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Geography - Coasts > Coasts > Flashcards

Coasts Flashcards

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1
Q

How can coasts be classified?

A
  • geological structure
  • concordant and discordant coastlines
  • sea level rising
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2
Q

what is a littoral zone?

A

A coastal zone which contains many coastal sediments. Waves, currents and tides move the sediment around in a zone.

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3
Q

What is dynamic equilibrium?

A

A system is in dynamic equilibrium when its inputs and outputs of energy and matter balance.

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4
Q

Backshore(1)

A

above the influence of waves - weathering and mass movements occur on the back-shore

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5
Q

Foreshore(2)

A

the inter tidal zone or surf zone

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6
Q

Nearshore(3)

A

the breaker zone

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7
Q

Offshore(4)

A

currents and longshore drift may move sediments some distance along the coast

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8
Q

Human activities can interfere with natural processes

A

dredging of offshore areas to get sand and gravel for construction
- the building for coastal defences against erosion and flooding

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9
Q

Classification of coats

A

sections of the coasts can be classified into different types using a variety of criteria, such as geology, sea level rise, and land level rise and fall , which causes long term changes, and erosion and depositions which causes short term changes . Advancing or retreating

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10
Q

inputs

A 
climate 
use of the beach 
marine 
storm surges
atmospheric weather
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11
Q

processes

A 
weathering 
transportation
depostion 
erosion 
mass movements
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12
Q

outputs

A

erosional landforms

deposition landforms

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13
Q

geological structures at different scales

A

the shape of the coast is largely determined by geology and wave action. various aspects should be considered such as resistance to erosion and weathering, which relates to the degree of consolidation (how well the rock is stuck together), the number of joints and bedding planes and the amount of folding. Wave characteristics include energy which is related to size and shape, length of fetch, the prevalent and direction of the wind.

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14
Q

Concordant coasts

A

occur where the folding or arrangement of rock types on the rock layers, lie in the same direction of the coast (parallel). Destructive waves hit the coast in the winter and result in hydraulic action and abrasion attacking weaknesses (faults and joints). eventually the waves erode through the less resistant clays. eventually the erosion slows down and the more resistant chalk layers are reached and a cove has been produced.
Adriatic sea is an example

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15
Q

Discordant coastline

A

occur when the folding or the arrangement of rock types on a large scale (macro) is at a right angle (perpendicular) to the coast. Alternating bands of hard and soft rock create headlands and bays or inlets where there is less resistant rock, or a down-fold,
South west Ireland is an example

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16
Q

How do headlands and bay form?

A

form on discordant coasts, waves eroding softer rocks faster than harder rocks. bays have a semicircular shape once eroded the waves in the bay dissipate , lose energy and deposit a bay head beach. the resistant rock forms rugged rocky headlands that stick out in the sea . Once this stage is reached the shape of the coastline causes waves to refract as they approach the headstand and this concentrates wave energy on them, increasing the rate of erosion.

  • headland and bays form when the layers of rocks are perpendicular to the coast - discordant coastline
  • wave action erodes the less resistant rock quicker due to hydraulic action and abrasion to produce bays
  • the more resistant rock is left cutting out as a headland. This causes incoming waves to refract (bend) and water becomes shallower (called wave refraction)
  • wave energy is now concentrated on the headland . waves become higher and steer, increasing erosive power on the headland.
  • the bay becomes sheltered as wave energy is dissipated
  • the result in the formation of beaches as sediment is deposited in the low energy
  • headland will finally erode to form a cave, arch, stack, stump.
17
Q

how are Dalmatian coasts formed?

A
  1. tectonic activity folded limestone layers are so that ridges (anticlines) and valleys (syndics) formed parallel to the coast.
  2. Sea level rose following the end of that the ice age and drowned the valleys (retreating a submergent coastline)
  3. The ridges remain as islands running parallel to the coastline
  4. Croation Dalmation coast
18
Q

How are Haff coasts formed

A

they form in low energy environments where there is deposition of muds and sands (long sediment ridges)- topped by sand dunes that run parallel to the coast - the build up has created lagoons -due to deposition on by onshore winds and low energy waves. Large lagoons are found behind the deposits parallel to the shoreline. The Baltic Sea coastline of Poland - Vistula Haff. They are on concordant run parallel to the coast e.g the south coast of the Baltic Sea

19
Q

How does geological stucture have an affect on the coastal morphology and erosion rates

A

tectonic forces may cause rock layers to fold into complex formations. e.g. the Stair hole ‘crumple’ at Lulworth in Dorset is thought to have been created by collision of the African and the eurasian plates. During the process of the rock formation, pressure and cooling may crack a rock to form crevices, joints or larger faults. Joints are made as sedimentary rock there are also usually bedding planes .

