3.3-Coastal Landscape Development

Question 1

Globally, individual coastal locations will have a coastal landscape with features that reflect the interaction of a range of factors (amongst other things):

Answer 1

• coastal geology and lithology
• climate
• nature of tides and waves

Question 2

Despite the sheer variety of coastlines, it is possible to place coastlines in a simple classification in which they can either be:

Answer 2

• concordant or discordant
• a cliffed coast or flat coast
• emergent or submergent coastline

Question 3

When studying the formation of different landforms it is important to be able to see the formation of each landform as a system with inputs, processes and outputs:

Answer 3

Inputs:

• coastal geology
• climate
• nature of waves

Processes:

• erosion
• weathering
• deposition
• wave refraction
• sea level change

Outputs:

• sediment
• landforms

Question 4

Describe brief overview of headlands and bays (spec doesn’t require to describe but important in the formation of other landforms)

Answer 4

• Areas with alternating more and less resistant rocks are a common feature of many coastlines (discordant coastlines)
• initially, erosional processes predominate in areas with less resistant rock e.g. clay forming bays, leaving the more resistant rock e.g. sandstone protruding out to sea as headlands
• because of wave refraction the headlands then receive the highest-energy waves and are more vulnerable to forces of erosion than the bay. The bays are subject to deposition due to low-energy waves that allow sediment to accumulate and form beaches; these then act to protect part of the coastline

Question 5

What’s a U.K. Example of headland and bays?

Answer 5

Along the coastline of the Isle of Purbeck in Dorset, there are both discordant and concordant coastlines

Question 6

What are the landforms of erosion we need to know?

Answer 6

• headlands and bays
• cliffs and wave-cut platforms
• cliff profile features: caves, arches and stacks

Question 7

What are the landforms of deposition we need to know?

Answer 7

• beaches
• simple and compound spits
• tombolos
• barrier beaches and islands
• offshore bars
• sand dunes

Question 8

What are the estuarine landforms we need to know?

Answer 8

Mudflats and saltmarshes

Question 9

How are cliffs and wave cut-platforms formed?

Answer 9

1- destructive waves break at the foot of a cliff- energy is concentrated here

2- erosional processes concentrated at the base of the cliff(especially hydraulic action) start to undercut the cliff forming a wave-cut notch

3- the overhanging cliff is subject to weathering and eventually collapses

4- the wave-cut platform is left as a smooth, flat < 5 degrees slope at the base of the cliff between high and low water mark and may be smoothed by further abrasion

5- this process is repeated but as the wave-cut platform grows the waves break further out at sea and their energy is dissipated before reaching the cliffs, reducing rates of erosion on the cliff and slowing down the rate of the growth of the platform. Therefore, wave-cut platforms don’t grow bigger than around 500m (good example of negative feedback)

Question 10

What are the inputs, processes and outputs of the formation of cliffs and wave-cut platforms?

Answer 10

• inputs: wave energy, coastline characteristics
• processes: erosion, weathering and mass movement
• outputs: rock debris and sediment and cliff wave-cut platform

Question 11

What at factors which affect the development of wave-cut platforms?

Answer 11

• rock type
• wave energy
• coastal morphology- faults, strata, folding etc

Question 12

What’s a U.K. example of a wave-cut platform?

Answer 12

Flamborough Head, North Yorkshire, UK

Question 13

What’s a non U.K. example of a wave-cut platform?

Answer 13

Muckross Head, Donegal, Ireland

Question 14

What is a wave-cut platform?

Answer 14

A gently sloping (less than 5 degrees) relatively smooth marine platform caused by abrasion, at the base of a cliff

Question 15

Caves, arches and stacks and their associated features are all described as cliff profile features- they tend to form

Answer 15

On headlands where, due to wave refraction, wave energy is focussed.

