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geography > Coastal Landscapes- waves, landforms, trasnport > Flashcards

Coastal Landscapes- waves, landforms, trasnport Flashcards

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1
Q

How are waves created

A

through friction between wind and water surface

-transfers energy from win into water- generating ripples which grow into waves

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2
Q

What is wavelength

A

horizontal distance from crest to crest

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3
Q

What is wave frequency

A

number of waves [passing a particular point over given period of time

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4
Q

Name 4 factors affecting wave size

A
  • wind strength
  • duration wind blows
  • water depth
  • wave fetch
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5
Q

Describe the 4 steps that occur when waves approach the coast

A
  • water becomes shallower- circular orbit of water particles change to elliptical shape
  • wavelength, velocity decrease, wave height increases
  • force pushes wave higher before spilling and breaking on shore
  • water rushes up beach as swash and flows back as backwash
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6
Q

Describe constructive waves

A
  • low energy waves
  • low wave height
  • long wave length
  • low wave frequency
    -strong swash, weak backwash
  • strong swash pushes sediment up beach, depositing it as a (berm/ridge of sediment) at top of beach
    -depositional
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7
Q

Describe destructive waves

A
  • strong backwash, weak swash
    -high wave height
    -short wavelength
    -high frquency
    -erosional

-strong backwash- erodes
beach material and carries it offshore, creating offshore ridge

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8
Q

What is beach morphology

A

shape of the beach- width, slope, features, such as berms, ridges and runnels. It also includes the type of sediment found at different locations

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9
Q

What is a beach sediment profile

A

pattern of distribution of different size/ shaped deposited material

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10
Q

How does constructive waves alter beach morphology and sediment profile

A
  • cause movement of sediment up beach- steeping beach profile
  • produce berms (ridges of material) at point where swash reaches high tide
  • leads to sorting of material- heavier shingle at back of beach, sand closer to sea
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11
Q

How does destructive waves alter beach morphology and sediment profile

A
  • berms eroded by plunging waves, high-energy swash
  • strong backwash transports sediment offshore

-

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12
Q

In which seasons are constructive waves dominant

A

-summer

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13
Q

In which seasons are destructive waves dominant

A

-winter

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14
Q

Explain daily variations in terms of contructive and destructive waves

A

-destructive waves change to constructive ones as the wind drops

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15
Q

What are the four different types of wave type that influences beach morphology

A
  • Hydraulic Action
  • Corrosion
  • Abrasion
  • Attrition
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16
Q

How does wave type and wave size influence erosion

A
  • most erosion occurs during winter- when destructive waves are largest and powerful
  • hydraulic action, abrasion, powerfully attack differences in rock resistance and weaknesses
  • faster when wind is blowing directly onshore
  • fastest when tide is high
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17
Q

How does lithology influence erosion

A
  • any rock with weaknesses (joints, faults, bedding planes)
  • result in formation of landscapes
  • bands of more resistant rock between weaker joints and cracks erode slower
  • fastest when rocks forming coastline are weaker
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18
Q

What is hydraulic action

A

Waves crash against rocks and compress air in the cracks, adding pressure. Repeated compression widens the cracks and causes rocks to shatter

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19
Q

What is corrosion

A

Water dissolves minerals in the rocks (particularly limestone-> carbonate rock) and washes it away

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20
Q

What is abrasion

A

Sediment picked up by breaking waves is thrown against the cliff face
The sediment acts like a tool on the cliff – chiselling away at the surface and gradually wearing it down

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21
Q

What is attrition

A

Eroded particles in the water collide with each other and break into smaller fragments

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22
Q

Name 5 erosional landforms

A
  • blowhole
  • retreating cliffs
  • cave-arch-stack-stump seqeunce
  • wave-cut notch
  • wave-cut platform
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23
Q

