| Front | Erosion |
| Back | The process of wearing away soil and rock |
| Front | Waterfall formation |
| Back | River flows over an area of more/less resistant rock -> the soft rock is eroded more easily, causing it to erode away beneath the hard rock -> as soft rock is eroded an overhang is formed -> corrosion and hydraulic power weaken the rock -> the rotational movement of water quickens erosion + water falls vertically, gaining kinetic energy and exerting force at the base -> creating a plunge pool -> due to gravity, the overhang collapses -> this process is repeated and the waterfall retreats upstream -> river retreat can lead to the formation of a gorge Examples: Niagra Falls - America |
| Front | Traction |
| Back | the movement of larger rocks and pebbles through water rolling them along the river bed |