Paper 1 - River Landscapes In The UK Flashcards
What is vertical erosion?
This deepens the river valley (and channel) making it V-shaped.
Its dominant in the upper course of the river.
High turbulence causes the rough, angular particles to be scraped along the river bed, causing more intense downwards erosion.
What is lateral erosion?
This widens the river valley (and channel) during the formation of meanders.
Its dominant in the middle and lower courses.
What are the types of erosion?
Hydraulic action
Abrasion
Attrition
Solution
What is hydraulic action?
The force of the water breaks rock particles away from the river channel.
What is abrasion?
Eroded rock picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion.
What is attrition?
Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges get rounded off as they rub together. The further material travels, the more eroded it gets
What is solution?
River water dissolves some types of rock (e.g - chalk and limestone)
What is traction?
Large particles like boulders are pushed along the river bed by the force of the water.
What is suspension?
Small particles like silt and clay are carried along by the water.
What is saltation?
Pebble sized particles are bounced along the rive bed by the force of the water.
What is deposition?
Its when a river drops the eroded material its transporting.
It happens when rivers slow down.
Why do rivers slow down and deposit material?
The volume of water in the river falls.
The amount of eroded material in the water increases.
The water is shallower (e.g - on the inside of a bed).
The river reaches its mouth.
Where are waterfalls and gorges found?
In the upper course
How do waterfalls form?
- They form where a river flows over an area of hard rock followed by an area of softer rock.
- The softer rock if eroded more than the hard rock, creating a ‘step’ in the river.
- As the water goes over the step it erodes more and more of the softer rock.
- A steep drop is eventually created, which is called a waterfall.
How does a plunge pool form?
The hard rock on a waterfall is eventually undercut by erosion. It becomes unsupported and collapses.
The collapsed rocks are swirled around at the foot of the waterfall where they erode softer rock. This creates a deep plunge pool.
(Also the pressure/force from the falling water)
How does a gorge form?
The waterfall will retreat, leaving behind a steep-sided gorge.
How are meanders formed?
- The current is faster on the outside of the bend because the river channel is deeper (less friction to slow down).
- So more erosion takes place on the outside of the bend, forming river cliffs.
- The current is slower on the inside of the bend, because the river channel is shallower (more friction to slow down).
- So eroded material is deposited on the inside of the bend, forming slip-off slopes.
How are ox-bow lakes formed?
- Erosion causes the outside bends to get closer until there’s only a small bit of land left between the bends (called the neck).
- The river breaks through this land, usually during a flood and the river flows along the shortest course.
- Deposition eventually cuts off the meander forming an ox-bow lake.
What is a flood plain?
Its the wide valley floor on either side of a river which occasionally gets flooded.
What are estuaries?
They’re tidal areas where the river meets the sea.
Where are estuaries found?
They’re found at the mouth of a river, where it meets the sea.
The land is close to sea level and the river valley is at its widest.
What is river discharge?
The volume of water flows in a river per second.
What is peak discharge?
The highest discharge in the period of time you’re looking at.
What is lag time?
The delay between peak rain fall and peak discharge.
