Folding and Faulting
Understanding Earth's Crustal Deformation
Folding and faulting show how rocks respond to pressure inside the Earth's crust. In this topic, learners need to recognise the forces involved, the landforms produced, and South African examples such as the Cape Fold Mountains.
Folding
Folding occurs when rock layers are subjected to compressional forces, causing them to bend rather than break. This typically happens deep underground where heat makes rock more plastic.
Key Features of Folding
Anticline
Upward, arch-like fold - the "peak" of the fold.
Syncline
Downward, U-shaped fold - resembling a "valley".
Limbs: The sides of folds, which can vary in steepness and length.
Types of Folds
Symmetrical Folds
Evenly balanced limbs, uniform appearance.
Asymmetrical Folds
Uneven limbs, lopsided appearance.
Overfolded Folds
Pushed beyond normal limits - complex structures.
Recumbent Folds
Layers pushed over completely - nearly horizontal.
Faulting
Faulting occurs when the Earth's crust experiences so much stress that it fractures and moves. This typically happens closer to the surface where rocks are more brittle.
Types of Faults
Normal Fault
Caused by tension - crust pulled apart. One block slides down.
Reverse Fault
Caused by compression - crust pushed together. One block thrust up.
Lateral (Strike-slip) Fault
Caused by shearing - horizontal movement, blocks slide past.
Resulting Landforms
Rift Valley (Graben)
A long, narrow valley formed when a block of land sinks between two parallel faults.
Block Mountain (Horst)
A block of land pushed up or remains elevated while surrounding land sinks.
Pro-Tip for Exams
Folding: Look for parallel ridges in contour lines on topographic maps.
Faulting: Look for steep "cliffs" or escarpments where land drops suddenly.
Practice & Assess
Six interactive games - all reset buttons work
Quiz 1 - Fold Types
Which fold has evenly balanced limbs?
Quiz 2 - True/False
"Normal faults are caused by compression."
Match - Fold Features
Fill - Upward Fold
Fill - Rift Valley
Order - Fault Types
Arrange: Normal, Reverse, Lateral (click to reorder)
Key Terms
Key Recap
For revision, focus on the difference between folding and faulting: folded rocks bend, while faulted rocks break and move. You should also be able to link each process to the landforms it produces, such as fold mountains, horsts, and grabens.
