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Physical Geography > Coasts > Flashcards

Coasts Flashcards

1
Q

the littoral zone

A

The little zone is the zone of dynamic equilibrium with many inputs, processes and outputs causing rapid change. It consists of factual, for sure, near sure and offshore zones.

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2
Q

offshore

A

zone furthest out

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3
Q

nearshore

A

between the offshore and the foreshore: where the sea bed begins to slope upwards and flatten

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4
Q

foreshore

A

between the nearshore and backshore: swash and backwash zone

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5
Q

backshore

A

zone inland: the beach

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6
Q

advancing and retreating coasts

A

classifying coasts into advancing and retreating combines shorter-term erosion and deposition with longer-term changes in sea and land level. Resistant rocks (geology) can also reduce erosion, slowing the rate by which coast retreat down.

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7
Q

what’s the difference between a high and low energy coast?

A

The amount of energy in the coastal environment determines the coastal landscape.

Characteristics of high energy coasts:
– waves: more powerful waves (destructive), conditions, longer factors
– processes: erosion and transport; sediments from eroded land, mass movement and weathering, supplied by offshore current
– landforms: cliffs, wave cup platforms, arches, Caves, stacks.
– General location: exposed to largest waves, Highland and lowland coasts, Rocky landscape

Characteristics of low energy coasts:
– waves: less powerful waves (constructive), storm conditions, long fetches
– processes: deposition and transport; settlement from rivers, longshore drift and natural currents
– landforms: beaches, spit, bars, sand dunes, mudflats so washes
– general location: sheltered from large waves; lowland coasts, coastal plain landscapes

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8
Q

what effect does geological structure have on the type of coast?

A

geological structure determines whether the coasts are concordant or discordant, influences dalmatian and half coastline types (concordant) and headlands and bays (discordant), and the formation of cliff profiles (cliff cross sections) and microscale features (e.g. caves).

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9
Q

concordant coasts

A
  • concordant coast occur where the folding or arrangement of alternating hard and soft rocks is parallel to the coast (Dalmatian coastline type)
    – this means more resistant rocks form elongated islands, while less resistant rocks from long inlet or coves.
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10
Q

discordant coasts

A

– Discordant coasts occur where the folding or arrangement of alternating hard and soft rocks is in right angles to the coast (Atlantic coastline type)
– this means more resistant rocks for headlands, while less resistant rocks form bays or inlets

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11
Q

haff coastline

A

these are a type of concordant coastline found on the southern Baltic coastline. Long ridges of mud and sand form parallel to the shoreline, with lagoons (haffs) behind them.

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12
Q

headlands and bays

A

wave refraction explains why headlands are eroded more than bays: wave energy is focused on headlands and reduced in bays. Overtime the coastline ‘smooths’.

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13
Q

cliff erosion diagram

A
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14
Q

what do rates of coastal erosion depend on?

A

Rates of coastal recession and stability depend on bedrock lithology, differential erosion and – on Sandy Coast – the role of vegetation.

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15
Q

lithology

A

rock types and their characteristics

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16
Q

how does lithology influence coastal recession?

A

– Igneous rocks (e.g. granite) are more resistant to erosion and weathering than less resistant sedimentary rocks (e.g. limestone)
– Metamorphic rocks are formed from sedimentary and igneous rocks subjected to intense heat and pressure (e.g. marble), making them more resistant.
– superficial deposits made by rivers, wind and glaciers can overlay bedrock. These are unconsolidated and usually easily eroded.

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17
Q

strata

A

layers of rock

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18
Q

what is differential erosion?

A

cliffs can have alternating strata of different rock types, with differing resistance to weathering and erosion. This makes for a complex cliff profile and influences recession rates because erosion happens at different rates.

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19
Q

what influences differential erosion?

A

– A cliff with a permeable rock strata above an impermeable, weekly consolidated rock strata is vulnerable to mass movement. This is because rainwater is percolating into the upper strata creating instability.
– some types of rock contains soluble minerals of vulnerable chemical weathering
– strata of rocks may erode faster than other strata, as chemical weathering gradually weakens the rock

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20
Q

what is the stabilising role of vegetation?

A

– Plant roots bind the sediment together so they are less likely to be eroded.
– plant leaves slow down windspeeds at ground level reducing erosion and increasing deposition.
– as plants lose leaves and as they die they add organic material to the sand which eventually forms soil

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21
Q

what is plant succession?

A

succession refers to the way the vegetation on a sandy coastline changes overtime, from pioneer species, which initially colonise the bare sand or mud, to the climax seal stage.