Question 16

Explain the formation of caves, arches and stacks

Answer 16

1- where there is a weakness in the rock due to a crack, fault or joint, it is exploited by hydraulic action and is enlarged and either for,s a narrow, steep sided inlet called a geo or where the cliff becomes undercut, a cave forms

2- where caves face the oncoming waves the full force of the waves is applied to the rear of the cave, this can enlarge joints in the cave roof and if the overlying rocks are sufficiently weakened they make collapse forming a blowhole

3- often caves form in headlands as erosion is strongest here. Where caves are eroded on either side of a headland they may erode right through the headland and form an arch. The roof of the arch is weakened through sub-aerial processes and chemical weathering from the sea-spray splashing below, eventually collapsing the roof, leaving a stack

4- the stack’s base is in the intertidal zone so its subject to erosion. The upper part of the stack also becomes weakened and over time the whole stack collapses, usually in stages. This leaves behind a stump which will eventually be eroded to the level of the wave-cut platform

5- the speed which this process takes place depends on the nature of the waves and the rock but it could be anywhere between hundreds to tens of thousands of years for the entire process

Question 17

What are the inputs, processes and outputs of caves, arches and stack formation?

Answer 17

• inputs: wave energy
• processes: erosion, sub-aerial processes e.g. weathering
• outputs: rock debris+sediment and caves, arch, stack/stump

Question 18

What are the factors that affect the development of caves, arches and stacks?

Answer 18

• nature of waves e.g. constructive or destructive

- rock type

Question 19

What’s a U.K. example of cave, arches and stacks?

Answer 19

Old Harry’s rocks, are 3 chalk formations including a stack and a stump in Dorset, Isle of Purbeck, southern England

Question 20

What’s a non U.K. example of caves, arches and stacks?

Answer 20

Twelve Apostles are a series of limestone stacks (associated with caves and arches) off the shore of the Port Campbell National Park in Victoria, Australia

• their proximity to each other has made it popular tourist attraction

Question 21

Where do landforms of deposition occur?

Answer 21

On coastlines where sand and shingle accumulate faster than they are removed- it often takes place where the waves are low energy or where rapid coastal erosion takes place and provides an abundant supply of material

Question 22

Landforms of deposition have to be seen within the context of

Answer 22

Their sediment cell- the form and characteristics of depositional features is controlled by the inputs and outputs. Although a sediment cell is viewed as a closed system, because it functions as one most of the time. However, in general where a depositional feature forms somewhere in a sediment cell it means that elsewhere in the cell is being eroded

Question 23

Deposition generally takes place in areas where

Answer 23

there is a large supply of sediment

Question 24

What are beaches?

Answer 24

Accumulations of sediment and represent important temporary stores within a sediment cell

Question 25

Beaches form between

Answer 25

They are largely formed of either sand or shingle and are formed of material from from offshore sand bars, LSD, wind-blown sand from up the coast and mass movement from the cliffs behind the beach

Question 26

Why do sand beaches tend to be gentle in slope? (<5 degrees)

Answer 26

The sand grains are small and easily compacted which means that little water percolates through the sand and so the majority of water moving up the beach also returns through backwash which smooths and flattens the beach

Question 27

Why do shingle beaches tend to be steeper? (10-20 degrees)

Answer 27

The larger sediment size means that it is less easily compacted and therefore the waves, having broken, percolate back through the shingle meaning that the backwash doesn’t really transport material back down the beach= creates a beach unlikely to be eroded

Question 28

Describe the ‘structure’ of a beach

Answer 28

• Many beaches are a combination of shingle and sand and the larger sediment tends to be at the top of the beach because it takes high energy storm waves to deposit this material
• at the top of the beach a wider flatter area of sediment is deposited by a strong swash during spring high tides = storm berm
• below this there are a series of other ridges or berms which mark a series of high tide lines and are built by constructive waves
• cusps form where the waves break directly directly onto the beach where both swash and backswash are strong and generally form at the junction where the sand on the on the lower part of the beach meets the shingle on the upper part of the beach.
• further down the beach from the cusps, ripples may form in the sand
• at the LWM ridges form where backwash deposits sediment

Question 29

The angle at which waves generally approach a coastline will determine the nature of

Answer 29

the kinds of beach features that develop. The terms swash-aligned and drift-aligned beaches are broad classifications of beach types to reflect the nature of equilibrium between erosion and deposition a beach tends towards

Question 30

What are the characteristics of swash-aligned beaches?

Answer 30

• are generally orientated parallel to the incoming wave crests
• experience minimal LSD

Question 31

What are the characteristics of drift-aligned beaches?

Answer 31

• are generally orientated parallel to the direction of LSD

- can have considerable amounts of sediment transported long distances along them

Question 32

The idea of equilibrium is especially significant for what kind of beach?

