Mountain Building and Geologic Structures

1. Mountain Building and Geologic Structures

2. Can you name these mountains? Caledonians Urals Appalachians Alps Rocky Mountains Himalayas • Andes Urals Appalachians Caledonians • Great Dividing Range Himalayas Alps Rockies Andes Great Dividing Range

3. Mountain Building (Orogenesis) Processes What Processes Build Mountains? • Volcanic Activity • Tectonic Activity • Folding – bending of rock • Faulting – breaking of rock

4. What Kind of Volcano?

5. What Type of Igneous Structure? • Granitic Batholith – Sierra Nevada

6. Mountain Building • Mountain building processes thicken the crust • Mountains can be twice as thick as the average continental crust (70 K versus 35 K) • Mountains have deep roots

7. Isostasy and Isostatic Adjustment • Erosion removes weight • Crust rises • Eventually uniform thickness

8. How Do Rocks React to Stress? • Compression • Crumpling • Tension • Stretching • Shear Stress • Grind past

9. Rock Deformation • Rocks deform under stress • Temporarily • elastic deformation • Permanently • Plastic deformation - folds • Brittle deformation - faults

10. Folding Compression causes: Fold mountains and thrust faults Crustal shortening Thicker Crust in mountains

11. Folding

12. Folding – Anticlines and Synclines

13. Appalachian Ridge and Valleys Are Fold Mountains

14. Topography Does Not Always Reflect Structure A B C • Some anticlines form valleys • Some synclines form ridges Rock hardness determines the topography • Hard rock forms ridges, soft rock forms valleys

15. Erosion of Deformed Sedimentary Rock

16. Most Major Mountain Belts Include Fold Mountains • Compression crumples sediments when plates converge • Alpine structure includes complex folds and thrust faults European Alps

17. What is a Fault? • Faults are fractures in the earth’s crust along which movement has taken place • Joints are fractures that have not moved • Faults can be a few feet or hundreds of miles long

18. What stress produced these faults? Compression Tension Compression Shear stress

19. Normal and Reverse Faults • What is normal about a normal fault? • What is reversed about a reverse fault? • In a NORMAL fault, the upper block (hanging wall) drops under the influence of gravity

20. What Kind of Fault? • A Reverse fault

21. What Kind of a Fault? • Normal Fault

22. What Kind of a Fault? • Strike-slip fault

23. Can Tension and Normal Faults Produce Mountains? • Fault-Block Mountains • Great Basin or Basin and Range

24. Great Basin • After subduction of Farallon Plate • North America moved over a rift zone

25. Basin and Range • Crustal stretching cause some tilted blocks to slump and forms basins • A block surrounded by parallel faults may drop to form a graben • The remaining blocks form horst block mountains

26. What is the relationship between mountains and plate tectonics? Some mountains are volcanic (igneous) mountains • Convergent Plate Boundaries • Cascade Volcanic Mountains • Sierra Nevada Granitic Batholith • Divergent Plate Boundaries • Kilimanjaro in East Africa • Mount Hekla in Iceland • Hot Spots • Mauna Loa in Hawaii

27. What is the relationship between mountains and plate tectonics? • Many mountains coincide with currently active convergent plate boundaries • Andes • Himalayas • Alps • Most of these mountains are complex involving folding, faulting, and volcanism

28. What is the relationship between mountains and plate tectonics? • Some mountains coincide with OLD plate boundaries • Ural Mountains in Russia • Appalachians in Eastern United States

29. Evolution of the Appalachians • 600 million years ago • Passive margin • 500 million years ago • Ocean-Continent Convergent Boundary • Subduction zone volcanism • 350-400 million years • Newfoundland-Caledonian collision • Africa approaches

30. Evolution of the Appalachians • 250 million years ago • Continent-Continent America-Africa • Appalachians fold and fault • 200 million years ago • Divergent rift zone • Today • Part of Africa left behind • Passive margin

31. California Topography

32. Identify These Geomorphic Regions Modoc Plateau Klamath Mountains Cascade Ranges

33. What Kind of Mountain? Composite Cone – Mount Shasta

34. What Region?

35. How Did the Coast Range Form? Slices of sea floor, folded sediments, island arcs, and terranes from other places accreted to the Coast Range Complex Mountains

36. Terrane Map Aleutian Trench, Alaska why Alaska gets such big Earthquakes Ultimate destination of LA

37. Terrane Formation

38. Alaska State made entirely of accreted terranes sutures, faulting between them steep topography Denali 20,320 Mt. McKinley

39. Bay Area Terranes Franciscan Group Marin Headlands Nicasio Reservoir Alcatraz Permanente Yolla Bolly Novato Quarry Yerba Buena Richmond Salinian Red Rock? Angel Island? each of these bounded by faults much more than just San Andreas and Hayward

40. What Kind of Fault? Transform Fault Strike-slip Horizontal movement

41. What Region? Flood Basalts What structure?

42. Identify This Geomorphic Region Central Valley A sediment-filled basin

43. What Region? Transverse Ranges – Complex Mountains

44. What Region?

45. Identify The Structure in this Geomorphic Region Peninsular Ranges A Granitic Batholith

46. What Region? Salton Trough A Graben

47. What Region? What Structure?

48. What Region? Klamath Mountains Complex Mountains

49. Klamath Terranes this map shows 10 distinct terranes and many sub-terranes how do you divide them? subjective depends on purpose how small is too small to call a terrane?

50. A – Klamath Mountains • Complex Mountains • B – Coast Ranges • Complex Mountains • C – Cascade Ranges • Composite Volcanoes • D – Modoc Plateau • Flood Basalts • E – Sierra Nevada • Granitic Batholith • F – Central Valley • Sediment filled basin • G – H Great Basin • Fault Block Mountains • I - Transverse Range • Complex Mountains • J – Peninsula Ranges • Granitic batholiths • K – Salton Trough • Graben