1. Unit 2: River Landscapes How are Waterfalls formed?

2. A sudden and often vertical drop of a river along its course
What is a WATERFALL?
A sudden and often vertical drop of a river along its course

3. A narrow, steep-sided valley
What is a GORGE?
A narrow, steep-sided valley

6. Waterfall formation

7. Water flows over a hard rock onto a softer rock
Processes of erosion (especially abrasion and hydraulic action) erode the softer rock quicker because there is less resistance.
This causes the soft rock to be undercut (1), leaving an overhang above.
This overhang is unsupported and due to gravity it collapses into the river (2). The rocks this add to the water leads to more abrasion creating Plunge Pool (3).
This sequence is repeated over and over meaning the waterfall retreats upstream (4) and creating a steep sided gorge in the valley (5).