Answer 32

Drift-aligned as without a continual supply of sediment the LSD would remove the sediment faster than it was deposited

Question 33

Draw a diagram of a beach and its features

Answer 33

Look to camera roll

Question 34

What’s a UK example of a beach?

Answer 34

Watergate Bay, Newquay

Question 35

What’s a non-UK example of a beach?

Answer 35

Bondi beach, Australia

Question 36

What are spits?

Answer 36

Long, narrow ridges of deposited sediment which are joined to the mainland at one end and stick out into the sea or across and estuary or bay, usually on a drift-aligned coast- they can either be simple or compound

Question 37

What’s the main difference between a simple and a compound spit?

Answer 37

Simple spits are either straight or recurved but do not have minor spits. Whereas, compound spits have a series of minor spits or along their landward side

Question 38

What’s a UK example of a simple spit and compound spit?

Answer 38

• simple spit = Spurn Head, Humberside

- compound spit= Hearst castle spit, Hampshire

Question 39

Explain the formation of spits?

Answer 39

• spits form where material is moved along the coast through LSD but where the coastline changes direction (often due to estuary or river mouth).
• sediment starts to accumulate in the sheltered water in the lee of the headland which begins to form a spit
• during storms larger material is deposited above the HWM which makes the spit more permanent
• the end of the spit may become recurved as wave refraction and secondary winds and waves carry and deposits sediment round the end of the spit- if it recurves enough, this is another change in coastline direction so the spit may continue to grow in the original direction, and this may happen a number of times creating a compound spit
• very fine sediment may be deposited by the river in the ‘slack’ low energy zone behind the spit forming a salt-marsh

Question 40

Why are salt marshes formed from spits important?

Answer 40

Salt marshes are important coastal habitats which may then be further stabilised by the growth of salt-tolerant plants

Question 41

What are factors that affect the development of spits?

Answer 41

• wave refraction
• storms (HWM)
• rate of LSD
• strength of prevailing wind
• anthropogenic Intervention e.g. spit secure

Question 42

A tombolo is where

Answer 42

A spit connects to an island to the mainland. The formation of the tombolo creates more sheltered conditions on the lee-side of it which may lead to deposition and salt marsh formation

Question 43

What’s a U.K. Example of a tombolo?

Answer 43

St Ninian’s, Shetland, British Isles

Question 44

What’s a non-UK example of a spit?

Answer 44

Farewell spit at the northern end of the Golden Bay, New Zealand

Question 45

Where do barrier beaches form?

Answer 45

Where a spit extends across a bay or joins two headlands together- however most of these are thought to have been originally formed when gravel deposited in the English channel when glaciers melted after the last Ice Age was deposited on the coast by constructive waves, forming the barrier beach; LSD has since added more material to these= landforms can be the product of a number of processes over a range of timescales

Question 46

Barrier beaches can only form where

Answer 46

There is no current flowing off the land

Question 47

What forms behind barrier beaches?

Answer 47

Lagoon forms which is usually shallow and marshy and in tropical locations mangrove swamps can form. Over time the lagoons may become full of silt and eventually dry up

Question 48

What’s a UK example of a barrier beach?

Answer 48

Slapton Ley, barrier beach in Devon

Question 49

Where do barrier islands form?

Answer 49

Where barrier beaches become separated from the mainland; they’re usually made of sand or shingle and can be up to 100 miles long and narrow-they become vegetated as they become older an vegetation succession occurs

Question 50

What is not entirely understood about barrier islands?

Answer 50

Their formation-but it is thought that they are formed of sediment deposited when glaciers melted 18,000 years ago at the end of the last Ice Age. It’s probably that currents deposited this material in barrier beaches and that the melting ice also meant that sea levels rose leaving these beaches separated from the mainland

Question 51

Where are barrier island usually found?

Answer 51

In areas with low tidal ranges and gently sloping offshore coastlines. In some cases, very long barrier islands become split into a series of shorter islands as inlets develop between them to allow tides to rise and fall around the island

Question 52

What’s a non-UK example of barrier island?

Answer 52

The West Frisian Islands in the Netherlands

Question 53

How are offshore bars formed?

