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mixture of topics > Coastline > Flashcards

Coastline Flashcards

1
Q

What’s mechanical weathering?

A

The break up of rocks without any chemical changes occurring. Usually resulting in piles of rock fragments called scree found at foo of rocky outcrops

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2
Q

Define chemical weathering

A

When a chemical change takes place when weathering occurs. Acidic rainwater slowly dissolve soft rocks such as limestone/chalk. Minerals left behind form clay deposit

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3
Q

What’s biological weathering?

A

The actions of Flora and fauna. Eg: Plant roots grow and expand in rock cracks. Rabbits can burrow into weak rock (i.e: sand)

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4
Q

Freeze - Thaw

A

Water find it’s way into cracks when waves and rain water find their way into cracks. It freezes and thaws as temperatures fluctuate. This process repeats and gradually weakens the rock until sections break away from the cliff face

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5
Q

Mass movement

A

The downhill movement of material under the influence of gravity

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6
Q

Effects of mass movement

A
  • people are evacuated
  • houses/businesses destroyed
  • roads/public services damaged
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7
Q

What is Rockfall?

A

fragments of rock break away from the cliff face (often due to freeze thaw)

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8
Q

What is a landslide?

A

Blocks of rock slide downhill

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9
Q

Mudflow

A

Saturated soil and weak rock flows down a slope

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10
Q

Rotational slip

A

Slump of saturated soil and weak rock along a curved surface

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11
Q

How are waves formed?

A

Waves are a result of wind blowing over the sea. Friction with the surfaces causes ripples to form and these turn into waves.

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12
Q

What does wave energy depend on?

A

It depends on the fetch (the distance which the wind has blown over) , the strength of the wind and the length of time over which the wind has blown

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13
Q

Compare the two types of waves

A 
Constructive
- low in proportion to height
- shape is spilling 
- strong swash, weak backwash
- build up beach 
- summer season
-less than 11 per minute 
Destructive
- high in proportion to length
- shape is plunging
- weak swash, strong backwash!
- erode beach
- winter season
- 13+ per minute
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14
Q

What are the four types of erosion?

A

Hydraulic action
Corrosion
Attrition
Abrasion

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15
Q

Hydraulic action

A

The impact of a wave on a cliff face, air is forced into cracks under high pressure which widens them. Over long periods of time, the growing cracks break parts of the rock off

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16
Q

Corrosion

A

Carbon dioxide in the atmosphere is dissolved into water which causes a weak carbonic acid to form. When the water hits the rocks, this erodes the material. Acidic rain also plays a part in this.

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17
Q

Attrition

A

Beach material is knocked together in the water, which reduces their size and they become smoother and rounder

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18
Q

Abrasion

A

The repeated action of waves breaking on a cliff is enough to remove material from it over time. The sand and shingle in the water acts like sandpaper so erosion takes place faster

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19
Q

What four factors effect coastal erosion?

A

Rock type - some rocks easily erode

Fetch - the larger the fetch the more wave energy..so more erosion

Type of wave - destructive waves have a steep angle of break and have lots of energy

Shape of coastline - certain areas (eg: bays) are more sheltered by headlands so erosion is slower

20
Q

What are the main coastal features caused by erosion?

A

1: headlands and bays
2: caves, arches and stacks
3: wave cut platforms

21
Q

How are headlands and bays formed?

A
  • alternating layers of (non)resistant rock at right angles to the coast
  • less resistant rock erodes quicker which forms a dent in coastline (bay)
  • more resistant rock to the north and South are eroded more slowly hence the coast at theses points protrudes into the sea (headlands)
22
Q

Explain the process of caves, arches and stacks

A

1: the headland is made of resistant rock with natural cracks/ joints in it
2: the breaking waves exploit the cracks and erode them through hydraulic action & corrosion until small caves form
3: the sea continues to erode caves so they get larger. The caves on either side of the headland erode backwards until they meet in the middle to form an arch
4: the sea keeps eroding the arch which becomes larger until the roof collapses and forms a stack
5: the headland retreats and new caves are forming all the time

23
Q

Definition of:

  • cave
  • arch
  • stack
A

Cave - a hollowed out feature at the base of an eroding cliff

Arch - a headland that’s been partly broken through by the sea to form a thin roofed arch

Stack - an isolated pinnacle of rock sticking out of the sea at the end of a headland

24
Q

Explain how a wave cut platform is formed

A

When waves break against the cliff face near the high tide line, the rock is attacked by the processes of erosion which form a wave-cut-notch. Over time and repetition the notch deepens and the overlying cliff collapses under the influence of gravity. Over time the cliff line retreats and extending seawards from the base of the cliff will be a rocky, gently sloping platform called a wave cut platform.

