Rivers Flashcards
Hydraulic action
The sheer power of the water as it smashes against the riverbanks. Air becomes trapped in the cracks of the riverbank and bed, and causes the rock to break apart.
Abrasion
When pebbles grind along the riverbank and bed in a sandpapering effect.
Attrition
When rocks that the river is carrying, knock against each other. They break apart to become smaller and more rounded.
Solution- erosion
When the water dissolves certain types of rocks, for example, limestone.
Traction
Large heavy pebbles are rolled along the river bed. This is the most common near the source of a river as here the load is larger.
Saltation
Pebbles are bounced along the river bed, most commonly near the source.
Suspension
Lighter sediment is suspended (carried) within the water, most commonly near the mouth of the river
Solution (transportation)
The transport of dissolved chemicals. This varies along the river, depending on the presence of soluble rocks.
Deposition + its factors
When a river loses energy and drops any material/sediment which it has been carrying
Shallow water
At the rivers mouth
When the volume of the water decreases
Vertical erosion
When the land is eroded or worn away in a downwards direction.
Lateral erosion
Wearing away of the landscape when a river erodes sideways
What happens at a river’s upper course
Where the river starts
Upland area - steep gradient
The load is large as it hasn’t been broken down by erosion yet. - hard and impermeable
Vertical erosion
What happens at a river’s middle course
-gentle gradient
Lateral erosion
Transportation
What happens at a river’s lower course
Low gradient
Deposition
Some lateral erosion
How is waterfall and gorge formed
Hard rock is over a layer of soft rock
Soft rock is eroded, leaving an overhang of hard rock
A plunge pool forms with fallen rocks
The waterfall retreats and leaves a steep sided gorge