– Plants especially adapted to the salty conditions (they are halophytes) and the dry conditions and rapidly draining sand dunes (they are xerophytes)
– sand and salt marshes both have plants succession that stabilise the soil

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22
Q

what are halophytes?

A

plants that are specially adapted to salty conditions

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23
Q

what are xerophytes?

A

plants specially adapted to sandy conditions (dry)

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24
Q

what are the stages of dune succession? what vegetation do you find at each stage? could be useful to draw a diagram and fill in anything missing.

A
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25
Q

how is the effectiveness of marine erosion determined? (what factors make an area around the sea erode… essentially what causes the erosion?)

A

– Wave type
– wave size
– tide level
– the shape of the coastline and lithology of the rock
– the mineral composition
– angle of bedding
– jointing of a rock

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26
Q

how are waves formed?

A

– Waves result from friction between the wind and the sea surface.
– the potential energy of a wave is proportional to its height

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27
Q

destructive waves

A
  • backwash is stronger than swash, removing sediment from the beach
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28
Q

constructive waves

A
  • swash is stronger than backwash, depositing sediment on the beach
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29
Q

what are the 4 wave erosion processes?

A

Attrition
Abrasion
Corrosion
Hydraulic action

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30
Q

attrition

A

waves continually move rocks, pebbles, and sand, especially in the surf zone. As the sediments move, projecting angular corners are knocked away producing stones.

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31
Q

abrasion

A

destructive waves pick up sand and pebbles (or larger rocks) and scrape or throw them against the rock, abrading it.

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32
Q

corrosion

A

water from waves may react with rock minerals and dissolve them. The minerals are carried away in the seawater.

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33
Q

hydraulic action

A

A large destructive wave breaking on a cliff exerts considerable pressure. May be compressed into cracks or joints in the rock. The sudden release of pressure can shatter the rocks.

34
Q

how can you measure waves? (like literally if you want to know frequency or something)

A

Time the frequency of the waves over effect period using a stopwatch to time the gap between the arrival of each wave crest. Use a fixed point on the beach to give a reference point. This would give you the data for a measure of central tendency. The main frequency of the waves would tell you if they were constructive or destructive.

35
Q

formation of a wave cut platform

A
36
Q

cave arch stack stump sequence

A
37
Q

what is a sediment cell?

A

> along the section of coastline, erosion, transport and deposition processes operate in a linked system.

– a sediment cell has sources, transfers and sinks: in theory it is a close system
– erosion in one place in the system (the source) is balanced by deposition in another (a sink), with transfers of sediment within the cell by processes such as longshore drift and current
– the amount of sediment gained from sources and loss to sinks can be calculated: sediment budget.
– It is a useful concept for assessing the extent of coastal change and for a evaluating coastal management strategies

38
Q

how many sediment cells are there in the UK?

A

11

39
Q

sediment cell example

A
40
Q

sediment cell sources, transfers and sinks

A

sources: erosion of cliffs, land sediments transported by rivers, wind-blown sediment from the land, onshore currents bringing sediment to shore

transfers: long shore drift, waves, tides, currents and wind

sinks: depositional features on the backshore (dunes), foreshore (beaches) and nearshore (bars) and offshore

41
Q

dynamic equilibrium in a sediment cell

A
  • negative feedback tends to maintain equilibrium, for example where wave erosion causes rockfalls, which then protect the base of the cliff from further erosion.

– positive feedback tends to increase change in the system into a new equilibrium is reached, for example a ‘blowout‘ in a sand dune allows more sand to be eroded by the wind, reducing vegetation cover further.

42
Q

longshore drift

A
  • the strongest longshore drift occurs when waves approach the beach at a 30° angle
  • The swash carries beach sediment up the beach at the same angle as the waves approach.
    – the backwash carries the sediments back down the beach at right angles to the shore, under the influence of gravity. This moves sediment along the coastline until it meets an obstacle
    – the predominant wind direction determines the direction of longshore drift.
43
Q

transport process landforms

A
44
Q

types of weathering

A
45
Q

what are the 3 types of weathering processes?

A

mechanical
chemical
biological

46
Q

what are subareial processes?

A

a combination of weathering and mass movement that alter the shape of the coastline

47
Q

what is mass movement?

A

– Mass movement is the movement downslope of rocks, sand, clay or soil.
– it is caused by gravity once a slow post become unstable: after waves have undercut resistant rocks or when water enters unconsolidated rocks and forces particles apart
– water content determines the type of mass movement
– slope angle and vegetation is also important in determining slope stability

48
Q

mass movement landforms: Talus scree slopes

A
49
Q

mass movement landform: rotational scars and terraced cliff profiles

A
50
Q

mass movement landform: block falls

A
51
Q

mass movement landform: mudflows

A
52
Q

what is eustatic change?

