GCSE Geography > Coasts (Waves) > Flashcards

Coasts (Waves) Flashcards

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1
Q

How are waves caused?

A

the transfer of energy from the wind to the sea, due to the friction of the wind blowing over the surface of the water. As waves approach a beach, the shoreline becomes shallower and allows the waves to break up on the beach.

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2
Q

What does the amount of energy in a wave depend on?

A
  • the speed of the wind (more energy is transferred)
  • how long the wind has been blowing (more power)
  • the fetch (can build up power)
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3
Q

What is the fetch?

A

the length of water over which a wind has blown without obstruction

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4
Q

Where is the longest fetch in the UK?

A

Extends 3000 miles from Brazil in the South West, which coincides with the prevailing wind direction and high energy waves in the South West

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5
Q

What are the 2 types of waves?

A

Constructive and destructive

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6
Q

What do constructive waves do?

A

build the beach up through the process of deposition

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7
Q

What do destructive waves do?

A

destroy the beach through the process of erosion

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8
Q

Where are constructive waves found?

A

Sheltered bays where they build up sandy beaches and are common in summer

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9
Q

How do constructive waves work?

A

the swash spills forwards over the beach, covering a large area, and loses energy as it is in friction with the sand. Its swash is stronger than its backswash

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10
Q

Where are destructive waves found?

A

more exposed bays, where they build up pebble beaches, and are more common in winter

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11
Q

Describe a destructive wave’s swash and backwash

A

although its swash is much larger than that of a constructive wave, relatively, its backwash is much stronger than its swash

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12
Q

How do destructive waves work?

A

they comb beach material back into the sea, and the force generated by a breaking wave is enough to erode a headland

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13
Q

Describe the wave height, length and frequency of a constructive wave

A

Height: low (<1m)
Length: long
Frequency: low (8-10 waves per minute)

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14
Q

Describe the wave height, length and frequency of a destructive wave

A

Height: high (>1m)
Length: short
Frequency: high (10-14 waves per minute)

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15
Q

What is coastal erosion?

A

A natural process that happens when land and sediment are worn away by waves, currents and storms, and can cause the coastline to change over time. It can also be caused by wind and water wearing away at rocks

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16
Q

Describe one-way coastal erosion

A

when waves hit a cliff and push air into cracks, causing the rock to break apart. Or when loose pieces of rock collide with each other, making them smaller and smoother.

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17
Q

What formations can erosion create?

A
  • tunnels
  • bridges
  • columns
  • pillars
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18
Q

What is the difference in how soft and hard rocks erode?

A

Soft rocks erode faster
hard rocks erode slower, and this can make the coastline uneven

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19
Q

What are the key factors which affect coastlines?

A
  • the rock type/geology
  • the fetch of the wave
  • the angle of the slope
  • weather conditions
  • the amount of vegetation (stabliises slopes)
  • the amount of human interference (can protect or be a concern)
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20
Q

Name 3 ways humans could make coastlines more susceptible to natural processes?

A
  • sea walls
  • urbanisation/living on coastlines
  • pollution/contamination
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21
Q

How does geology influence the coastline?

A
  • the way layers of rock are folded or tilted
  • faults are cracks in rocks
  • enormous tectonic pressure can cause rocks to snap rather than fold/bend and movement happens either side of the fault
  • faults form lines of weakness in rocks and are easily carved out by the sea forming landforms
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22
Q

What are the 3 types of rock?

A

sedimentary
metamorphic
igneous

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23
Q

Describe sedimentary rocks and include examples

A
  • rocks formed from sediments settled the bottom of a large body of water, and have been compressed over millions of years.
    ex. limestone, sandstone
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24
Q

Describe igneous rocks and include examples

A

volcanic rocks formed when magma cools and crystalizes either at the surface of the earth (extrusive) or within the earth (intrusive)
ex. basalt, granite

