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temp > Coastal Landscapes and Change EQ1 > Flashcards

Coastal Landscapes and Change EQ1 Flashcards

1
Q

What is the littoral zone?

A

The area of shoreline where land is subject to wave action. It’s subdivided into offshore, nearshore, foreshore and backshore.

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2
Q

What is the offshore?

A

The area of deeper water beyond the point at which waves begin to break. Friction between waves and the sea bed may cause some distortion of the wave shape.

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3
Q

What is the nearshore?

A

The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the waves sufficiently and causes it to break (breaker zone).

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4
Q

What is the foreshore?

A

The area between the high tide and low tide water marks.

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5
Q

What is the backshore?

A

The area above the high tide mark, affected by wave action only during major storm events.

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6
Q

What are the different types of coastal landscapes formed by the littoral zone?

A
  • Rocky (cliffed coastline)
  • Sandy coastline
  • Estuarine coastline
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7
Q

What is the characteristics of a rocky coastline and where does it form?

A

Rocky coastlines usually form in areas with reistant geology, in a high energy environment were erosion is greater then deposition.
It creates areas of high relief varying from a few metres to hundred of meters
E.g. chalked cliffs at Flamborough Head Yorkshire

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8
Q

Where do Sandy coastlines form, and what are their characteristics?

A

Sandy coastlines form in areas of low resistant geology, low energy environments (constructive waves) were deposition is greater than erosion.
They are areas of low relief with sand dunes and beaches that are flatter.

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9
Q

Where do Estuarine coastlines form, and what are their characteristics?

A

They form in river mouths, low energy environments, less resistant rock where deposition is greater than erosion.
They are areas of low relief wiht salt marshes and mudflats.

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10
Q

Why is the littoral zone a dynamic zone of rapid change?

A

It can be described as a dynamic zone as
Short term > there are constantly changing inputs, through flows and outputs of energy and material. (Weather and high and low tide variations due to lunar month)
Long term > sea level variations due to climate change

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11
Q

How can coast be classified using long term criteria?

A
  • geology (Rocky, Sandy or estuarine)
  • changes in sea level (emergent or submergent)
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12
Q

How can geology help to classify coastlines?

A

Geology is all the characteristics of land such as lithology (rock type) and structure. It can be used to classify coastlines as
- rocky, sandy or estuarine
- concordant or discordant

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13
Q

How can sea level rise be used to classify coastlines.

A

Sea level change can be used to classify coasts as
- emergent or submergent

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14
Q

What are the short term criteria that can be used to classify a coastline?

A
  • input from rivers
  • inputs from waves
  • inputs from tides
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15
Q

How can energy input be used to classify coastlines.

A

Coasts receive energy inputs mainly form waves but also from currents, rivers and gravity. It can be used to classify a coast as
- high energy or low energy

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16
Q

What is a high energy coastline?

A
  • exposed coasts
  • facing prevailing winds
  • long wave fetches
  • powerful destructive waves
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17
Q

What is a low energy coastline?

A
  • sheltered coasts
  • limited fetch
  • low wind speeds
  • small constructive waves
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18
Q

How can inputs from tides be used to classify a coastline?

A

Tidal range varies hugely in coastlines meaning coasts can be classified as
- Microtidal (tidal range between 0-2 metres)
- mesotidal (tidal range of 2-4 metres)
- macrotidal (tidal range greater than 4 m)

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19
Q

What are rocky coastlines?

A

Rocky coastlines are coastlines where solid rock is dominant. They occupy 1,000 km of the UKs coastline. Cliffs can vary in height from high relief areas to low relief areas.

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20
Q

Where do Rocky coastlines normally form?

A

Rocky coastlines from in areas of
- resistant geology(their lithology and structure means they erode and weather slowly)
- high energy environments (erosion is greater then deposition)

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21
Q

What are coastal plain landscapes?

A

Coastal plain landscapes include both Sandy and Estuarine coastlines. Their littoral zones consists of sand dunes, beaches, mudflats and salt marshes.

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22
Q

What are the characteristics of a coastal plain?

A
  • relatively flat, low relief areas adjacent to the sea
  • often contain freshwater wetlands and marshes due to the poor drainage of the flat landscape
  • littoral zones in composed of sand dunes, mudflats and salt marshes.
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23
Q

Where do coastal plain landscapes form?

A
  • low energy environments (deposition is greater than erosion) net accumulation of sediment
  • low relief
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24
Q

How do coastal plains form?

A

They forms through the coastal accretion (continuous net deposition of sediment) from
- offshore sources (transported by waves, tides or current)
- terrestrial sources (rivers, glaciers, wind or mass movement)
They can also be formed through sea level change (falling sea level)

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25
Q

Why are coastal plains described and a dynamic equilibrium?

