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Geography > Topic 2: Coasts > Flashcards

Topic 2: Coasts Flashcards

1
Q

What is the littoral zone?

A

Area of the coast where the land is subject to wave action.

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2
Q

What are the 4 subzones within the littoral zone?

A

-Backshore
-Foreshore
-Nearshore
-Offshore

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3
Q

What are the 2 main types of coast?

A

-Rocky
-Coastal plains

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4
Q

What are the 2 types of rocky coastline cliff profile?

A
  • Marine erosion dominated
  • Sub aerial process dominated
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5
Q

What are the 2 types of coastal plain?

A
  • A fall in sea level
  • Coastal accretion
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6
Q

What is an emergent coast?

A

Those resulting in a fall in sea level or uplift of land.

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7
Q

What is a submergent coast?

A

Those resulting in a rise in sea level or fall in land surface.

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8
Q

What is a stable or neutral coast?

A

Those showing no signs of changes in sea level or in the land.

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9
Q

What is a compound coast?

A

Those with a mixture of at least 2 of the above.

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10
Q

What is a primary coast?

A

Where the influence of the sea has been minimal, e.g fjords or deltas.

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11
Q

What is a secondary coast?

A

Where marine processes have been dominant e.g stacks and spits.

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12
Q

What is an advancing coast?

A

Where marine depostion of the uplift of land is dominating.

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13
Q

What is a retreating coast?

A

Where marine erosion or submergence of land is dominant.

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14
Q

What is an high energy environment?

A

Exposed coast facing prevailing winds with long wave fetches resulting in powerful waves.

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15
Q

What is a low energy environment?

A

Sheltered coast with limited fetch, and low wind speeds resulting in small waves.

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16
Q

What is a protected environment?

A

Where wave action is limited in small sheltered sea areas.

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17
Q

What is the tidal range of micro, meso and macro tidal coasts?

A

-Microtidal=0-2m
-Mesotidal=2-4m
-Macrotidal=>4m

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18
Q

What is a concordant coastline?

A

Bands of more resistant and less resistant rock run parallel to the sea.

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19
Q

What is a dalmation coastline?

A

Formed as a result of sea level rise, when valleys flooded, the tops of the ridges remained above the surface of the sea as a series of offshore islands which run parallel to the coast e.g. the Dalmation Coast Croatia.

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20
Q

What is a discordant coastline?

A

Where the geology alternates between bands of more more reisstant and less resistant rock which run perpendicular to the sea.

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21
Q

What is a haff coastline?

A

Consists of concordant features - long spits of sand and lagoons alligned parallel to the coast e.g southern shore of the Baltic sea.

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22
Q

How to headlands and bays form?

A

More resistant rock such as chalk and limestone tend to form headlands, whilst weaker rocks such as shale and clays are eroded to form bays e.g peveril point and swanage bay.

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23
Q

What is lithology?

A

The physical characteristics of rocks.

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24
Q

What is coastal morphology?

A

The shape and form of coastal landscapes and their features.

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25
Q

What are bedding planes?

A

Natural breaks in rock strata caused by gaps in time during rock formation.

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26
Q

What are joints?

A

Vertical fractures in the rock caused either by contraction as sediments dry out or by earth movement during uplift.

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27
Q

What are folds?

A

Formed by pressure during tectonic activity mkaing rocks buckle and crumple.

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28
Q

What are faults?

A

Formed when the stress or pressure to which a rock is subjected exceeded it’s internal strength causing it to fracture. The faults then slip or move along fault planes.

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29
Q

What are fissures?

A

Small cracks in rocks, represent weaknesses that erosion can exploit.

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30
Q

What is a dip?

A

Refers to the angle at which rock strata lie.

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31
Q

What factors influence cliff profile?

A
  • The resistance of the rock
  • The dip of rock strata in relation to the coastline.
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32
Q

What is a horizontal dip?

A

Vertical or near vertical cliff profile with notches which reflect strata which is more easily eroded.

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33
Q

What is a seaward dip high angle?

A

A sloping low angle profile with 1 rock layer facing the sea, vulnerable to rock slides down the dip slope.

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34
Q

What is a seaward dip low angle?

