rivers

Question 1

characteristics of middle course

Answer 1

gradient: medium gradient
valley: asymmetrical valley cross section
channel: deeper/wider river
-smaller/rounded load
-balance between erosion and deposition taking place

Question 2

2 types of erosion that change the cross profile of a river

Answer 2

lateral erosion

vertical erosion

Question 3

what does lateral erosion do

Answer 3

widens the river valley and channel

more dominant in the middle and lower courses of rivers

Question 4

what does vertical erosion do

Answer 4

deepens the river valley and channel making it V shaped

dominant in the upper course

Question 5

how do waterfalls and gorges form?

Answer 5

1. water flows over hard rock followed by soft rock
2. soft rock will erode overtime from abrasion and hydraulic action which forms a waterfall
3. water hits bottom with force which erodes a deep hole —> this is known as a plunge pool
4. soft layer collapses into plunge pool leaving the hard rock undercut (unsupported)
5. hard rock collapse —> process continues creating a steep sided gorge

Question 6

what is a meander

Answer 6

a bend in the river

Question 7

how is a meander formed

Answer 7

1. Water flows fastest on the outer bend of the river where the channel is deeper
2. Erosion takes place on the outside bend, forming river cliffs
3. The inside of the bend of the river is slower because there is more friction so material is deposited
4. Deposited material forms slip off slopes

Question 8

how is an oxbow lake formed?

Answer 8

1. The fastest flow of water is on the outside bend of the river
2. This results in erosion. The outside bends move closer together as the meander neck becomes narrower.
3. When there is a very high discharge, the river cuts across the neck and takes a straight course
4. Deposition eventually cuts off the meander forming an oxbow lake