Crustal Deformation & Mountain Building

  1. Deformation
    • Deformation is a general term that refers to all changes in the original form and/or size of a rock body.
    • Most crustal deformation occurs along plate margins.
  2. Factors that influence the strength of a rock
    • Temperature
    • Confining Pressure
    • Rock Type
    • Time
  3. Stress
    Force per unit area or the force applied to rocks
  4. Types of directed stresses
    • Compression
    • Tension
    • Shear
  5. Compression
    Action of oppositely directed forces acting towards each other at the same time
  6. Tension
    Action of coinciding and oppositely directed forces acting away from each other.
  7. Shear
    Action of coinciding and oppositely directed forces acting parallel to each other across a surface
  8. Folds
    • Rocks bent into a series of waves
    • Most folds result from compressional forces that shorten and thicken the crust
  9. Types of Folds
    • Anticline
    • Syncline

    Can be symmetrical, asymmetrical, overturned, or plunging.
  10. Anticline
    Upfolded or arched rock layers; a sequence of folded rocks with the oldest rocks on the inside of the fold.
  11. Syncline
    Downfolded rock layers; a sequence of folded rocks with the youngest rocks on the inside of the fold
  12. Symmetrical
    Limbs are mirror images
  13. Asymmetrical
    Limbs are not mirror images
  14. Overturned
    One limb is tilted beyond the vertical
  15. Plunging
    Where folds die out or tilt
  16. Types of Folds - cont'd
    • Dome
    • Circular
    • Oldest
    • Basin
    • Downwarped
    • Youngest
  17. Dome
    Circular or slightly elongated
  18. Circular
    circular displacement of rocks
  19. Oldest
    Oldest rocks in core
  20. Basin
    Circular or slightly elongated
  21. Downwarped
    downwarped displacement of rocks
  22. Youngest
    Youngest rocks in core
  23. Orientation of Deformed Rocks
    • Strike
    • Dip
  24. Strike
    compass direction of an inclined rock layer as it intersects with a horizontal surface
  25. Dip
    Acute angle between the rock layer and the horizontal surface, measured perpendicular to the strike of the inclined rock layer (amount of tilting of the rock layer)
Card Set
Crustal Deformation & Mountain Building
Crustal Deformation & Mountain Building