L1 - The 'Art' of River Erosion

Question 1

How are meanders (middle course) formed?

Answer 1

• Flow of water swings from side to side causing lateral erosion
• This results in the line of water with maximum velocity and power being on the outside, on the inside the water has less energy and deposition occurs causing a gentle sloping bank
• The fast flowing water ricochets onto the opposite side of the river causing erosion again, and deposition on the inside again creating S-shaped rivers called meanders.

Question 2

How do ox-bow lakes form?

Answer 2

• As the meander is forming constant lateral erosion causes the erosion of the insides of two of the s-shapes to continue until they meet
• The river takes the fastest route of flow which is a straight line, not around the bend
• Deposition occurs cutting off the old meander leaving it to become a lake (ox-bow)

Question 3

What are the features of a river in the upper course?

Answer 3

• Lower water quantities and sediment load
• Geology more resistant (harder rock type)
• Rivers have less erosive power.

Question 4

What erosional landform is formed in the upper course?

Answer 4

Interlocking spurs

Question 5

How are interlocking spurs formed?

Answer 5

Rivers travel through the path of least resistance

They flow around the hardest parts of a mountain (spurs), the erosion is downward creating steep v-shaped valleys.

Question 6

How do waterfalls form?

Answer 6

• There is a layer of hard rock and a layer of soft rock as the river travels
• The soft rock is gradually eroded undercutting the hard rock leaving an overhang.
• This creates a plunge poole
• The overhang cannot hold its own weight and collapses creating a waterfall.