Answer 53

From sediment deposited by coastal currents including LSD but they remain submerged or semi-submerged offshore beyond the breaker zone. They are formed where currents deposit sand off-shore

Question 54

Discuss the background of sand dunes

Answer 54

• along the UK coastline for most of the day, local differences in air pressure result in wind blowing onshore (wind blows from high pressure over the sea (sea is cooler than land) to the lower area pressure over the land (land is warmer than the sea)
• this onshore wind means that sand is transported up the beach through saltation
• areas which have a large tidal range have large expanses of sand which are exposed and can dry out at low tide and therefore more likely to have sand dunes forming
• offshore sand bars also provide a source of sand

Question 55

What are the stages in sand dune formation?

Answer 55

1- sand is initially trapped by obstacles- this is often on the storm berm where driftwood is deposited
2- as sand is trapped the obstacle grows slowing the wind and therefore contributing to further deposition
3- these first dunes are called embryo dunes and these may be colonised by pioneer species which make the conditions less hostile, such as marram grass. The plant roots stabilise the dune and the decaying plant matter adds organic content to the sand which aids water retention- embryo dunes are only 1m high and around 80% exposed sand
4- as the dunes grow they become out of reach of high tide and are known as yellow dunes- yellow dunes are about 5m high and are about 20% exposed sand
5- as more sand accumulates and plants continue to grow and add organic matter to the dunes they become fixed and ‘grey’ as the humus (organic content) increases- grey dunes tend to be 8-10m high and are less than 10% exposed sand. They are also able to support larger plants which require more water and organic matter such as as gorse bushes
6- dune slacks may form between the dunes where the water table is at the surface; in these ponds aquatic ecosystems form
7- inland from the grey dunes you find mature dunes or dune heath/woodland. Here, hardy trees such as birch and shrubs like gorse and heather grow which further increase humus levels, moisture retention and decreases the PH- this final stage in succession = CLIMAX VEGETATION

Question 56

Give an example of where there are sand dunes

Answer 56

Range of sand dunes around the UK, the largest ones on the West coast. Example is Studland Bay near Southampton

Question 57

Regarding estuarine landforms what do we need to know the formation of?

Answer 57

Formation of mudflat and salt marsh ecosystems

Question 58

What are mudflats?

Answer 58

Mudflats, also known as tidal flats, are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries

Question 59

What are salt marshes?

Answer 59

Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides (they are marshy because the soil may be composed of deep mud and peat)

Question 60

Discuss the background of mudflat and salt marsh ecosystem formation

Answer 60

• mudflats and salt marshes form on low energy coastlines and in areas of lower energy such as river estuaries where tidal currents are slowed down or behind spits where slack (low energy) water is found
• in estuaries or behind spits, slow flowing water from the river carrying lots of suspended sediment meets saline sea water which causes flocculation to happen as clay particles aggregate (stick together)
• these larger, heavier clay particles sink to the bed of the estuary
• at low tide in the inter-tidal areas this mud is exposed with water left flowing in channels between mudflats, and over time mudflats can become salt marshes

Question 61

Where are the largest mudflats and salt marshes in the uk found?

Answer 61

Morecambe Bay in Lancashire

Question 62

Just like with sand dunes, the formation of mudflats and salt marsh ecosystems can be described as a step-by-step sequence of succession:

Answer 62

1- vegetation like eelgrass begins to grow on the mudflats
2- this slows the currents down which leads to more deposition although it’s uneven according to where the eelgrass is
3- pioneer species (eelgrass is a sea-plant so doesn’t count as a pioneer species) begin to colonise the area and due to the conditions are halophytes (salt-tolerant) such as Spartina a.k.a cordgrass which is the dominant vegetation on UK mudflats as it has a fine mat of roots, which binds the mud together and thus traps more sediment
4- deposition continues as the plants continue to grow and die which raises the surface of the marsh- as this happens, the mudflats are submerged for shorter periods of time and the mudflat becomes a saltmarsh
5- more complex flowering species like marsh samphire become established as they are less tolerant of salt than the pioneers
6- more deposition occurs and and the vegetation becomes more dense which further raises the surface level and soil conditions improve
7- where the marsh rises about the level of spring high tide, trees and scrub start to grow = climax vegetation, the natural and end-point of succession

Question 63

In reality, why is it that often the climax vegetation isn’t reached? (Mudflat and salt marsh succession)

Answer 63

Farmers graze sheep on salt marshes