A

a change in sea level

53
Q

what is isostatic change?

A

a change in the land level - also linked to ice on the land

  • when ice is km thick, its weight pushes the land down
  • britains north was glaciated and pushed down, the south was ice free and so tilted up
  • when ice sheets melted at the end of an ice age, the land that had been pushed down rebounded back up and land that tilted up started to sink back; this is called post glacial adjustment
  • sediment eroded from sinking land will be redeposited on coasts; this is called accretion
54
Q

what is post glacial adjustment?

A

when ice sheets melted at the end of an ice age, the land that had been pushed down rebounded back up and land that tilted up started to sink back

55
Q

tectonic change

A

– As tectonic plates moving and collide, some continental shelves and areas of land are pushed upwards, or sink downwards.
– volcanic islands may create new coast lines, for example island arcs
– tectonic activity can produce tsunamis, which threaten coastal areas

56
Q

emergent coastlines

A

these are often the result of isostatic rebound:

– Raised beach: a form of beach that is now above the high tide line. Some raised beaches may consist of several different levels, each indicating different stage of uplift. Features such as rounded boulders and pebbles may be present.
– Fossil cliffs: near-vertical slopes initially formed by marine processes but now found some distance in land. They may still have visible marine erosion features such a sea caves and wave-cut platforms

57
Q

submergent coastlines

A

submarine coasts are often the result of sea level rise or isostatic sinking.

– A ria is a flooded river valley. The valley sides may be steep due to their being formed in periglacial conditions, when the soil was frozen.
– a fjord is a flooded glaciated (U-shaped) valley: very deep water with steep sides
– Dalmatian Coast are concordant coast where the sea has flooded the landscape of alternating hills and valleys create long bays and parallel hilly Islands.

58
Q

climate change and sea level rise

A

– As the sea heats up, it’s volume increases (thermal expansion). This currently contributes to over 50% of sea level rise.
– in the future, melting ice from glaciers, Greenland and Antarctica could increase sea level rise significantly.
– The rate of sea level rise is increasing as the ocean warm and polar ice melting exceeds expected rates.
– erosion rate and coastal change will be intensified by climate change and sea level rise

59
Q

what are 3 possible coastal impacts of climate change?

A
  • low lying islands and eco systems will disappear
  • stronger storms will create larger more destructive waves causing increased erosion
  • wave height will increase in the arctic as sea ice disappears causing increased erosion
60
Q

how do human actions affect the sediment cell system?

A
61
Q

what is rapid coastal recession?

A

coastal recession (retreat) is the result of natural factors such as geology, marine processes and sub-aerial processes.

Human actions can sometimes alter these processes.

62
Q

what physical factors affect rapid recession?

A
63
Q

what local factors increase the risk of coastal flooding?

A
  • height of an area
  • degree of subsidence (isostatic sinking)
  • vegetation removal
64
Q

why do humans live on the coast

A

sea and river trade
farming (deltas have very fertile soil)

65
Q

how do mangroves reduce coastal flooding

A
  1. they reduce the height of the waves reducing wave erosion at the coast
  2. their roots trap sediment raising the height of the coast
  3. they reduce storm surge levels - by 0.5m for every 1km of forest the seawater has to pass through
66
Q

what are storm surges and how do they form

A

storm surges are linked to low pressure weather systems, particularly tropical cyclones and depressions.

  1. Low air pressure over the sea allows water to bulge upwards in a dome.
  2. The lower pressure, the higher the dome
  3. Storm surges are made worse by wins on top of the jam, which increases the height of the water at the coast, increasing the risk of flooding.
  4. When the low pressure system moves towards the coast, the dam of seawater surge of shore.
  5. The shape of the coastline can also increase storm surges if it acts to funnel storm towards an area of shallow offshore water.
67
Q

consequences of coastal recession: economic

A

these include cost of repairs and rebuilding, loss of jobs and income and the money and resources needed in form of aid

– in the UK the government does not pay compensation to people who lose their homes to coastal erosion.
– most coastal erosion happens over a long period of time and affect where to be few people. The properties affected lose their value.
– sudden economic losses from coastal recession to happen but rare.

68
Q

consequences of coastal recession: social

A

these are the losses directly affecting people, for example having to relocate temporarily or permanently or losses of amenity areas.
– Coastal recession can produce a less aesthetically attractive coastline with boarded up properties and closed roads. - – Coastal recession can lead to conflict: example of people experiencing coastal erosion blame the construction of seed defences up drift
– living with coastal erosion can impact on health because of stress of property losing value, insurance increases, etc

69
Q

how many environmental refugees are there and how will this change going into the next few decades?

