of Uplift and Subsidence Fig.21.19