1. Deformation of the Crust
5.1 How the crust is deformed
5.2 The results of stress
5.3 Mountain formation

2. Faulting
This tends to occur under cooler conditions and lower pressure near the Earth’s surface
When a break occurs in rock with no movement it is called a fracture
When a break occurs and the rocks do move it is called a fault

3. Faults
The fault plane is the surface of the fault along which any motion occurs
The part of the fault above the fault plane is the hanging wall and the part of the fault below the fault plane is the footwall
There are 4 types of faults: normal, reverse, thrust and strike-slip

4. Small normal faults, Malta

5. Normal fault
The hanging wall moves downwards with respect to the footwall
This happens where the Earth is under tension, for example along divergent boundaries
Great Rift Valley (Africa)
Normal faults in volcanic ashes and paleo-soils, El Salvador.

8. Bishop Tuff lake sediments, Owen Valley, CA.
                                                    
Bishop Tuff lake sediments, Owen Valley, CA.
This mountain of nicely layered limestones shows several sets of normal faults offsetting the prominent white band near the top of the mountain. If you focus on each fault, the offset of each hanging wall from each foot wall indicates normal fault motion.

9. Round O Quarry, Lancashire, England

10. Reverse fault
Occurs when the hanging wall moves up with respect to the footwall
Caused by compression
For example when two plates collide the compression causes the fault to thicken and rocks to shorten

14. Fault planes are nearly vertical but so tilt to the left in a steep series of reverse faults.

15. Small reverse thrust on a road cut in Japan

16. Thrust fault
A reverse fault where the fault plane sips below 45o or less from the horizontal
Common in the Rockies and Alps
Sometimes called a blind fault meaning there is no deformation at the surface (no visible break)
Difficult to detect or locate
Sometimes the only clue is what appears to be a fold at the surface that is actually the thrust fault pushing overlying layers upwards

17. Thrust fault in the Andes, Chile.

19. Onondaga limestone, New York state.

21. Monos de Agua Canyon, Chile

22. Major thrust fault – White Rock, Wyoming

23. Strike-slip fault
This occurs when rocks on opposite dies of the fault plane move horizontally past each other
Often occurs are transform boundaries
San Andreas Fault
very long strike-skip faults are found in the Himalayas (thousands of km long)

26. This fault can be recognized from the air as a line with dissimilar surface features on either side because the crustal blocks have shifted horizontally relative to each other; the movement is mainly horizontal making this a strike-slip fault.

27. Joints
These are breaks in the bedrock but unlike faults joints are breaks that appear where no apparent movement has occurred
They are the results of the same stresses the lift, tilt and fold rock layers into mountains
One of the most common rock structures, appear on the surface of a rock outcrop as a line or groups of lines
They provide channels for the flow of fluids such as water and magma (can form vein deposits)

28.                       
Looking down (note shoe)

29. Joints in a rock unit exposed in a cliff

30. Columnar joints in basalt caused by systematic fracturing during cooling of basaltic lava, Turkey.

31. Joints in a sandstone unit widened by water erosion, Henry Mountains, Utah.

32. Mountain building
Mountains form along continental margins where crusts meet
Andes and Rockies – oceanic and continental
Himalayas – two continental crusts
Island arcs (eg. Mariana Islands) – two oceanic plates

33. Mountain building
Stress is applied to rocks at convergent plate boundaries
Compression, tension and shearing all contribute to the process
Fracturing (faulting) near the cooler surface and folding in warmer deeper layers
Also the type of material the rock is formed from will influence how it reacts

34. Fold and thrust

35. Continental margins
This is a boundary between continental crusts and oceanic crust
Active margins occur along plate boundaries (subduction zones)
For example there are active continental crusts along the west coasts of North and South America
This is one of the reason for the many earthquakes and volcanoes that affect South America

37. The convergence of the Nazca and South American Plates has deformed and pushed up limestone strata to form the towering peaks of the Andes, as seen here in the Pachapaqui mining area in Peru.

38. Continental margins
Passive continental margins are stable areas because they do not occur at plate margins
For example, along the east coast of North America eroded sediments from the Appalachians have formed a wedge 250 km long and 10 km deep
In the future the material forming passive margins my become involved in mountain building as plates move and collide in the future

39. Continental margin of the northeastern United States

40. Mountains
Mountain range – a group of adjacent mountains with the same general shape and structure
Cascades, Sierras
Mountain system
Group of adjacent mountain ranges
Rockies, Andes

41. Mountain Ranges
Grampian Mountains, Australia

43. Mountains Mountain belt Most of the world’s mountains occur in belts
E.g. North American Cordillera runs from Alaska to Mexico
They are regions where mountains are being formed or have been formed in the past
For example, the Appalachians formed part of a previous plate boundary millions of years ago

44. Folded Mountains
When two continental crusts collide rock can fold and crumple into folded mountains
Form some of the highest mountains in the world such as the Himalayas, Rockies, Urals, Alps, Appalachians etc.

45. Folded Mountains
For this to happen the ocean basin between the continents must close
This brings the two continental crusts into direct contact
No more subduction because the crusts now have equal densities

46. The Himalayan mountain range dramatically demonstrates one of the most visible and spectacular consequences of plate tectonics.
When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways.

47. Folded Mountains
Form plateaus – uplifted areas form where thick horizontal layers are pushed up gently enough that they don’t break and remain flat rather than bending
Tibetan Plateau next to the Himalayas
Plateaus can also form from igneous rock extrusions

48. The collision between the Indian and Eurasian plates has pushed up the Himalayas and the Tibetan Plateau. The cross sections show the evolution of the Himalayas and the displacement of slivers of continental crust during this collision. The reference points (small squares) show the amount of uplift of an imaginary point in the Earth's crust during this mountain-building process.

49. Tibetan plateau

50. Dome Mountains A nearly circular folded mountain
Individual insolated structures, not part of mountain belts, usually in areas of flat lying sedimentary rock
Formed by igneous intrusions (plutonic dome mountains) such as laccoliths
Some on the border of the Colorado plateau and the Rockies

52. Dome Mountains
Tectonic dome mountains are formed by uplifting forces that arch the rock layers upwards
Adirondack Mountains, Black Hills

53. Located in New York, near Ontario/Quebec border

54. Tectonic Dome Mountains
Black Hills, South Dakota

55. Black Hills

56. Fault-Block Mountains
These mountain form from the forces of tension instead of compression
For example in some parts of western North America the crust is slowly being uplifted
This causes the crust to stretch and crack forming normal faults along the surface
Examples include the Sierra Nevadas and Tetons (Wyoming)

58. Road cut near Denver Colorado

59. Hart Mountain (a massive block fault ridge) at the north end of Lake Crump, Oregon.

60. The Teton Range is one of Earth’s most impressive examples of fault-block mountains, along which movement is estimated to average about one foot per 300–400 years. Although the Tetons are the youngest mountains of the Rocky Mountain chain, they contain some of its oldest rocks, dating back about 2.8 million years.

62. Horsts
Forms when a block is forced upwards due to tension between two normal faults

63. Grabben
Forms when tension forces rocks apart and between normal faults on either side of the valley large blocks of crust have dropped
Great Rift Valley, Death Valley
Looking down on Death Valley from Zabriskie Point