Folding and Faulting - Summary Notes

Endogenic Processes

• Endogenic processes are formed, located, or occurring beneath the Earth's surface.
• Driven by energy from within the Earth (e.g., volcanism, earthquakes, folding, faulting).

Folds

• Folds occur when the Earth’s crust bends due to compressional forces.
• Types of folds:
  • Symmetrical: Limbs are the same due to equal compression; axial plane is vertical.
  • Asymmetrical: One limb is steeper due to unequal compression; axial plane is tilted.
  • Tight Fold: Sharp-peaked anticline or syncline due to greater compression.
  • Overfold: Rock becomes bent or warped, sometimes overlapping.
  • Recumbent Fold: Compressed so much it is no longer vertical, with significant overlapping.
  • Overthrust Fold: Fold fractures where the axis is pushed over, creating a fracture.
  • Nappe Fold: Extremely overturned, leading to fractured rock layers.
• Parts of a fold:
  • Anticline: Crest of the fold.
  • Syncline: Trough of the fold.
  • Limb (Flank): Sloping side from crest to trough.
  • Axial Plane: Imaginary plane bisecting the vertical angle between equal slopes.
  • Axis: Line that divides the section of the fold.

Faults

• Faults occur when tension, compression, and lateral tears from plate movement cause rock to fracture and displace.
• Types of Faults:
  • Normal Fault: Rocks move away from each other.
  • Reverse Fault: Rocks compress, one plate moves up, the other descends.
  • Tear Fault: (Transform or Strike-Slip Fault): Tectonic plates slide laterally past each other.

Rift Valley (Garben)

• Formed when two normal faults occur parallel to each other, and the land sinks between the faults.

Horst Fault (Block Mountain)

• Land between parallel faults is forced upward because the faults are pushed together.

Importance of Folded and Faulted Landscapes

• Tourism, waterfalls and reservoirs, natural boundaries, defensive sites, biodiversity, geothermal energy, watersheds.