Coasts KQ2- How are coastal landforms developed?

Question 1

Define weathering

Answer 1

The in-situ decomposition of rock by chemical, biological, and physical processes

Question 2

What is the effect of an increase of surface area of rock due to physical weathering?

Answer 2

-allows other weathering processes to take place

Question 3

What climatic conditions mean physical weathering has more of an effect?

Answer 3

Large temperature fluctuations

Question 4

Name 4 types of physical weathering

Answer 4

• freeze-thaw
• pressure release
• thermal expansion
• salt crystallisation

Question 5

What causes freeze-thaw weathering?

Answer 5

• water enters cracks in the rock and when it freezes it expands
• the expansion puts pressure on the rock and can enlarge existing joints

Question 6

What is the effect of freeze-thaw weathering?

Answer 6

• even resistant rocks are split

- pieces of rock break off

Question 7

What causes pressure release?

Answer 7

• Overlying rocks are removed by weathering and erosion

- the release of pressure means underlying rock expands and fractures

Question 8

What is the effect of pressure release?

Answer 8

-Parallel fractures are formed

Question 9

What causes thermal expansion?

Answer 9

• rocks experience repeated cycles of temperature change
• when heated rock expands
• when cooled rock contracts

Question 10

What is the effect of thermal exapansion?

Answer 10

Outer layers of rock may crack and flake off

Question 11

What causes salt crystallisation?

Answer 11

• solutions of salts get into rock pores
• salts precipitate and form crystals in pore spaces in rocks
• this causes pressure within the rock

Question 12

What is the effect of salt crystallisation?

Answer 12

Rock disintegrates

Question 13

Which 2 salts are particularly effective at salt crystallisation?

Answer 13

Sodium sulfate and sodium carbonate

Question 14

Name 5 types of chemical weathering

Answer 14

Oxidation
Carbonation
Solution
Hydrolysis
Hydration

Question 15

What causes oxidation?

Answer 15

minerals in rock react with oxygen in air or water

Question 16

What effect does oxidation have?

Answer 16

The original structure of rock is destroyed and disintegrates

Question 17

Which element and type of rock is particularly susceptible to oxidation?

Answer 17

Iron and sandstone

Question 18

What causes carbonation?

Answer 18

• rainwater reacts with dissolved carbon dioxide, forming weak carbonic acid
• The weak acid reacts with calcium carbonate to form calcium bicarbonate
• calcium carbonate is soluble in water

Question 19

What is the effect of carbonation?

Answer 19

Rocks containing CaCO3 are dissolved

Question 20

What causes solution?

Answer 20

-some salts are soluble in water or under specific conditions (e.g iron is only soluble in very acidic water)

Question 21

What is the effect of solution?

Answer 21

Rock minerals dissolve, reducing the size of the rocks. This can sometimes undermine structural integrity

Question 22

Name a type of solution

Answer 22

Carbonation

Question 23

What causes hydrolysis?

Answer 23

Silicates combine with water, reacting chemically to produce clays

Question 24

What is the effect of hydrolysis?

Answer 24

• the secondary minerals formed are softer than the original minerals
• these means the rock is more easily eroded

Question 25

What causes hydration?

Answer 25

- When water molecules react with rocks new minerals - these have a larger volume - this exerts pressure

Question 26

What is the effect of hydration?

Answer 26

surface flaking of rock occurs

Question 27

Name two causes of biological weathering

Answer 27

Tree roots and organic acids

Question 28

How does tree root weathering occur?

Answer 28

- tree roots grow into cracks and exert pressure | - if these trees topple they act as a lever

Question 29

What is the effect of tree roots on rocks?

Answer 29

- pressure exerted on cracks can expand fissures in the rock | - trees toppling bring soils and rock to the surface allowing them to be weathered further

Question 30

How does organic acid weathering (chelation) occur?

Answer 30

- Molluscs secrete acids - The decomposition of plant an animal litter can cause soil water to become acidic - Blue-green algae can also have a weathering effect

Question 31

What is the effect of organic acid weathering?

Answer 31

- Molluscs create small surface hollows in the rock - this increases surface area for other weathering processes - acidic soil reacts with some minerals

Question 32

How does high permeability of rock affect weathering?

Answer 32

- can increase weathering | - as it allows weathering fluids to flow through the rock

Question 33

Does salt crystallisation result from the evaporation of sea water?

Answer 33

Yes

Question 34

Define mass movement

Answer 34

The downslope transportation of material under gravity

Question 35

What is soil creep?

Answer 35

- results from the repeated contraction and expansion of individual soil particles - causes them to very slowly move downwards under gravity

Question 36

What is Mudflow?

Answer 36

- Movement of material downslope in the form of a fluid | - Material on a slope becomes saturated with water, making it much heavier

Question 37

Under what conditions do mudflows usually occur?

Answer 37

- after a period of intense rainfall | - areas that have thin soils overlying impermeable bedrock

Question 38

Under what conditions do rock slides usually occur?

Answer 38

-rocks that have jointing or bedding planes roughly parallel to the angle of the slope

Question 39

Under what conditions do rock falls usually occur?

Answer 39

-on slopes in excess of 40 degrees

Question 40

What can prompt rock falls to occur?

Answer 40

- extreme physical or chemical weathering - storm action - Earthquakes

Question 41

What signs can point to rock falls having occurred on a cliff?

Answer 41

A tallus/scree slope at the foot of the cliff

Question 42

Under what conditions does rotational slumping usually occur?

Answer 42

-When weaker rocks/clays overlie more resistant impermeable rocks

Question 43

What signs can point to slumping having occurred on a cliff?

Answer 43

The presence of a recurved slip plane

Question 44

Name the 5 wave action processes

Answer 44

``` Abrasion Attrition Hydraulic action Pounding Solution ```

Question 45

Which are the two most significant processes?

Answer 45

Pounding and hydraulic action

Question 46

What is abrasion?

Answer 46

Water containing rock particles scour the coastline (rock rubbing against rock)

Question 47

What is attrition?

Answer 47

Rock particles transported by wave action, collide with each other and become worn away, smaller, and rounder

Question 48

What is hydraulic action?

Answer 48

- When waves break against the cliff face air and water trapped in cracks and crevices becomes compressed - as the water recedes pressure is released and the air and water expands - this widens the crack

Question 49

What is pounding?

Answer 49

The mass of a breaking wave exerts pressure on the rock, weakening it

Question 50

What is solution?

Answer 50

Minerals are dissolved by water, this is limited by the quantity of minerals in the rock

Question 51

Give an example of a mineral dissolved in sea water

Answer 51

Magnesium carbonate