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Structural Geology

Structural Geology. Faulting. Structural Geology. Folding. Terminology. Stress – The force acting on a surface, force per unit area Deformation – change in shape or volume of rock in response to stress Strain – deformation resulting from stress. Stress. Uniform – compressional

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Structural Geology

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  1. Structural Geology Faulting

  2. Structural Geology Folding

  3. Terminology • Stress – The force acting on a surface, force per unit area • Deformation – change in shape or volume of rock in response to stress • Strain – deformation resulting from stress.

  4. Stress Uniform – compressional Differential – compressional tensional shear

  5. Types of Stress • Uniform stress – equal force applied in each direction

  6. Types of Stress • Differential stress – force applied is greater in one direction

  7. Types of Differential Stress

  8. Stress vs. Strain Earthquakes Folding Faulting Force Deformation

  9. Deformation 1. Elastic – nonpermanent, rock returns to original shape 2. Ductile (plastic) – permanent, rock flows or bends 3. Brittle – permanent, rock breaks

  10. Ductile Brittle

  11. Types of Deformation • 1. Elastic deformation – material returns to its original shape after stress is removed. • Example: rubber band Elastic limit – point beyond which permanent deformation occurs.

  12. Types of Deformation • 2. Ductile (plastic) deformation – permanent change in shape by bending or flowing. • Example: copper wire

  13. Types of Deformation • 3. Brittle deformation – permanent change in shape when the material fractures or cracks • Example: breaking a piece of slate

  14. Factors affecting Deformation • Temperature – as temperature increases, materials become more ductile. • Example: plastic 2. Confining Pressure – as pressure increases (weight of overlying rocks), materials become more ductile.

  15. Factors affecting Deformation • 3. Rate of deformation – if stress is applied rapidly, rocks will tend to be brittle. • Example: chewing gum 4. Composition of rocks – at the same temperature and pressure, some rocks will be more brittle than others. Example: slate (brittle) and copper (ductile)

  16. Measuring Deformation in the RocksStrike & Dip

  17. Geologic Map

  18. Geologic Map Geologic Profile Geologic Cross Section

  19. Types of Faults Classified by relative motion • Dip - Slip • Strike - Slip

  20. Dip – Slip Faults 1. Normal Fault 2. Reverse Fault high angle low angle – (Thrust Fault)

  21. Footwall and Hanging wall

  22. Normal Faulting

  23. Reverse Faulting

  24. Faults

  25. Strike-slip Faulting Left – lateral Right - lateral

  26. Faults

  27. http://earthquake.usgs.gov/regional/nca/virtualtour/bayarea.phphttp://earthquake.usgs.gov/regional/nca/virtualtour/bayarea.php

  28. Oblique - Slip Dip - Slip and Strike - Slip movement

  29. Summit Road Area, Santa Cruz Mountains

  30. MOSS LANDING

  31. Highway 17, Santa Cruz Mountains

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