Rivers Flashcards
What is hydraulic action in rivers?
The force of the water colliding with rocks, the river bed or river bank which slowly erodes it away
What is abrasion?
Eroded rocks picked up by the water which scrape and rub against the river bank and river bed and wears it away
What is attrition?
When eroded rocks collide with each other making them smoother and rounder
What is traction?
Where larger load (Material) is pushed along the river bed (Boulders)
What is saltation?
A bouncing action where lighter load is bounced along the river bed
What is suspension?
Where the lightest load is suspended/carried by the water in the river
What is solution?
Erosion: When the river dissolves the material (e.g limestone and chalk)
Transport: Where soluble materials are dissolved by the water
What is deposition?
Deposition is when a river puts down the material it is carrying
Why does deposition happen?
When the river loses energy
When the volume of the water falls
When the water is shallow
When the river reaches the mouth
Inside of meanders
What are interlocking spurs (See rg for image)
Resistant rock that sticks out
The river can’t erode this rock as it isn’t powerful enough meaning it winds around them
Found in the upper course
Definition: High land that alternates between either side of the valley
How are waterfalls formed?
When the river flows over different bands of rock
These are normally found in the UPPER course
It is where there is softer rock underneath the cap rock (Rock at the top of the waterfall)
What is a gorge and how is it formed?
Gorges are found in the UPPER course
A gorge is is where the waterfall has retreated
Over time the soft rock is eroded quicker than the cap rock on top of it because of differential erosion by abrasion and hydraulic action
This creates and overhang (Ledge)
Because of the force of gravity and the weight of the water the overhang will eventually collapse falling into the plunge pool
The rock breaks apart and because of abrasion and hydraulic action the plunge pool widens and deepens
This process repeats and the waterfall retreats forming a gorge
What are the properties of a waterfall?
Steep drop
Free flowing water
Plunge pool
What are the properties of a gorge?
Narrow steep valley sides
Turbulent river flow
Downstream (in front of) a waterfall
How is a meander formed?
A meander is typically found in the MIDDLE and LOWER course
A meander is formed when the river deposition happens on the inside of a bend whereas abrasion and hydraulic action happen on the outside of the bend.