A

As there is a balance in the forces of
- deposition of sediment from river systems inland and deposition of sediment from offshore and longshore sources
- erosion by marine action at the coast

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26
Q

What two coastlines do geological structure form?

A
  • concordant
  • discordant
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27
Q

What is a concordant coastline?

A

When rock starts run parallel to the coast.

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28
Q

What are discordant coastlines?

A

When different rock strata intersects the coasts at an angle so geology varies along the coastline.

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29
Q

What does geological structure include?

A

It refers to the arrangement of rocks in 3D. It includes
- strata (differnt layers of rock within an area and how they relate to each other)
- deformation (degree of rock units that have been deformed by tectonic activity)
- faulting (major fractures)

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30
Q

What is morphology?

A

The shape of the landscape features. It is influenced by geological structure (headlands and bays, Dalmatian and Haff).

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31
Q

What landforms are formed along a concordant coastline?

A
  • Dalmatian coastline
  • Coves
  • Haff coastlines
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32
Q

How does coves form?

A

At a concordance coastline with hard rock (limestone) forming a protective layer parallel to the sea, with a soft rock behind (clay).
1. The hard rock erodes very slowly retreating inland though undercutting
2. At points were the hard rock is weakened (faults/fractures) erosion can break through exposing the soft rock to rapid erosion.
3. This creates a serie of coves
E.g. Lulworth Cove on the Souht Dorset Coast (Portland limestone is the hard rock and Wealden clay the soft).

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33
Q

How do Dalmatian coast form? and example

A

At a concordant coastline, past tectonic forces has created folded ridges anticlines and down folded valleys synclines aligned parallel to the coast. Sea level rise has flooded the synclines producing lines of narrow island.
E.g. In Croatia on the Adriatic Sea (tectonic forces were the collision of the African and Eurasian plates)

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34
Q

How do Haff coastlines form?

A

On a concordant coastline Haff coasts forms through
1. Deposition produces up consolidated geological structures topped with sand dunes run parallel to the coastline just offshore
2. The sand ridges formed bars across some bays and river mouths, creating a lagoon behind filled with trapped water.
E.g. On the Southern fringes of the Baltic Sea

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35
Q

What geological structures are created at disconcordant coastlines?

A

Headlands and bays

36
Q

How are headlands and bay created?

A

At a disconcordant coastline
1. Along the coastline differential erosion takes place eroding the less residant rock at a much faster rate than the more resistant rock
2. The eroded soft rock form bays with the harder rock protruding outwards as a headland
The relative resistance and vulnerability of the rock to erosion determines the degree of indentation of bays.
E.g. West Cork Ireland

37
Q

Why do headlands and bays ‘smooth out’ over time?

A
  • in deep water wave crests are parallel
  • as the waves approach the shallower water offshore of a headland, friction causes them to slow down increasing wave height.
  • the causes the wave to refract becoming curved (convex in bays dispersing the energy and concave at headlands concentrating the energy)
  • this increases the rate of lateral erosion in the headland.
38
Q

What geological structures influence coastal morphology?

A
  • jointing
  • dips
  • faulting
  • folding
39
Q

What are joints?

A

Joints are fractures in the rock created without displacement. They occur in most rocks often in regular pattern dividing the strata up into block with regular shape.

40
Q

How are joints formed?

A
  • in igneous rocks as magma contracts as it looses heat, cooling joints form.
  • in sedimentary rock, joints form whne rock is subjected to compression or stretching by tectonic focus.
41
Q

How do joints affect erosion rates?

A

Joints increase erosion rates by creating fissures which marine erosion processes such as hydraulic action can exploit.
E.g. Stair Hole cove the Purbech limestone is intensely folded creating heavy joints increasing rates of erosion

42
Q

What are faults?

A

Faults are major fracture in rocks created by tectonic forces, with displacement of rocks either side of the fault line. They are often very large scale extending many of kilometres.

43
Q

How do faults increase the rate of erosion?

A

They significantly increase the rate of erosion as huge forces are involved with faulting creating heavily fractured and broken rocks either side of the fault which are easily exploited by marine erosion.
E.g. Bantry Bay in Cork Ireland a major fault runs down the centre of the bay resulting in rapid erosions

44
Q

What are folds?

A

Folds are bends in the rock. They are produced by sedimentary rock layers being squeezed by tectonic activity. The main types are anticlines and synclines

45
Q

What impact do folds have on the rate of erosion?

A
  • they are often more heavily fissured and jointed making them more vulnerable to erosion
  • also increases angle of dip
46
Q

What is a fissure?

A

Very small cracks in the rock.

47
Q

What is a dip?

