1. Softer rock is cut back from the erosion, due to the splash back hitting the plunge pool.
2. Due to under cutting the overhang will collapse under gravity. Hydraulic action and corrasion.
3. Waterfall retreats upstream to form a gorge.
The plunge pool is created by the force of water hitting the less resistant rock below and deepened by corrasion (rocks rubbing against the bed).
IN AN EXAM:
TYPES OF WATERFALL: