STRUCTURAL_GEOLOGY.ppt
- 1. The Soul Would Have No Rainbow, If The Eyes Had No Tears. Minquass
- 2. Structural Geology Danny M. Vaughn, Ph.D., CMS The study of how & why rocks fold, bend, & break.
- 3. Stress and Strain • Stress – an applied force. • Pressure – amount of force applied. • Lithostatic • Directed • Strain – a rock’s response to stress (deformation) • Shape • Volume
- 4. Types of Strain • Elastic deformation • Brittle failure • Plastic deformation Temporary deformation (until the elastic limit is surpassed) Slow, continuous, low stress conditions.
- 5. • Permanent deformation that occurs when a rock breaks. • Occurs w/ low temperature, low, but sudden pressure changes. • Mineral bonds break along a zone of maximum stress. Types of Strain • Elastic deformation • Brittle failure • Plastic deformation
- 6. Types of Strain • Elastic deformation • Brittle failure • Plastic deformation • Permanent deformation that occurs when a rock changes its shape without breaking. • High temperature, high pressure conditions. • Atoms move from maximum to lower stress areas.
- 7. Factors Affecting Rock Deformation • Magnitude of stress • Rate stress applied • Temperature • Pressure • Composition How much pressure & at what rate of speed the force is applied. What is magnitude? What does rate of stress mean?
- 8. Factors Affecting Rock Deformation • Magnitude of stress • Rate stress applied • Temperature • Pressure • Composition Higher temperatures & pressure result in plastic deformation.
- 9. Factors Affecting Rock Deformation • Magnitude of stress • Rate stress applied • Temperature • Pressure • Composition • Time • Water weakens bonds creating plastic behavior. • Mineralogy (bonds) can override temperature, pressure, & the rate of stress. • Pyroxene & garnet (strong). • Calcite & mica (weak). • Continuous low measures of stress over time result in plastic behavior.
- 10. Types of Stress • Compression • Tension • Shear • Torque
- 12. Bearing & Azimuth Bearing – a quadrant system of angular measure. Azimuth – a continuous measure of angular measure.
- 13. Studying Deformed Rocks Measuring Strike and Dip Strike - The compass direction of the line that forms at the intersection of the plane and an imaginary horizontal plane Dip - The angle at which a plane is inclined relative to the horizontal
- 15. Strike and Dip
- 16. Strike and Dip Rule of Structure “V” ┤
- 17. Plastic Deformation - Folds
- 18. Photomicrograph of Folded Minerals
- 19. Types of Folds • Anticlines • Synclines • Domes • Basins
- 20. Fold Symmetry
- 21. Fold Symmetry
- 22. Types of Folds • Anticlines • Synclines • Domes • Basins Asymmetric Folds
- 23. Recumbent Fold
- 24. Folding Compressional forces (convergent plate boundaries)
- 25. Types of Folds Landforms Following Erosion
- 26. When the angle of plunge of the fold is inclined along the axial plane, the fold is said to be plunging.
- 28. Valley & Ridge Physiographic Province Central Pennsylvania
- 29. The nose of the anticline is expressed as a long, tapering dip slope, while the nose of the syncline is typically blunt. Anticlines tend to be more cigar-shaped in body. The steeper escarpment faces to the outside of the structure in a syncline. The steeper escarpment faces the inside of the structure in an anticline. The oldest beds will be within the core (inside) of an anticline. The youngest beds will be within the core of a syncline. Summary Statements
- 30. Valley & Ridge Physiographic Province Central Pennsylvania
- 31. Types of Folds • Anticlines • Synclines • Domes • Basins
- 32. Types of Folds • Anticlines • Synclines • Domes • Basins
- 33. Black Hills Dome
- 34. Brittle Deformation - Joints Rock fractures with no evidence of movement
- 35. Brittle Deformation - Faults Rock fractures with evidence of movement Evidence of movement: • Displacement • Crushed rock along fault plane • Slickensides Faulting – fracturing w/ displacement due to one or more forms of stress.
- 36. Types of Faults Strike-slip faults Movement (slip) in the direction of strike (horizontal) Dip-slip faults Movement (slip) in the direction of dip (vertical)
- 37. Types of Faults Dip-slip faults
- 38. Normal Fault
- 39. Types of Faults Dip-slip faults • Normal fault • Reverse fault Hanging Wall Foot Wall
- 40. Types of Faults Horst & Graben
- 41. Types of Faults Horst & Graben
- 45. Block Faulted Mountains •Sierra-Nevada & Tetons. •Normal fault along base. • Tilted along a normal fault plane. •Intrusion of granitic magma.
- 46. Reverse Fault
- 47. Types of Faults Dip-slip faults • Normal fault • Reverse fault Hanging Wall Foot Wall
- 49. Chief Mountain
- 51. Types of Faults Strike-slip faults • Right-lateral • Left-lateral
- 52. Types of Faults Fault Planes
- 53. Plate Tectonics & Faulting
- 54. Plate Tectonics & Folding
- 55. Oceanic-Continental Collision • Formed Rockies, Andes, Cascades, Sierra of Central America, Plate Boundary Collisions
- 56. Continental-Continental Collision • Results in folding, overthrusting, faulting, & uplifting w/ overturned folds (Nappes). • Himalaya & Alps.
- 57. Oceanic-Oceanic Collision • Results in volcanic island arcs – Indonesia, Japan, Philippines, Aleutians.
- 58. Orogenesis - Mountain Building • Large scale crustal deformation. • Compressional forces, volcanism, capture of migrating terranes, intrusion of magma. • Rocky Mountains (Laramide Orogeny, 40 million yr. ago). • Sierra Nevadas (Sierra-Nevadan Orogeny, 35 million yrs. ago), batholithic intrusions 130-160 million yrs. ago. • Appalachians (Alleghany Orogeny, 250-300 millions yrs. ago w/ earlier episodes). • Alps (Alpine Orogeny, 20-120 million yrs. ago w/ many earlier episodes).
- 59. Folds, Faults, & Fossil Fuels
- 60. What can you say about the general structure of the rocks in this photograph?
- 61. How did Mexican Hat form? Why does it still exist?
- 62. How do you explain the existence these isolated monuments?
- 63. Why are these rocks shaped and aligned as they appear in this photograph?
- 64. Syncline, ramp anticline, & thrust fault. Where are they?
- 65. What class of rocks are the light pink? Why are they not aligned?
- 66. What does this surface represent? Striations, slickenside surface : A fault plane
- 67. What is structurally apparent about these rocks? Strike/slip faults
- 68. What is structurally apparent about these rocks? Reverse fault