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Flashcards in Weathering And The River Valley Deck (20):
0

How are rocks in a drainage basin broken down?

Weathering

1

What is weathering?

The breakdown of rocks where they are

2

What are the main types of weathering?

Mechanical, chemical and biological

3

What is mechanical weathering?

The breakdown of rock without changing its chemical composition

4

Freeze-thaw weathering = mechanical weathering. What happens?

Temperature alternates above and below 0
Water gets into cracks in rock
Water freezes and expands - pressure
Water thaws and contracts - releases pressure
Repeated freezing and thawing - cracks widen - rock breaks

5

What is chemical weathering?

Breakdown of rock by changing its chemical composition

6

Carbonation weathering = chemical weathering. What happens?

Rain water contains CO2 - weak carbonic acid - reacts with rock that contains calcium carbonate - rocks dissolved by rainwater

7

What is biological weathering?

Breakdown of rocks by living things

8

An example of biological weathering

Plant roots grow into cracks and push cracks apart - rock breaks

9

What is the path of a river as it flows downhill called?

Course

10

The upper course is closest to the...

Source of the river

11

The middle and lower course are closest to the...

Mouth of the river

12

Rivers flow in channels...

In valleys

13

What do rivers do?

Erode landscape - wear it down
Transport material to somewhere else - then deposit it

14

What causes the shape of the valley and channel to change along the river?

Erosion or deposition - whichever has the most impact

15

What does the long profile of a river show?

How the gradient changes over different courses

16

What does the cross profile of a river show?

What a cross-section of the river looks like

17

What is the upper course gradient and valley and channel shape like?

Gradient - steep
Valley shape - v shaped, steep sides
Channel shape - narrow and shallow

18

What is the middle course gradient and valley and channel shape like?

Gradient - medium
Valley shape - gently sloping
Channel sides - wider and deeper

19

What is the lower course gradient and valley and channel shape like?

Gradient - gentle
Valley shape - very wide, almost flat
Channel shape - very wide, deep