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25
Name two soft rocks and two hard rocks
soft: chalk, sandstone hard: basalt, slate
26
Describe metamorphic rocks and include examples
sedimentary or igneous rock that has been subjected to severe heat or pressure changing its structure ex. Slate, marble
27
Describe less resistant rocks
they have less structural strength and are eroded easily. they typically produce lower cliff profiles that experience mass movement
28
What is a concordant coastline?
if the rock beds run parallel to the edge of the sea, and can be identified by high cliffs and coves
29
What is a discordant coastline?
if the rock beds run perpendicular to the sea's edge, and can be identified by headlands and bays
30
what are bedding planes?
cracks in hard rock, where the air is compressed by wave action, and as the cracks widen erosion occurs as they are forced apart
31
how do you prevent bedding planes?
build groynes to preserve the beach but the further shoreline is left vulnerable to erosion due to lack of sand, and cliffs form which are more exposed to erosion
32
Define weathering
the on the spot (in situ) breakdown of rocks at the Earth's surface, and does not involve the removal of rock material
33
What are the 2 types of weathering?
chemical and mechanical
34
Describe mechanical weathering
describes the process of rocks crumbling or disintegrating, and is usually associated with extremes of temperature
35
Describe freeze thaw (a type of mechanical weathering) and where it occurs
1. water collects in rock crack 2. water freezes and expands forcing the cracks to widen 3. the ice thaws, contracts, and water gets deeper into the cracks again 4. the repeated expansion and contraction causes further cracks until the rock splits (it occurs in cold climates)
36
What is chemical weathering?
requires a chemical reaction to take place - most often through the effects of rain and the sea water being slightly acidic, whcih wears away the rock over time, often through dissolving it.
37
Describe carbonation (a type of chemical weathering)
carbonic acid in rainwater reacts with calcium carbonate in limestone and chalk to form calcium bicarbonate. This is soluble and is washed away in solution
38
Describe hydrolysis (a type of chemical weathering)
water reacts with the rock and alters the size and chemical composition of the minerals, making them less resistant to weathering
39
Describe oxidation ( a type of chemical weathering)
oxygen reacts with any iron minerals in the rock to form iron oxide (rust) . iron oxide is much more fragile than iron, so the weathered region becomes much weaker
40
Define erosion
the wearing away and removal of material from the coast by the waves
41
What is hydraulic action?
a method of erosion - the relentless force of waves pounding against the cliffs. This causes water and air to be forced into cracks in the rock, weakening it
42
What can weathering processes do to the coastline?
weaken it more susceptible to erosion impact people living on the coast
43
What is abrasion?
material is thrown at the cliffs, scratching and scrapping the surface away
44
What is attrition?
rocks carried in the waves knock into eachother, making them smaller, smoother and rounder
45
What is solution?
dissolution od calcium based rocks in slightly acidic sea water
46
How is material transported by waves?
a process known as longshore drift, which is determined by the prevailing wind
47
What is traction?
where pebbles, and larger materials are rolled along the sea bed
48
What is saltation?
where smaller pieces of shingle or large sand grains are bounced along the sea bed
49
What is suspension?
small particles such as silts and clays are suspended in the flow of water
50
What is solution (#2)?
when minerals in rock like chalk and limestone are dissolved in sea water and then carried along in the water in solution (the load is invisible)
51
How can people affect longshore drift?
management in , such as hard and soft engineering and groynes
52
Why is material deposited along the coastline?
when the waves lose energy , it drops the material known as deposition
53
When does deposition occur?
1. waves enter a bay or sheltered area 2. waves enter shallower water and slow down 3. there is little wind, reducing the energy of the waves 4. there is too much material, known as heavy load
54
What order will the material be deposited in?
1. boulders 2. pebbles 3. finer sands
55
define mass movement
the downslope movement of soil or mud under the influence of gravity, often triggered by heavy rainfall
56
What are the 3 types of mass movement?
sliding slumping rock falls
57
Describe rock slides
- occurs on steep cliffs - previously weakened by weathering - heavy rain soaks into soil and travels down into rock below - saturated rock slides along a straight slip plane, where rock falls as a large block, maintaining contact with cliff - leading edge collects as pile of rocks at bottom, known as scree
58
Describe mud slides
- wet, rapid and tend to occur on steep slopes (over 10 degrees) - vegetation cover is sparse, so there are fewer roots to hold soil in place - happen after heavy rain - soil is lubricated and can overcome gravity and slide - at base, saturated soil spreads out to make a lobe
59
Describe rock falls
- vertical cliffs - lots of joints and cracks - prone to freeze-thaw weathering - at bottom of cliff , fallen debris forms scree slope - sudden and rapid
60
Describe a slump (a type of rock fall)
a concave (curved) slip plane so material is rotated backwards into cliff face as it slips - common on cliffs made of softer material - repeated slumping can create a stepped cliff profile
61
How are mass movement and weathering different?
weathering is weakening of rock over years, mass movement is transportation of rock and can be very sudden and rapid
62
How are erosional landforms created?
erosional processes wear away land along the coastline and can be sudden or very slow
63
What is a headland?
an area of hard rock, resistant to erosion
64
Where are headlands created?
On discordant coastlines
65
How are headlands and bays formed?
- soft rock is eroded first - forms bays - waves enter bays and change shape to do so (wave refraction) - slow down and deposit sediment to form beaches - hard rock sticks out to form headlands - become vulnerable to erosion - waves are concentrated on them
66
Describe how caves are formed
- headland is vulnerable - waves attack cracks - cracks enlarged through hydraulic action and abrasion
67
Describe how arches are formed
- cave is further eroded through HA and abrasion, making it higher and deeper - an arch is formed by sea cutting through to other side of headland
68
Describe how stacks are formed
- sea erodes bottom of arch over time making it wider - roof or arch no longer supported as its too heavy - collapses to create stack
69
Describe how stumps are formed
- stack gets undercut over time - top of stack collapses - left with a stump
70
what is a cliff?
a vertical or nearly vertical rock exposure (base is most vulnerable to erosion)
71
What does rate of recession of a cliff depend on?
the hardness of the rock (soft rock cliffs are prone to slumping) (hard cliffs create high cliffs and wave cut platforms)
72
What is a wave cut platform?
the narrow, flat rocky slope often found at the base of a sea cliff
73
Which erosion process if not going to erode a cliff?
attrition
74
a chalk cliff face is most likely to be eroded by?
solution, as its calcium based
75
which two processes of erosion get worse during a storm?
hydraulic action and abrasion
76
describe how a wave cut platform is formed
1. at low tide, there is no erosion at the base of the cliff 2. at high tide, base of cliff is eroded and becomes a notch , and gets bigger as more erosion occurs as each high tide 3. weaknesses in the cliff show as notch gets bigger. Rock overhangs and is unstable 4. overhang is too heavy and collapses under its own weight 5. collapsed material falls to base of cliff and cliff face is retreated. Wave cut platform left 6. fallen material erodes notch at base of cliff 7. process repeats
77
How might a wave cut platform be further eroded through abrasion?
rocks may beat against the bottom
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