1. Mountain Building Chapter 11

2. WHERE MOUNTAINS FORM 11.1

3. What is a Mountain? Large mass of rock Rises far above its base

4. A. Mountain Belts Most form in long belts that follow convergent plate boundaries Some are old boundaries, some are current boundaries Appalachians – OLD boundary Himalayas – Current boundary

6. Appalachians Himalayas

7. B. Continental Margins Boundary between continental and ocean crusts Active Margins –Along plate boundaries Passive Margins –Not at plate boundaries

8. Atlantic Continental Margin Passive Creates Mountain Building Materials

9. Active Continental Margin Mountain Building Happens Subducting Boundaries Usually Volcanically Active Earthquake Prone

11. How are these margins related? Passive margins contain a lot of sediment When that passive margin becomes active, those sediments will become part of the new mountains

12. HOW MOUNTAINS FORM 11.2

13. STRESS!!!! Stress within the earth causes rock to break or fold

14. A. Types of Stress 1. Compression –Rock layers are being squeezed inward –Makes layers thicker and shorter

15. . 2. Tension –Layers are stretched –Makes rocks thinner and longer

16. 3. Shear Stress –Rocks are being pushed in opposite directions –Distorts the rock along the plane

17. Where does this happen? Along plate boundaries Usually all occur together Different rocks respond differently to the three types of stress

18. B. Folds Along continental margins Stress causes rocks to warp and crumple Over time, erosion exposes the rock

19. Anticlines An upfold in the rock strata

20. Synclines A downfold in rock strata

21. Limbs The sides of an anticline or syncline

22. C. Faults Fault plane – the plane along which movement in earth’s crust occurs

23. Above the Fault Plane: Foot Wall Below the Fault Plane: Hanging Wall

24. 1. Normal Fault Hanging wall moves DOWN Tension is pulling crust apart

25. 2. Reverse Fault Hanging wall moves UP Compression pushing crust together

26. 3. Thrust Fault A type of reverse fault The major difference: the angle of the fault plane –45 degrees or less from horizontal

27. 4. Strike-Slip Fault Rocks on opposite sides of the fault move past each other

28. 5. Joints A break in the bedrock – no movement has occurred Usually in the form of a plane Gives a channel in which fluids (molten material, soil, water) can move

29. TYPES OF MOUNTAINS 11.3

30. A. Folded Mountains Two colliding continental plates Rocks don’t break, they crumple Ocean between plates must disappear first –Due to subduction –Continues until crusts meet

31. Himalayas are Folded

32. B. Dome mountains A type of folded mountain Nearly circular Usually solitary

33. Plutonic Dome Made by plutonic intrusion Pushes up older rock Core of mountain is younger

34. Tectonic Dome Made by uplifted rock layers Rocks at core are older –No new material –Layers erode, exposing older rock

35. C. Volcanic Mountains Different types of volcanoes form in different areas (remember chapter 9)

36. D. Fault-Block Mountains Formed by Compression or Tension Blocks of crust are dropped (tension) or lifted (compression) Form Normal or Reverse faults

37. Grabens and Horst Horst- formed by compressional forces Graben – formed by tension forces