A

The angle of inclination of the rock strata from the horizontal. They from whne tectonic forces tilt or fold the horizontal sedimentary rock.

48
Q

What are the different types of dip?

A
  • horizontal dip
  • high angle seaward dip
  • low angle seaward dip
  • landward dip
49
Q

What is a horizontal dip?

A

Produces a vertical cliff angle. It contains many notches due to weathering making it more easily eroded and resulting in small scale mass movements

50
Q

What is a high angle seaward dip?

A

Produces a sloping, low angled profile with the outer rock layer facing the sea. They are vulnerable to sub aerial processes, meaning the mass movements here are rock slides.

51
Q

What is a low angle seaward dip?

A

Produces a steep profile that may exceed 90 degrees, creating areas of overhanging rock. This makes them very vulnerable to mass movement of rock falls. Major rock falls happen when undercutting by marine erosion makes the overhang unsustainable.

52
Q

What is a landward dipping strata?

A

A steep profile with a slight downslope. Gravitational forces pull loosens blocks into place making the cliff very stable with only a few rock falls.

53
Q

What is a cliff profile?

A

The height and angle of a cliff face. As well as its features (wave cut notches)

54
Q

What are microfeatures?

A

Small scale coastal features such as caves and wave cut notches which forms part of cliff profiles.

55
Q

Where do micro features form?

A

They form is areas weakened by heavy jointing creating faster rates of erosion.

56
Q

How does geological structure influence the development of coasts landscapes?

A

Geological structure is responsible for
- the formation of concordant and disconcordant coasts
- coastal morphology (Dalmatian, Haff, headlands and bays)
- Erosion rates (fault joint ect)
- occruance of micro features

57
Q

What influences rates of coasts recession and stability?

A
  • bedrock lithology (type of rock)
  • differential erosion of alternating strata (permeable/impermeable, resistant/less resistant)
  • amount and type of vegetation
58
Q

What is lithology?

A

Litholgy is the type of rock.
It includes mineral composition, rock class, structure (fissures and cracks), dip)

59
Q

How does litholgy affect erosional resistance?

A
  1. Mineral composition - some rock contain reactive mineral (calcite in limestone) that are easily broken down by chemical weathering
  2. Rock class - sedimentary rock with weak cementation compared to igneous and metamorphic rocks are crystalline with strong chemical bonds
  3. Structure - rocks wiht fissured and joints or air space (porous) weather and erode more rapidly
  4. Dip of rock strata
60
Q

What are igneous rock (how is it formed)?

A

Igneous rocks are formed from solidified lava or magma. Examples include granite, basalt and pumice. Has a very slow rate of erosion.

61
Q

Why does igneous rock have very slow rates of erosion?

A

Igneous rocks have a very slow rate of erosion as
- they are crystalline wiht the interlocking crystals make a strong, resistant rock
- often have few faults limiting amount if weaknesses that erosion can exploit

C > newly formed lava and solidified ash erode easily and newly formed volcanic islands can exhibit very rapid erosion rates

62
Q

How does metamorphic rock form?

A

Metamorphic rock is formed by the recrystallisation of sedimentary and igneous rock through heat and pressure. Examples include slate and marble. They have slow rate of erosion.

63
Q

Why does metamorphic rock have a slow rate of recession?

A

It is hard and resistant as
- it has a crystalline structure
Less resistant than igneous as
- their crystals are often orientated in the same direction making them weaker than interlocking crystals of igneous rock
- often heavily folded and fractured

64
Q

How is sedimentary rock formed?

A

Sedimentary rock is formed by the compaction of deposited organic material under heat and pressure. Examples include sandstone, limestone and shale. They have moderate to fast rates of erosion.

65
Q

Why does sedimentary rock have moderate to fast rates of erosion?

A
  • most sedimentary rocks are clastic (composed of broke pieces of older rocks)
  • often heavily jolted as a result of compression and pressure
  • older sedimentary rocks tend to be stronger (as it is buried deeper and is subject to joe intense compaction)
66
Q

What is unconsolidated sediment?

A

Sediment that is not yet been cemented to form solid rock (lithification). This means it’s looses and easily eroded. Examples include boulder clay

67
Q

How does cliff composed of differing litholgy create a complex cliff profile?

A

A complex cliff profiles are created when the cliffs are composed of strata with differing litholgy.
- less resistant strata erodes and weathers faster whereas as resistant strata will retreat less rapidly.
- creating bench features or overhanging sections

68
Q

What forms a complex cliff profile (How does lithology vary)?

A

Differential erosion of alternating starta in cliffs
- permeable vs impermeable rock strata
- resistant vs less resistant rock strata
Produce complex cliff profiles

69
Q

How does rock permeability create a complex cliff profile and affect erosion rates?