A

– Around 22.5 million people have been displaced due to climate related events between 2008 and 2016.
– a world bank study estimated that more than 100 million people will be pushed into poverty by climate change by 2030
– rising sea levels are a major factor for example by 2050 years estimated up to 18 million people may be displaced in Bangladesh by rising sea levels

70
Q

what are some different hard engineering strategies?

A
71
Q

what are some different hard engineering strategies?

A
72
Q

what are some different soft engineering strategies?

A
73
Q

what are some features of sustainable management?

A

– The full environmental impact of new developments on the coast needs to be evaluated before developments can proceeded.
– waste in coastal environments needs to be minimised.
– everyone affected by new developments on the coast needs to be involved in the decision making about the developments
– new economic developments on the coast should provide some benefits for the local community.
– the exploitation of coastal resources must be avoided.
– working with physical processes where possible to reduce unsustainable spending on hard engineering coastal defences
– adaptation to future changes/threats

74
Q

what is managed retreat and how does it work?

A

Ministry is an example of a sustainable approach to coastal defence in areas where costs of hard or soft engineering significantly exceeds the benefits. This may conflict with the wishes of local people.

How it works:
areas a set aside for the C2 Flood or a road. For example, for assault marshes that are now farmland may be allowed to flood again.

Benefits:
– can avoid the construction and maintenance costs of hard engineering.
– can stand valuable and natural ecosystems
– and adaptation response to sea level rise

Costs:
– requires the agreement of affected landowners and property owners.
– may only be medium term solution if sea levels continue to rise further.
– defences often need to be constructed around the edge of the flooded area to protect property

75
Q

what are some adaptation strategies

A
  1. restoring mangroves: effective against storm surges, boost fish numbers, benefit local communities.
  2. Zoning areas of coast: threatened by sea level rise to prevent further development there which avoids increasing risk
  3. elevating critical infrastructure: for example power stations to protect them from flooding
76
Q

what is ICZM and what does it do?

A

ICZM stands for integrated coastal zone management.

– A process for planning and coordinating how coastal resources are used and developed.
– integrated means it looks at the coast as a whole system and brings together all of the stakeholders with the aim that everybody benefits including human and physical marine and terrestrial processes.
– coastal zones are littoral cells which is a similar concept of sediment cell

77
Q

what is ICZM and what does it do?

A

ICZM stands for integrated coastal zone management.

– A process for planning and coordinating how coastal resources are used and developed.
– integrated means it looks at the coast as a whole system and brings together all of the stakeholders with the aim that everybody benefits including human and physical marine and terrestrial processes.
– coastal zones are littoral cells which is a similar concept of sediment cell

78
Q

what are SMPs and what do they do

A

SMP stands for shoreline management plan

– SMP‘s are examples of ICZM
– there is an SMP for each littoral cell.
– putting together an SMP involves consultation with scientific advisors and many groups of local stakeholders: resident associations, landowners, farmers, wildlife organisations, local leisure clubs, local tour sports, chamber, and utility companies
– S&P identify the risk associated with coastal processes operating in the littoral cell and make decisions about how to manage them

79
Q

what is an SMP coastal defence evaluation and what are the 4 policy choices?

A
80
Q

what are some implications of policy decisions?

A

Some places have seen an SMP policy decision change from holding the existing shoreline to no active intervention or manage retreat.
– this usually followed a cost benefit analysis: comparing the cost of coastal defences with the value of the land be protected.
– places with low lying land had difficulty qualifying for government money to pay for sea defences.
– this affected property values in these places and also had social impacts – communities felt less secure

81
Q

what are some factors affecting policy decisions?

A

although the economic value of the land is often the most significant factor and decisions to hold the existing shoreline, there are others:
– coastal sites that have strategic importance for national infrastructure, such as nuclear power stations or gas terminals
– coastal areas with historical sites, areas of archaeological significance are important cultural value
– coastal areas that provide habitats for rare plants and animals.
– places that mount effective publicity campaigns for coastal protection or effective lobbying of their MP

82
Q

what is coastal management in developing countries and how can it be challenging?

A

coastal management is challenging where:
– coastal erosion is rapid.
– coastal communities are vulnerable because of poverty and lack of opportunity.
– local people have no legal rights to the coastal land they depend on.
– coastal regions are controlled by elites who look after their own interests only

Physical Geography (4 decks)

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