A

The profile may exceed 90degrees producing areas of overhanging rock, very vulnerable to rock falls.

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35
Q

What is a landward dip?

A

Steep profile of 70-80 dgrees, producing very stable cliff with reduced rock falls.

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36
Q

What is a rock?

A

An aggregate of minerals.

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37
Q

What does permeable mean?

A

Rocks that allow water to flow through them and include sandstone and limestone.

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38
Q

What does impermeable mean?

A

Rocks that do not allow ground water flow and include clays, and most igneous and metamorphic rocks.

39
Q

What is gneiss?

A

Metamorphic rock

40
Q

What is conglomerate?

A

Sedimentary rock

41
Q

What is gabbro?

A

Igneous rock

42
Q

What causes waves?

A

Waves are caused by friction between wind and water, transferring energy from the wind into the water.

43
Q

What factors do waves depend on?

A
  • The strength of the wind
  • Depth of water
  • How long the wind has been blowing
  • The fetch
44
Q

What is the fetch from Florida to Cornwall?

A

400km

45
Q

Why do waves break at the shoreline?

A

In deep water, waves have a circular orbit, as waves approach the shoreline the trough experiences friction with the seabed. This causes the orbit to become more elliptical. Evenetually the crest outruns the rough and the wave topples over.

46
Q

Characteristics of constructive waves

A
  • Low frequency (around 6-8 waves a minute) and low energy.
  • Low and have a long wave length giving them a more eliptical cross profile.
  • Stronger swash than backwash, sediment is moved up the beach making it wider. water percolates the beach material in the backwash.
47
Q

Characteristics of destructive waves

A
  • High and steep
  • Have a more circular cross profile
  • Short wave length and high frequency (10-14 waves a minute)
  • Stronger backwash than swash
48
Q

How do constructive waves alter the beach morphology and sediment profile?

A
  • Produce berms at the point where swash reaches the high tide line.
  • Swash can carry sediment of all sizes up the beach but backwash only carries smaller particles leading to a sorting of material in the foreshore zone, with larger heavier shingle at the back of the beach.
49
Q

How do destructive waves alter the beach morphology and sediment profile?

A
  • Weak swash and powerful backwash produces a net transport of sediment down the beach reducing beach gradient
  • ## Large sediment dragged down the beach by backwash forms a wide ridge below the low tide mark at the start of the offshore zone.
50
Q

What are marine processes?

A

Those associated with the action of waves for example, erosion, deposition and transportation.

51
Q

What is erosion?

A

Refers to the wearing away of land and removal of materials by river,seawater, ice and wind.

52
Q

What is hydraulic action?

A

When a wave advances, air can be trapped and compressed in cracks. When the wave retreats the pressure is released explosively which can shatter the rock around the joint and crack

53
Q

What is abrasion?

A

When waves advance, they pick up sand and pebbles from the seabed. When they break at the base of the cliff this transported material is hurled at the cliff base chipping away at the rock face.

54
Q

What is attrittion?

A

Boulders, rock particles and pebbles are continually moved around by waves, as they move they collide with with another and are broken down into smaller, rounder pieces.

55
Q

What is solution?

A

Seawater and saltspray from waves may react with rock minerals and actively dissolve them.

56
Q

What does geomorphic mean?

A

Relates to the formation and shaping of landforms and landscapes by natural processes such as weathering, mass movement, transportation and erosion

57
Q

How is a wave cut notch formed?

A

At high tide, destructive waves may reach the base of a cliff. These waves break onto the cliff and abrasion and hydraulci action wear away the rock. A curved wave cut notch forms along the edge of the cliff.

58
Q

How is a wave cut platform formed?

A

As the cliff is eroded at the base the rock above is left unsupported and eventually collapses under the the influence of gravity. This leaves a flat or slightly sloping area of rock between the high and low tide levels.

59
Q

How are cliffs formed?

A

Marine erosion of land between the high and low tide marks forms a wave cut notch. The notch deepens until the overlying rock collapses due to gravity. The exposed face forms a cliff.

60
Q

What is the cave,arch,stack,stump sequence?

