Rivers

Question 1

What is the path of a river called?

Answer 1

The course.

Question 2

What are the 3 parts to the course of a river?

Answer 2

Upper, middle and lower.

Question 3

What does a river form as it flows downhill?

Answer 3

Channels and valleys.

Question 4

What and how do they erode?

Answer 4

They erode the landscape by wearing it down and transporting the material elsewhere, where it is deposited.

Question 5

What does the long profile of the river show?

Answer 5

How the gradient changes over the course.

Question 6

What does the cross profile show?

Answer 6

What the river’s cross section looks like.

Question 7

What is the upper course’s gradient and what is its valley and channel shape?

Answer 7

The gradient is steep, and it has a V - shaped valley with steep sides and a narrow, shallow channel.

Question 8

What is the middle course’s gradient and it’s valley and channel shape?

Answer 8

The gradient is medium and the valley has gently sloping sides. The channel is wider and deeper.

Question 9

What is the lower course’s gradient and what is its valley and channel shape?

Answer 9

The gradient is gentle. The valley is very wide and almost flat. The channel is very wide and deep.

Question 10

What causes vertical erosion?

Answer 10

High turbulence causes rough, angular particles to be scraped along the river bed.

Question 11

What is lateral erosion and where is it dominant?

Answer 11

This widens the river valley and channel during the formation of meanders. It is dominant in the middle and lower course.

Question 12

What affects river valleys ( weathering)?

Answer 12

Chemical and biological weathering.

Question 13

What does weathering do?

Answer 13

It breaks down rocks on the valley side.

Question 14

What type of weathering is freeze-thaw?

Answer 14

Mechanical.

Question 15

What is the process of freeze-thaw?

Answer 15

When temperatures alternate above and below 0*, water gets into rocks with cracks. When it freezes it expands and when it melts it contracts, putting alternating pressure on the rock. As this repeats, the crack widens and causes the rock to break.

Question 16

What are the 4 processes of erosion?

Answer 16

Hydraulic action.
Abrasion.
Attrition.
Solution.

Question 17

What is hydraulic action?

Answer 17

The force of weathering breaking rock particles away from the river channel.

Question 18

What is abrasion?

Answer 18

Eroded rocks that are picked up by the river wear away the channel by being scraped against it. This how the most erosion occurs.

Question 19

What is attrition?

Answer 19

Eroded rocks smash into each other, breaking them into smaller segments. Their edges are rounded off. The further material travels, the more eroded it becomes, decreasing particle size along the course of the river.

Question 20

What is solution?

Answer 20

Water dissolving a rock type such as chalk.

Question 21

What is traction?

Answer 21

Large particles being pushed across the river bed by the force of the water.

Question 22

What is suspension?

Answer 22

Small particles carried by the water.

Question 23

What is saltation?

Answer 23

Smaller rocks (pebble size) bouncing along the river bed by the force of the water.

Question 24

What is solution?

Answer 24

Soluble materials dissolving and being carried by the water.

Question 25

What is transportation?

Answer 25

The movement of eroded material.

Question 26

What is deposition?

Answer 26

When a river drops eroded material.

Question 27

What are the four reasons why rivers slow and deposit material?

Answer 27

The VOLUME falls.
The AMOUNT of eroded material increases.
The water is SHALLOWER.
The river reaches the MOUTH.

Question 28

Where are waterfalls and gorges found?

Answer 28

In the upper course of a river.

Question 29

How is a waterfall formed?

Answer 29

1) They form where HARD ROCK is followed by SOFT ROCK.
2) SOFT ROCK is eroded more than the hard rock by HYDRAULIC ACTION and ABRASION, creating a ‘STEP’.
3) From the step a DROP is created. This is called a WATERFALL.

Question 30

How is a gorge created?

Answer 30

1) Eventually the hard rock under a waterfall is ERODED. It collapses.
2) These rocks fall under the waterfall, where they erode the SOFTER ROCK by ABRASION, creating a PLUNGE POOL.
3) More EROSION causes more UNDERCUTTING and COLLAPSES. This makes the waterfall RETREAT, leaving a steep-sided GORGE.

Question 31

Where and how do interlocking spurs occur?

Answer 31

In the upper course of the river, vertical erosion causes steep, V-shapes valleys to form that wind around hillsides because they’re too weak to laterally erode them. This makes the hillsides interlock, hence interlocking spurs.

Question 32

Where are meanders?

Answer 32

The middle and lower course.

Question 33

How is a meander formed?

Answer 33

1) The CURRENT is FASTER on the OUTSIDE of the channel because it’s deeper.
2) More EROSION (hydraulic action and abrasion) takes place on the OUTSIDE of the bend. This forms RIVER CLIFFS.
3) The CURRENT is SLOWER INSIDE the bend because it’s shallower so there is more friction.
4) Eroded material is DEPOSITED on the INSIDE, forming SLIP-OFF SLOPES. This creates a meander!

Question 34

What are oxbow lakes formed from?

Answer 34

Meanders.

Question 35

How are oxbow lakes formed?

Answer 35

1) EROSION causes the OUTSIDE bends to get CLOSER.
2) This leaves a small bit of land between them, called the NECK.
3) The river breaks the neck, usually during a flood.
4) The river flows along the SHORTEST course.
5) DEPOSITION cuts off the meander, forming an oxbow lake.