Please enable JavaScript.
Coggle requires JavaScript to display documents.
GCSE Geography: Fluvial processes and landscapes - Coggle Diagram
GCSE Geography:
Fluvial processes and landscapes
Fluvial processes
Erosion
Abrasion
: The load carried by the river hits the bed or banks, dislodging particles.
Attrition
: stones carried by the river knock against each other, becoming smaller/more rounded.
Solution
: Alkaline rocks e.g. limestone are dissolved by slightly acidic river water.
Hydraulic action
: The force of water hitting the river bed and banks. Most effective when water is moving fast and at high volume.
Can be vertical (downwards) or lateral (horizontally)
Transportation
Solution
: dissolved load.
Suspension
: Small sediment held in the river.
Traction
: Large particles rolled on river bed.
Saltation
: 'Bouncing' of particles too heavy to be suspended.
Load
: material transported by a river.
Deposition
Larger rocks tend to be deposited in the upper course of a river. Only transported a very short distance, mostly by traction during periods of very high flow.
Finer sediment is carried further downstream, mostly in suspension. Will be deposited on river bed or banks, where velocity is slowed by friction.
Occurs when velocity of a river decreases. No longer has energy to transport sediment so it is deposited.
A large mount of deposition at the river mouth, where interaction with tides, along a very gentle gradient, reduces river velocity.
Fluvial landscapes
V-shaped valley and interlocking spurs
Formation:
1) In the upper course of the river hydraulic action is used to deepen the channel by vertical erosion.
2) Freeze-thaw weathering widens the channel, giving it a v-shaped cross profile. The river removes the rocks that have fallen off the sides of the valley.
3) As the river widens it takes the easiest path by avoiding the hard rocks interlocking spurs are made of so they enter the valley at opposite sides.
Waterfalls
Formation:
1) A river flows over hard rock with soft rock underneath.
2) The softer rock is eroded faster by the process of hydraulic action which is when the force of the water exerts great pressure on the cracks in the rocks causing them to widen and the rock breaks away.
3) undercutting by hydraulic action and abrasion which is when the load carried by the water is forced into the river bed causing rock to be worn away, leaves the harder unsupported rock to collapse into the plunge pool below.
4) The waterfall moves backwards cutting a gorge as the previous steps repeat themselves.
Gorges
Characteristics:
very narrow, steep valley
located immediately downstream of a waterfall
river channel takes up most of the valley floor
turbulent fast flowing white water
many areas of bare rock on valley sides
boulders litter valley floor
Formation:
Once a waterfall in formed it starts to retreat upstream and leaves a valley behind. Every time the overhanging cap rock breaks off the gorge retreats further and grows longer.