Erosional landforms
The processes of erosionThe wearing away of pieces of rock, soil or other solid materials. can create different landforms. The erosional features are often found in the upper courseThe highest section of a river located in the mountains. of the river.
Waterfalls and gorges (Large scale landforms)
A waterfallA steep drop in a river. is a sudden drop along the river course. It forms when there are horizontal bands of resistant rock (hard rock) positioned over exposed, less resistant rock (soft rock).
- The soft rock is eroded quicker than the hard rock and this creates a step.
- As erosion continues, the hard rock is undercut forming an overhang.
- abrasionWhen rocks carried by the sea water wear away the landscape, eg cliff face/headland. and hydraulic actionErosion caused by the force of river water hitting cracks in the side of the river bank. The air in the cracks becomes compressed and then explodes outwards, breaking off bits of rock. continue to erode the soft rock to create a plunge poolThe pool of water found at the bottom of a waterfall. It is an erosional feature which has been created by a combination of hydraulic action and the abrasion of the plunging water. (small scale landform).
- Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
- This process continues and the waterfall retreats upstream.
- A steep-sided valley is left where the waterfall once was. This is called a gorgeA deep, narrow passage that usually has a river running through it..
V-shaped valleys
In the upper course there is more vertical erosion as the river is less powerful, so material cannot be moved in suspensionA mixture of two substances, one of which is finely divided throughout the other. and is instead moved along the river bed using traction or saltation. This erosion, together with the movement of weathered material at the sides of the river, creates the classic V-shaped valley. If there are areas of hard rock which are harder to erode, the river will bend around them.