coastal landscape development Flashcards

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1
Q

name 3 erosional landforms

A
  • cliffs/wave cut platforms:
  • headlands and bays;
  • cliff profile features: caves, arches, stacks:
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2
Q

name 6 depositional landforms

A
  • beaches:
  • spits:
  • offshore bars/tombolo
  • barrier islands
  • sand dunes
  • estuarine/mudflats/saltmarsh

-forms in sheltered environments( spits, bars, bays, coves)

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3
Q

what is eustatic sea level change

A

sea level change caused by a change in the volume of water or a change in the shape of the ocean basins with global causes

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4
Q

what causes eustatic sea level change

A

-climate change: increase in temperature causing melting of ice sheet which increases sea level
a decrease in temperature which causes more snow which increases the the water stored in glaciers which reduces the volume of the sea and decreases sea level

  • tectonic movements: movements in the crust alter the shape of the earth basins
    e. g. sea floor spreading increases the volume of the basin and so decreases sea level
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5
Q

what is isostatic sea level change

A

sea level change caused vertical movements of the land relative to the sea with local causes

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6
Q

what causes isostatic sea level change

A
  • uplift: the melting of ice sheets causes land to slowly lift up over thousands years due to the removal of weight - -isostatic rebound:
  • depression: the accumulation of ice sheets causes a depression due to the new weight
  • subsidence: land sinks when ground water is absorbed
  • tectonic: tectonic plates e.g. the subduction of one plate under another
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7
Q

5 points on sea level change in the past 10,000

A
  • last glacial maximum sea level was 130m lower than it is presently
  • the last time sea levels were this high was 4000 years ago
  • sea level rising since 1930
  • currently sea level rise per year =2mm
  • predicted for sea levels to rise 8-26mm per year by 2100
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8
Q

5 impacts of sea level change in the future

A
  • submergence of low lying islands e.g.0.5 increase in sea levels would completely submerge the Maldives
  • changes to coastlines-0.3m sea level rise will result in the lost of 8000km squared of land in Bangladesh’s
  • contamination of water sources and farmland
  • cause mass migration - international/rural-urban
  • displacement
  • cultural loss
  • soil problems - food security
  • increase in the intensity and frequency of storms
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9
Q

3 landforms of emergence caused by sea level fall

A
  • raised beaches: formed when sea level fall leave beaches above tide marks leaving a beach below. the raised beach will become vegetated overtime
  • marine platforms: sea level fall exposes wave cut platforms leaving them raised above their former levels
  • relict cliffs: cliffs above raised beaches which also become vegetated, erosional landforms are often still present.
  • e.g. occur in North Scotland
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10
Q

3 landforms of submergence caused by sea level rise`

A
  • rias: formed where river valleys are partially submerged. they are wide at mouths and become narrower as you go inland
    e. g. Milford haven, south wales

-fjords: formed when rising sea levels flood deep glacial valleys to create natural inlets and
harbours. They are deeper in the middle than they are at the mouth , with the shallower section
showing where the glacier left the valley
-e.g. Milford Sound New Zealand

-Dalmatian coasts: formed by sea level rises in areas with with valleys that are parallel to the coast. the valleys are flooded leaving island parallels to coastline

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11
Q

how are cliffs and wave cut platforms formed

A
  • Erosion is concentrated around the high-tide line creating a wave-cut notch
  • As the notch becomes deeper the cliff face becomes unstable and collapses
  • This leaves behind a platform of the unaffected cliff base
  • Over time a wave-cut platform is formed
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12
Q

how are headlands and bays formed

A
  • formed where bands of alternating hard and soft rock are at a right angle to the shore (discordant coastlines
  • soft rock is eroded quickly creating bays’
  • hard rock is more resistant and erodes less so it sticks out forming a headland
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13
Q

how are cliff profile features formed

A
  • weak joints in cliffs are eroded to form caves
  • caves on opposite sides may join or the cave is eroded through to create an arch
  • when the arch collapses a stack is formed
  • overtime erosion will turn a stack to a stump
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14
Q

how are beaches formed

A

-beaches are stores in the coastal system formed by the deposition of sediment on shore by constructive waves

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15
Q

features of a beach

A
  • berms: ridges of sand and pebbles found at high tide marks
  • runnels: grooves in sand running parallel to shore formed by backwash
  • cusps: crescent shaped indentations
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16
Q

how are simple, recurved and compound spits formed

A
  • spits form when the coast suddenly changes direction, e.g. river mouth
  • simple: long shore drift continuous to deposit material across the river mouth leaving a bank of sand sticking out.
  • recurved: a change in dominant wind direction will cause a spit to have a curved end
  • compound: over time recurved ends will be abandoned and new ones created due to changes in wind direction
  • the area behind a spit is sheltered from waves and so develops into a mudflats or saltmarshes
17
Q

how are offshore bars and tombolos formed

A
  • bars: formed when a spit joins two headlands together across a bay or river mouth. a lagoon will form behind the bar
  • offshore bars form of the coast and can be partially or fully submerged by sea level rise
  • tombolo: a bar that connects an island to shore
18
Q

how are barrier islands formed

A
  • A barrier beach is usually formed as an extension to a spit and joins two headlands together
  • Colonization by vegetation can stabilize the barrier beach and trap further sediment keeping it above sea even at high tide
  • when a barrier beach separates from the main land it becomes a barrier island
19
Q

how are sand dunes formed

A
  • sand deposited by longshore drift is moved up the beach by wind and trapped by driftwood and berms.
  • the sand is then colonised by vegetation which stabilises it and encourages more sand to accumulate creating embryo dunes
  • overtime dunes migrate inland allowing space for new embryo dunes
  • oldest dunes/grey dunes can reach 10m
20
Q

how are Estuarine mudflats and saltmarshes formed

A
  • Sediment is transported from the river and sea with suspension as the tide goes in and out
  • combination of fresh and saline water
  • Deposition occurs as a result of flocculation , leading to mud above the high tide level.
  • Pioneer plants (Barren sand, lyme grass, sea crouch grass) colonizes the transition zone, leading to more sediment becoming trapped.
  • A meadow is formed as sections of the salt marsh rise above the high tide level.
  • This leads to the climatic climax of the vegetation succession when trees begin to colonizes the area.
  • e.g. Morecomb Bay is the biggest Mudflat in England
  • e.g. Thames Estuary
21
Q

past impacts of sea level change

A

-increase in severe coastal flooding e.g. kings point, New York: 1995-2004 flooded 80 times
2005-2014 flooded 160 times

  • past millennia: sea level rise of 1-2mm per year
    now: 4-5mm rise per year
  • Banda Aceh, 2004 Boxing Day tsunami
  • earthquake caused the ocean floor to rise by as much as 40m
  • killed 230, 000 in 14 countries