A
  • permeable rocks tend to be less resistant to weathering as water percolates through increasing the surface if the rock that can be chemical weathered (limestone weathered by carbonation converting calcium carbonate to soluble calcium bicarbonate). Also stability affected by pore water pressure
  • impermeable rocks do not allow water to flow through them (mist igneous and metamorphic rocks are impermeable as well as clay)
70
Q

What is pore water pressure?

A

The pressure water experiences at a particular point below the water table due to the weight of the water above it.

71
Q

How does rock permeability affect pore water pressure causing increased rates of erosion?

A
  1. Groundwater flow through rock layers can create high pore water pressure within cliffs when is is unable to percolate down into the lower layers
  2. Water accumulates in permeable layer filling all the pores in the rock with water
  3. A spring will form at the top of the saturated layer
  4. The stream will flow down the cliff eroding the cliff face reducing angle of cliff profile.
72
Q

Why do permeable rock eroded at a faster rate?

A
  • A spring creating erosion
  • Groundwater flow removing the cement binding sediment together
  • Pore water pressure leads to slumping and sliding
  • Saturation leads to slumping and sliding (mudslides)
  • Higher SA for chemical weathering
73
Q

2B.3 C

A

Vegetation in stabilisation

74
Q

How does vegetation stabilise Sandy coastlines?

A

Coastline are protected from of unconsolidated material
- plant roots bind sediment together, making it harder to erode
- when submerged plants growing in sediment provide a protective layer so the surface of the sediment is not directly exposed to moving water and therefor erosion
- plant protect sediment from wind erosion by reducing wind speed at the surface due to friction with the vegetation.

75
Q

How does vegation increase rates of deposition?

A
  • plant stems and leaves irruption the flow of wind and water reducing velocity and encouraging deposition
  • when vegetation dies is adds organic matter (humus) to the soil.
76
Q

Why does the coast provide an extreme environment for vegetation growth?

A
  • exposure to high winds speeds
  • submerged in salty water
  • evaporated sea spray make the sediment salty
  • salt is highly porous and absorbs rainwater meaning plants have little fresh water
  • sand lacks nutrients
77
Q

What is the definition of halophytes?

A

Halophytes are plants that are specially adapted and can tolerate salt water or salty conditions.

78
Q

What is the definition of xerophytes?

A

Pants that are adapted to tolerate very dry conditions. (Sandy retains very little water)

79
Q

What are pioneer species and how do they modify the environment?

A

These are the first plants to colosnise freshly deposited sediment. They modify the environment by
- stabilising sediment
- adding organic matter beginning the process of soil formation
- reduce wind speeds at sand surface allowing more sediment to be deposited.
This means less developed species can colonise

80
Q

What is the definition of plant succession?

A

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

81
Q

What is a sand dune succession called?

A

A psammosere

82
Q

What is the process of psammosere succession?

A
  1. Embryo dunes form when a object (seaweed, drift wood) provinces a barrier trapping sand.
  2. As the embryo dunes grows in size it is colonised by xerophyic pioneer plants (marram grass). They alter the conditions allowing other plants to colonise forming foredunes
  3. As new species colonise the sediment is further stabilised resulting in yellow dunes
  4. When the vegetation dies it adds organic matter to the sand as humus, creating soil
  5. The conditions are now very much improved wiht soil provide moisture retention and nutrients this allows non specialised plants to colonise until a climax community is reached.
83
Q

What is a salt marsh succession called?

A

Halosere

84
Q

What is a halosere?

A

A plant succession that takes place on bare mud deposited in estuaries at the mouth of rivers, which is exposed at low tide but submerged at high tide.

85
Q

Why are estuarine areas ideal for salt marshes?

A
  • they are sheltered from strong strong waves meaning they’re is high rate of mud and silt depositions
  • rivers transport a supply of sediment to the river mouth
86
Q

What is the process of halosere succession?

A
  1. Mixing of fresh water and sea water in the estuary causes clay particles to be deposited through flocculation
  2. Blue-green algae and gut weed colonise the exposed mud
  3. The algae binds the mud together and adds organic matter and traps sediment
  4. As the sediment thickens water depth is reduced and the mud is submerged for less time
  5. Halophyic plants colonise the area
  6. An accumulation of organic matter and sediment raises the height of the marsh until it’s only covered by spring tides
  7. The higher marsh is then colonised by less adapted plants
  8. Rainwater washes salt out of the high marsh soil allowing land plants to colonise
  9. A climax community is reached
87
Q

What is a halosere?

A

A plant succession that takes place on bare mud deposited in estuaries at the mouth of rivers, which is exposed at low tide but submerged at high tide.

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