A

At a headland, waves will be refracted so that their full energy will be concentrated on the weak points on the sides, Hydraulic action and abrasion erode joints forming a cave, this cave is deepened creating a tunnel through the headland which is an arch. Undercutting of the sides of the arch leads to the collapse of some overlying material by mass movement widening the arch. The roof of the arch is attacked by weathering and subariel processes causing it to collapse leaving a pillar of rock at the seaward end of the headland called a stack. Erosion at the base of the stack will form notches and it will become unstable and collapse forming a stump.

61
Q

How are beaches formed?

A

Beaches are accumulations of sand and shingle in the foreshore and backshore zones. They are produced by material deposited by constructive waves. Berms are ridges of sand and pebble at the high tide mark. Beach cusps are crescent shape indentations created by constructive waves approaching the beach at an angle.

62
Q

How is an offshore bar formed?

A

A ridge of sand or shingle running parallel to the coast on the offshore zone. They form from sediment eroded by destructive waves and carried seawards by backwash. The sediment is deposited at the boundry of the offshore and nearshore zone, Currents also supply the sediment. Recently used as sites for wind farms such as Scroby Sands in Norfolk or to provide sand for beach nourishment.

63
Q

How is a barrier beach formed?

A

Linear ridges of sand or shingle extending across a bay, it traps a body of seawater behind it called a lagoon. Can form on drift alligned coasts when longshore drift extends a spit across the entire width of a bay. Or when rising sea levels cause constructive waves to drive a ridge of sediment onshore to coastlines with a gently sloping shallow sea bed. e.g Chesil Beach Dorset. large Barrier beaches form islands protecting the mainland from storms and the sheltered area behind is a low energy environment.

64
Q

How do spits form?

A

Linear ridges of sand or shingle stretching into the sea beyond a turn in the coastline. At the turn, longshire drift continues in the original direction but its energy is dispersed, lost as the wave refracts and currents spreads leading to depostion. Overtime sufficent sediment is deposited to break the surface. The area behind is sheltered and there are mudflats and salt marshes. As the spit grows, the tides and currents or secodnary wind and wave direction turn the end of the spit into a hook (recurved spit).

65
Q

How do double spits form?

A

When 2 spits extend outwards in opposite directions from both sides of a bay towards the middle. Form when longshore drift is operating in different directions on opposite sides of the bay, e.g poole harbour and durlston head.
Can also form when rising sea levels drives ridges of matieral onshore from the offshore zone.
Or a bar is breached by river currents

66
Q

How is a tombolo formed?

A

Linear ridge of sand and shignle connecting an offshore island to the mainland. Formed by longshore dirft. E.G Portland Bill.

67
Q

How is a cuspate foreland formed?

A

Low lying triangualr shape headlands formed from deposited sediment. Formed when longshore dirft currents from opposing directions converge at the boundry of 2 sediment cells. The 2 spits shelter the area behind. Further depostion in the slack water and alluvial deposits from small streams caused the area to fill with sediments, mudflats and salt marshes form. E.G Dungeness in Kent is the largest cuspate foreland in europe.

68
Q

What is a sediement cell?

A

A linked system of sources, transfers and sinks of sediment along a section of coastline, acts as a closed system.

69
Q

How many sediment cells are in England and Wales?

A

11

70
Q

What are some examples of sources in the sediment cell concept?

A
  • Cliff erosion
  • Onshore currents supplying sediments to the shore.
  • Land sediment eroded by rivers
  • Wind blown (aeolion) sediment from land
  • Subariel processes (weathering and mass movement)
  • Shells and remains of marine organisms.
71
Q

What are some examples of transfers in the sediment cell concept?

A
  • Longshore drift
  • Wave transport through swash and backwash
  • Tides moving sediments in and out
  • Localised currents or large scale currents
  • Wind (alongshore, offshore or onshore)
72
Q

What are some examples of sinks in the sediment cell concept?

A
  • Backshore depostional landforms (sand dunes)
  • Foreshore depostional landforms (Beaches)
  • Nearshore depositional landforms ( Bars)
  • Offshore depostional landforms (Barrier islands)
73
Q

Why is the coastal system in dynamic equilibrium?

A

Inputs of sediment from the source region are balanced by the amount being deposited in sinks. Its dynamic as although it’s in balance theres a constant movement of sediment in the system.

74
Q

What is negative feedback?