What is a wave-cut notch

A

curved indentation (1-2m high) extending along base of cliff

-forms between high tide and low tide -> destructive waves

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24
Q

What is a wave-cut platform

A

flat rock surface exposed at low tide extending out to sea from base of cliff

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25
Q

How does a wave-cut platform form

A
  • hydraulic action, abrasion at high and low tide mark form wave-cut notch
  • notch deepens by further erosion- overlying material collapses (mass movement)
  • process repeats, cliff retreats
  • rock below low tide level is submerged
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26
Q

What are cliffs and how are they formed

A

steep slopes that are usually unvegetated

  • hydraulic action, abrasion form wave-cut notch
  • notch deepens, overlying rock collapses by mass movement due to gravity
  • exposed face forms a cliff
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27
Q

How do cave, arches, stacks and stumps form

A
  • rocks have joints, faults, bedding planes
  • eroded more rapidly, hydraulic action, abrasion deepens and widens weak point- forming cave
  • if 2 caves on either side of headland join up- single cave is eroded- forming arch
  • top of arch collapses- leaving isolated pillar- stack
  • stack is eroded by sea forming stump
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28
Q

What are the four different processes of sediment transport

A

Traction: Sediment rolls along, pushed by waves and currents

Saltation: Sediment bounces along, either due to the force of water or wind

Suspension: Sediment is carried in water columns

Solution: Dissolved material is carried in the water as a solution

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29
Q

Name 3 factors that affect sediment transportation

A
  • angle of wave attack
  • tides
  • currents
  • longshore drift
30
Q

What is longshore drift

A

movement of sand and shingle along the coast

31
Q

How does longshore drift affect sediment transportation

A
  • swash transports sediment up beach at angle due to prevailing winds
  • backwash transports sediment back down beach 90 degrees to coastline
  • sediment particles come to rest along from starting point- lateral movement
  • particle move in zig-zag fashion along beach with incoming wave
32
Q

What depositional landforms are formed as a result of sediment transport deposition

A
  • Beaches
  • Spits
  • Bars
  • Barrier beaches
  • Tombolo
  • Cuspate Foreland
    -Sand dunes
33
Q

What is a spit

A

-long, narrow feature made of sand and shingle which extends from land into sea

34
Q

When do spits form

A
  • sand/ shingle moved along coast by longshore drift

- builds up when coastline chages direction- forming a spit

35
Q

How are beaches formed

A

-wave refraction creates low-energy environment which leads to deposition

36
Q

What is a recurved spit

A

spit which end is curved landwards- into bay

37
Q

How are beaches formed

A

produced by material deposited by constructive waves

-swash has strength to carry material up beach, backwash transports some material back down beach, leaving it deposited

38
Q

What are barrier beaches

A

when spit extends across a bay to join 2 headlands

-they trap water behind them forming lagoons

39
Q

What are tombolos

A

a beach that has formed between a small island and the mainland

40
Q

When does deposition occur

A

when waves no longer have sufficient energy to transport material

-material becomes too heavy

41
Q

What are cuspate forelands

A

triangular shaped headlands that extends out from the main coastline

42
Q

How does current influence sediment transportation

A

current is the flow of water in a particular direction- can transport sediment in nearshore, offshore zones

43
Q

How do tides influence sediment transportation

A

create tidal currents in nearshore, offshore zones which transport sediemnt

44
Q

Name one reason why depositional landforms are vulnerable to change

A
  • made of unconsolidated material -> during storms -> sediment can be eroded -> transported elsewhere

- dynamic (lose material transported by waves, tides, currents, wind)

45
Q

What can help stabilise depositional landforms

A

vegetation- as a result of plant succession

46
Q

definition of plant succession

A

changing structure of a plant community over time as an area of initially bare sediment is colonised by plants

47
Q

How does vegetation stabilise sediment

A
  • roots of plants bind sediment particles together- harder to erode
  • when submerged- plants growing in sediment provide protective layer- surface of sediment not exposed
  • friction with vegetation slows wind speed- protects sediment from wind erosion
48
Q

What effects the size of the wave

A

-Strength of the wind

duration the wind blows for

water depth

wave fetch

49
Q

What is a sediment cell

A

a linked system of sources, transfers and sinks of sediment along section of coastline