20
Q

lithology

A

refers to the physical characteristics of there rock . igneous, metamorphic, sedimentary and unconsolidated rock each have different charactersitics - this also influences the geological structure on a meso scale - sedimentary tends to be clearly defined layers.

21
Q

Metamorphic

A

well connected and impermeable

  • often folded and faulted so have weaknesses
  • this rock types create rocky coastlines with steep cliff profiles cliffs (depending on folding and dip )
    e. g. maybe, slate and schist
22
Q

igneous

A
  • their crystalline structure (interlocking crystals means they are well connected, impermeable and have few lines of weaknesses (joints)
  • these rock types create rocky coastlines with steep profiles cliff and erode very slowly.
    e.g. granite
    recession rates 0.1-0.3 cm/yr
    Lands End, Cornwall
23
Q

Less resistant rocks

A

often layers of permeable rock where water can remove the cement between the particles, high water pressure can reduce stability
sandstone erosion rate - 10-100 cm/yr
least resistant are unconsolidated rocks have not been cemented together
erosion rated 100-1000 cm/yr
(slumped coastlines due to mudslides/landslides and slumping

24
Q

sedimentary

A

limestone and chalk are relatively resistant but they are more vulnerable to erosion.
- clastics - made up of cemented sediment particles rather than interlocking spurs
- formed in strata (layers) with joints provided weaknesses and makes limestone permeable
- chalk is porous ( air spaces between them )
- can form wave cut platforms and under-cutting
- limestone erosion rate 1-2cm/yr
chalk 1-100cm/yr

25
Q

Factors affecting coastal recession - lithology *

A

bedrock lithology is important in deterring rates of coastal recession (retreat). , these are rock that make up the base of the land

26
Q

differential erosion

A

rocks with many cracks, joints and bedding planes, such as limestone, are permeable, means water can pass through the rock. rocks with spaces, or pores, such as chalk, are porous and also allow water to pass through. rocks that dot let water in the rock. the presence or absence of water may affect weathering and mass movements(collectively sub aerial processes).
rocks that do not let water pass though are impeprable e.g. granite.
soluble minerals in the rock would also increase the rate of erosion e.g. limestone which is soluble in rainwater

27
Q

how can coastal recession rates be determined

A

Coastal recession rates can be determined by examining historic maps and images over recent ones. - using modern technology such as Lidar (light detection and Ranging), not all recession is due to marine erosion: sea level rise and sinking land must be considered

28
Q

what can vegetation do?

A

vegetation can help to stabilises unconsolidated sediments at the low energy coastilnes based on sand and mud. helps reduce erosion at the coast

29
Q

what is the role of vegetation?

A

ecosystems at the coast include coral reefs, mangrove forest, salt marshes and sand dune

30
Q

what is plant succession?

A

over time, with pioneer plants colonising bare areas first. as they change the condition of the soil by adding humus (decayed vegetation) retaining moisture and stabilising loose sand or mud, new plants are able to establish themselves and take over. This keeps happening until there is a a balance between all the natural factors and the vegetations, when the climax - final negation type establishes itself.

31
Q

sand dunes and salt marshes

A

they are know as psammosere, where xerophytic plants scubas marram grass can survive with little fresh water. salt marshes are know as halophytic plants such as samphire that can survive in salty conditions. - important buffer zones between the sea and the land, with salt marshes absorbing coastal flooding and sand dunes taking the impact of storms.

32
Q

Facts about salt marhses

A

salt marshes are common in low energy environments of estuaries and sheltered bays. The tidal conditions bring seawater and sediments in and out. The tiny clays particles stick to one another - called flocculation , once deposited they are colonised by algae. Salt marshes can be found in creeks and at the end of estuaries, behind a spit . The pioneer plants have to survive being covered with slightly salty water twice a day. over time, the plants change the conditions by trapping more sediment, which builds up the salt marsh up to a higher level, so other plants can be colonised

Geography - Coasts (1 decks)

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