A

Maintains a balance within the system, e.g wave erosion caused rock falls which protects the base of the cliff from further erosion.

75
Q

What is positive feedback?

A

Changes the balance until a new equilibrium is reached. e.g sand dunes are damaged during a storm which created a blowout allowing wind to move sand away preventing marram grass from regrowing leading to more erosion.

76
Q

What are subariel processes?

A

Combination of mass movement and weathering that alter the shape of the coastline.

77
Q

What is weathering?

A

The breakdown of rocks in situ at or near the surface of the earth exploiting weaknesses in rocks over a long time scale.

78
Q

What is frost shattering/freeze thaw weathering?

A

Type of mechanical weathering. Water seeps into cracks in the rocks. When the water freezes it expands in volume by 9% exerting pressure and forcing the rock apart , this process repeats forming angular rock fragments and a jagged cliff face and scree slopes.

79
Q

What is salt crystalliation?

A

A type of mechanical weathering. When salt water seeps into cracks in rocks The water evaporates leaving behind salt crystals in cracks, These salt crystals expand as they are heated exerting pressure on the surrounding rock forcing it apart. Over time this will weather the coastal landscape leaving scree slopes.

80
Q

What is oxidation?

A

A type of chemical weathering. Oxygen combines with iron based minerals in rock causing a chemical breakdown of the materials shown by a rusty colour on the rock face. The rock minerals will no longer be bonded together so parts of the rock will crumble making erosion easier.

81
Q

What is hydrolysis?

A

A type of chemical weathering. Occurs when water reacts with minerals in the rock causing the chemical composition of the rock to change and become more unstable.This makes the rock more susceptible to decompostion.

82
Q

What is carbonation?

A

A type of chemical weathering. Occurs when carbonate dioxide from moisture in the air reacts with carbonate minerals in rock creating carbonic acid which breaks down rock.

83
Q

What is plant root weathering?

A

A type of biological weathering. A seed from a plant lands in a crack in a rock, as the plant grows it’s roots expand and thicken. and exert force on the rock causing the crack to widen. Eventually angular frgaments of rock break away.

84
Q

What is rock boring?

A

A type of biological weathering. Many marine molluscs live on coastal rocks scapring away at the rock surface to get food or make a home, e.g Piddocks. Pebbles and rocks with hole bored into them are easily moved around by waves, they also provide weaknesses for other weathering processes to act upon.

85
Q

What is seaweed acids?

A

A type of biological weathering. Some seaweed like kelp contains pockets of sulphuric acid so when these cells break break in contact with rock the acid will dissolve some minerals.The rock minerals will no longer be bonded so parts of a rock will crumble and these become points of greater erosion.

86
Q

What is mass movement?

A

The movment of material downslope as a result of gravity. Caused by gravity once a slope has become unstable. After waves have undercut resistant rock or when rain enters unconsolidated rock and forces particles apart so they no longer cohere.

87
Q

What are rock falls and talus slopes?

A

Rock falls occur on steep slopes as a cliff face is weathered which loosens rock. Can occur by weathering or marine erosion. Rock fragments fall to the base of the cliff and form talus scree slopes which is when rock falls almost vertically down the cliff face.

88
Q

What is topple?

A

Topples are the movement of rock debris or earth masses by forward rotation. Often results in the formation of debris or a debris cone at the base of the slope called a talus cone.

89
Q

What is rotational slumping/sliding?

A

Rotational slumping involves rock failure and movement along a curved rock plane. It occurs in weak rocks and unconsolidated sediment. Water adds weight and acts as a lubricant.

90
Q

What is soil creep?

A

Slow downhill movement of soil and debris under influence of gravity. Can cause gradaul tilting of fences and trees common on slopes with a gentle gradient.

91
Q

What are mudflows?

A

Fast moving mass of water saturated soil, rock and debris moving downhill due to gravity. Water acts a lubricant. Common in areas of loose unconsolodated soil.

92
Q

What is solifluction?

A

Downslope flow of waterlogged soil in tundra regions. Upper layer of soil thaws while the underlyimng permaforst remains frozen so the saturated surface layer becomes heavy and gradully moves downhill forming tercettes.

93
Q
A

Geography (4 decks)

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