25
Q

What is weathering?

A

The break up and decay of exposed rock at the Earths surface

26
Q

What is longshore drift?

A

The transport of sediment along a stretch of coastline caused by waves approaching the beach at an angle

27
Q

Which direction does backwash flow during longshore drift

A

At right angles to the cliff due to the force of gravity

28
Q

Main landforms of costal deposition

A

1- Beaches
2- Spits
3- Tombolos and Bars

29
Q

What is coastal deposition?

A

When the sea loses energy and deposits sand, rock particles and pebbles that it’s been carrying.

30
Q

When is coastal deposition likely to occur?

A

It’s often associated with constructive waves and is likely to occur when waves enter shallow water or an area of shelter and no wind. This is because it’s the times when waves lose energy

31
Q

What are beaches and what are the main sources of material?

A 
Beaches are made up of material lying between the high & low tide mark. 
Sources:
- cliff erosion
- constructive waves
- longshore drift
32
Q

What is it called when waves enter a bay and mirror the shape of the coastline?

A

Wave refraction

33
Q

What does wave refraction result to?

A

Wave refraction spreads out and reduces wave energy so deposition occurs.

34
Q

What is a tombolo?

A

It’s a spit connecting an island to the mainland. It’s an accumulation of sand and shingle.

35
Q

What is a bar? What feature will it create?

A

And accumulation of sand and shingle (also known as spit) that blocks off a bay or river mouth.

It will create a lagoon around it.

36
Q

Why is the sea level rising and at what rate?

A
  • Global warming!
  • 2mm per year
  • 20 in past century
37
Q

Name some effects of Coastal flooding

A 
Economic:
- loss of tourism
- damage repair 
- loss of agricultural land
Social:
- deaths
- water supplies affected
- loss of housing/businesses (jobs)
Environmental:
- ecosystems affected
- vegetation killed
- increased erosion
38
Q

What’s the cause of cliff collapse?

A

The rocks that make up the cliff are weak and easily eroded by the sea. Also permeable sands sit on impermeable clay which means when water infiltrates into the cliff, it will ‘pond up’ when it reaches the layers of clay. Over time the weight of the cliff increases and so it will collapse.

39
Q

What is

  • hard engineering
  • soft engineering
A

Hard engineering - building artificial structures such as sea walls aimed at controlling natural processes

Soft engineering - a sustainable approach to managing the coast without using artificial structures

40
Q

Examples of hard engineering. What are they

A

Sea wall - curved concrete/rock barrier placed at base of cliffs or top of a beach which reflects the waves back into the sea

Groynes - Timber/rock structures built out to sea from the coast at 90degrees. They trap sediment being moved by LSD. So the beach area is increased

Rock armour - pile of large boulders dumped at foot of cliff. They absorb the waves energy, protecting cliffs

41
Q

Examples of soft engineering. What are they?

A

Beach nourishment - addition of sand to existing beach to make it higher or broader.

Dune regeneration - sand dunes act as buffers to the sea. Marram grass is planted to stabilise them

Marsh creation - Allowing low lying coastal areas to be flooded by the sea to become salt marshes that act as barriers to the sea.

42
Q

Advantages & disadvantages of hard engineering process.

  • sea wall
  • groynes
  • rock armour
A

Sea wall - expensive! (6m per km), looks unnatural but very effective

Groynes - not too expensive (£10,000 each at 200m intervals). Forms bigger beach for tourism:) starve beaches downdrift causing erosion in other places

Rock armour - £1000/4000 per metre. (Quite cheap) easy to maintain. Expensive to transport. Obtrusive

43
Q

Benefits and drawbacks of soft engineering processes

  • beach nourishment
  • dune regeneration
  • marsh creation
A

Beach nourishment - quite cheap (3000 per m), blends in, bigger beach so tourism increase. Needs constant maintenance

Dunes - cheap (2000 per m), natural! Time consuming, damaged by storms

Marsh creation - cheap option, crates habitat for wildlife, farming land is lost

44
Q

Cost of schemes per 1km

A

Sea wall - 6 million
Groynes - 50,000
Rock armour - 1-4 million
Beach nourishment - 3 million

45
Q

How is a salt marsh formed?

A
  • start as accumulation of mud in a sheltered coastal area (eg: behind spit)
  • as more sediment builds up, mud level rises so becomes less covered in water
  • improves fertility of soil
  • plant species colonise (vegetation succession)
46
Q

Describe impacts of sea level rising in maldives

A
  • 350,000 people would evacuate
  • wildlife (180 bird species, 18 dolphin species, 1000 fish species)
  • TOURISM LOSS
  • job losses (fishing community)

mixture of topics (11 decks)

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