Geo-Mod5

• Outcrop - an exposure of a solid rock on the surface of the earth.
• Folds - defined as undulations or bends or curvatures developed in the rocks
• Folding - the process of development of folds
• Limbs - sides of the fold
• Hinge - found where curvature is maximum
• Axial Surface - hinge line is traced throughout the depth of a folded sequence
• Axial Plane - imaginary plane that passes through all the points of hinge
• Axis of Fold - a line drawn parallel to the hinge line
• Plunge of a Fold - angle of inclination of the fold axis with the horizontal
• Crest and Trough - up arched and down arched bends
• Parts of Folds

  1. Limbs
  2. Hinge
  3. Axial Surface
  4. Axial Plane
  5. Axis of Fold
  6. Plunge of a Fold
  7. Crest and Trough
• Classification of Folds

  1. Anticlines
  2. Synclines
• Anticlines - strata are uparched become convex upward
• Synclines - strata are downarched become convex downward
• Symmetrical Folds - also called as normal or upright folds. The limbs are equal in length.
• Asymmetrical Folds - limbs are unequal in length
• Overturned Folds - folds with inclined axial plane. The amount of dip of the two limbs may or may not be the same
• Isoclinal Folds - group of folds in which all axial planes are essentially parallel
• Recumbent Folds - extreme types of overturned folds in which the axial plane is horizontal
• Parts of Recumbent Folds

  1. Arch
  2. Shell
  3. Core
  4. Root Zone
• Conjugate Folds - a pair of folds that are apparently related to each other may have mutually inclined axial planes
• Box Fold - type of fold with exceptionally flattened top and steeply inclined limbs
• Causes of Folding

  1. Folding Due to Tangential Compression
  2. Folding Due to Intrusions
  3. Folding Due to Differential Compression
• Fault - fractures along which there has been relative movements of the blocks
• Faulting - process of development of fractures and displacement the blocks against each other
• Classification of Faulting

  1. Normal Faults
  2. Reverse Faults
  3. Thrust Faults
  4. Strike-Slip Faults
• Normal Faults - a fault in which hanging wall apparently moved down with respect to footwall
• Reverse Faults - fault which the hanging wall appears to move up with respect to footwall
• Thrust Faults - faults in which the hanging wall has moved up relative to footwall
• Strike-Slip Faults - faults in which faulted blocks have been move against each other
• Joints - defined as divisional planes or fractures along which there has been no relative displacement
• Open Joints - blocks are seperated
• Close Joints - no separation of blocks
• Classification of Joints

  1. Systematic Joints
  2. Nonsystematic Joints
• Systematic Joints - show a distinct regularity in their occurance
• Nonsystematic Joints - these joints do not possess any regularity in their occurance
• Dip Joints - joint sets strike parallel to the direction of the rocks
• Strike Joints - joints sets strike parallel to the strike of the rock
• Oblique Joints - joints where the strike of the joints is at any angle between the dip and the strike
• Tension Joints - developed due to tensile forces acting on the rocks