50
Q

What are the three types of coastal vegetation that can protect a coastline from erosion

A
  • Coastal sand dunes
  • Coastal salt marshes, found in many river estuaries
  • Coastal mangrove swamps
51
Q

What are Halophytes

A

Plants that can tolerate salt water, either around their roots, being submerged at high tide or salt spray from sea

52
Q

What are Xerophytes

A

Plants that can tolerate very dry conditions (coastal sand dunes) -where sandy soil retains very little water due to drainage

53
Q

What are salt marshes

A

areas of flat, silty sediments that accumulate around estuaries/ lagoons

54
Q

Why does a recurved end occur to a spit

A

Wave refraction and a second dominant wind force material to move in a different direction

55
Q

What are the three different types of weathering

A

mechanical
chemical
biological

56
Q

Describe two types of Mechanical weathering

A

Freeze Thaw- occurs when water enters crack/ joint in rock

  • water freezes and expands 10% exerting a force within cracks, widening and loosening rocks.
  • broken rocks are used as tools in marine erosion

Salt Crystallisation- salt water evaporates- leaves salt crystals behind- these grow, cause stresses in rock- cause it to break

Wetting and drying- rocks in clay expand when wet, contract as they dry- causes them to crack and break

57
Q

Describe the three different types of Chemical weathering

A

Carbonation- rain water mixed with co2 forms weak carbonic acid, mixes with calcium carbonate (in limestone)- forms calcium bicarbonate
-rock disappears as new minerals dissolve in solution

Hydrolysis- breakdown of minerals to form new clay minerals, due to effect of water and dissolved CO2

Oxidation- addition of oxygen to minerals, produces iron oxides and increases volume contributing to mechanical breakdown

58
Q

Describe the two different types of Biological weathering

A

Plant roots
Trees and plant roots growing in cracks and fissures forcing rocks apart

Rock boring on vegetated cliff tops that can contribute to rockfalls

59
Q

Name the 2 ways deposition can occur

A
  • gravity- when energy of transporting water becomes too low to move sediment- large sediment is deposited, then smaller sediment
  • flocculation- when small particles are so small they remain in water- clump together- large enough to sink
60
Q

What is biological weathering

A

breakdown or rock in situ by living/ once-living organisms

61
Q

What is mass movement

A

downslope movement of material under force of gravity

62
Q

How does the type of mass movement depend upon lithology

A
  • unconsolidated material- leads to slumping

- consolidated rock- sliding

63
Q

Name the 3 distinctive landforms mass movement creates

A
  • rotational scars
  • talus scree slopes
  • terraced cliff profiles
64
Q

What are human changes that can cause beach profiles to change?

A

construction of dams blocking sediment supply

global warming creating more storms
coastal management intefering with sediment supply

65
Q

What is a blowhole

A

co,bination of 2 features;

-pothole on top of cliff -> created by chemical weathering

-cave formed by marine erosion

-as cave erodes deeper, pothole deepens -> meet -> gap is created for waves to enter travel in and up cliff

66
Q

What are the 4 processes of sediment transport, and the type of sediment they transport?

A

traction - pebbles, boulders
saltation - sand sized particles
suspension - silt and clay particles
solution - chemical compounds in solution

67
Q

What is a swash aligned coast?

A

Where wave crests approach parallel to the coast, so -> limited longshore drift

68
Q

What is a drift aligned coast?

A

where wave crests approach at significant angle -> longshore drift causes sediment to travel far up beach

69
Q

Name 2 factors which effect transportation of sediment

A

-swash-aligned - wave crests paralell to coast -> limited LSD

-drift-aligned - wave crests significant angle -> LSD -> sediment far up beach

70
Q

Desposition is a gradual and continous process

-name 2 forms of desposition

A

-gravity settling -> when waves energy = v low -> heavy rocks, boulders deposited

-flocculation -> clay particles clump together due to chemical attraction and then sink -> ^ density

71
Q

How do sand dunes form

A

when prevailing winds blow sediment to back of beach

geography (55 decks)

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