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Geography Revision > Coasts > Flashcards

Coasts Flashcards

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1
Q

What are the subdivided areas of the littoral zone?

A
  • offshore - beyond the influence of breaking waves
  • nearshore - intertidal and within the breaker zone; used for fishing, trade and leisure
  • backshore - above high tide and the influence of normal wave patterns; may have a storm beach further up
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2
Q

Rocky coasts key points

A
  • subject to erosion
  • tend to be steep or vertical in profile
  • attacked by weathering and mass movement processes
  • often a high energy environment
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3
Q

Plain coasts key points

A
  • deposited landscapes of sand, shingle and mud
  • low, flat landscapes, often poorly drained
  • often a low energy environment
  • dominated by processes of accretion so the coastline advances seaward
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4
Q

What are the three elements to geological structure?

A
  • Different layers of rock exposed in a cliff - strata
  • Degree of tilting and folding by tectonic activity - deformation
  • Fracturing that may have moved rocks from their original positions - faulting
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5
Q

What are the two types of coast the geological structure produces?

A
  • Concordant - when rock strata run parallel to the coastline
  • Discordant - when different rock strata intersect the coast at an angle so rock type varies along the coastline
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6
Q

Concordant coast example

A
  • The Dalmation Coast in the Adriatic sea:
    • limestone been folded by tectonic activity into a series of anticlines and synclines that trend parallel to the sea
    • the syncline basins have been drowned by sea level rise
    • the anticlines have produced long narrow offshore islands
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7
Q

Discordant coasts key points

A
  • Dominated by headlands and bays
  • Less resistant rocks are eroded to form bays
  • More resistant rocks remain as headlands protruding into the sea
  • Headlands and bays change over time because headlands are more eroded than bays - due to refraction
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8
Q

What is wave refraction?

A
  • in deep water wave crests are parallel
  • as water becomes shallower waves slow down and increase in height
  • in bays - wave crests curve to reflect their shape and wave height increases
  • wave action is concentrated on headlands
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9
Q

What are cliff profiles affected by?

A
  • resistance of rock to erosion

- dip of rock strata

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10
Q

Other geological features influencing cliff profiles and can intiate notches and caves

A
  • faulting can expose rocks to erosion as they are areas of weakness
  • natural cracks in rocks (jointing) can also be areas of weakness
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11
Q

Key points of stability

A
  • vegetation roots bind sediments together making them more resistant to erosion
  • when submerged plants protect the surface from erosion
  • plants also protect sediment from wind erosion by reducing wind speed through fraction
  • plants that grow as a succession in coastal environments are specially adapted xerophytes or halophytes
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12
Q

Key points about sand dunes

A
  • sand is deposited by the sea in low energy conditions
  • wind may then move the sand to make dunes further up the beach
  • these in turn become colonised by stabilising plants
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13
Q

Key points about salt marshes

A
  • sheltered river estuaries or zones in the lee of spits are areas where there are extensive accumulations of silt and mud aided by flocculation and gentle tides
  • these intertidal areas are colonised by vegetation and over time this may develop into a salt marsh
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14
Q

What is wave energy controlled by?

A
  • the force, direction and duration of wind

- the fetch - the longer the fetch the more energy a wave has

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15
Q

How do beaches change over time due to the types of waves?

A
  • daily - as a storm passes destructive waves become constructive and berms are created
  • seasonally - storm beaches created mostly in winter
  • long term - more storms may occur due to climate change with higher storm beaches
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16
Q

What is the rate of coastal erosion affected by?

A
  • lithology - harder rock is more difficult to erode - some resistant rock can be eroded along joints or cracks
  • structure and dip; steep cliffs form if rocks dip inland whereas rocks that dip seaward produce gentler slopes
  • wave steepness; steeper, high energy waves have more power to erode
  • wave breaking point; waves breaking at the foot of a cliff have more energy to erode
  • width of beach - wider beaches absorb some of the waves energy and protect the coastline
  • nature of the beach; pebbles dissipate energy from waves through friction and percolation
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17
Q

Cliffs, headlands and bays key points

A
  • form when rocks of differing hardness are exposed together at a coastline
  • tougher, more resistant rocks tend to form headlands with cliffs
  • weaker rocks are eroded to form sandy bays
18
Q

Wave cut platforms key points

A
  • consist of rocks that are gently seaward sloping
  • have an irregular surface
  • overhanging rocks may collapse causing the cliff to retreat and the wave cut then lengthens
  • allows waves to break at the foot of the cliff causing max erosion at this point
  • found between high and low tide which causes friction for waves
19
Q

Caves/arches/stacks key points

A
  • erosion takes place on a cliff face where there is weakness
  • smaller hollows can be excavated to create caves
  • where caves are created on either side of a headland and are eroded back they can meet each other and from an arch
  • the sea is now able to splash under the arch further weakening and eventually the roof collapses leaving a stack
  • over time the stack erodes into a stump
20
Q

Key points of sediment cells

A
  • coastlines operate as sediment systems with sources, sinks, transfers, budgets and feedback mechanisms
  • they seek a dynamic equilibrium
  • sediment sources are rivers, the sea bed, erosion of the coastline and shell material
  • there are 11 cells in England and Wales with some in sub-cells
  • each cell is seperated by headlands or stretches of water
  • sediment cells are a key component of shoreline management plans
21
Q

Positive feedback points

A
  • sea walls may prevent flooding but they also limit cliff erosion
  • this restricts the release of sediment into the system
  • this sediment might otherwise have been re-deposited so helping to protect the coastline
22
Q

Negative feedback points

A
  • sediment is eroded from a beach during a storm and is then deposited offshore to form a bar
  • waves break before reaching the beach dissipating their energy and therefore reducing erosion of the beach
  • normal wave conditions rework offshore deposits back to the beach
23
Q

Changes in sea level take place over the longer term due to …

A
  • sea temperatures being colder or warmer than at present

- relative changes in levels of land

24
Q

Eustatic change…

A
  • results from a fall in sea level due to a new glacial period when water is held as ice
  • also results from a rise in sea leel when at the end of glacial period the ice on land melts
25
Q

Isostatic change ,…

A
  • arises from changes in local relationship of land to sea
  • as ice collected on the land during glacial periods the extra weight pressed down on the land causing it to sink and sea level to rise
  • as the land ice melts the land begins to move back up to its original position and the sea level falls
  • depends on the thickness of the original ice and the speed of its melting
26
Q

Emergent coastlines points

A
  • falling sea levels expose land that is normally covered by the sea
  • cliffs that are no longer being eroded become isolated from the sea, leaving fossil cliffs
  • fossil features - eg - former caves are left higher up from the shoreline
  • raised beaches occur as a series of sandy and pebble strewn terraces well above current sea levels
27
Q

Contemporary change points

A
  • the IPCC predicts that sea level could rise by 98cm by 2100 as a result of climate change
  • sea level can change locally due to tectonic forces
28
Q

What physical factors affect rapid coastal retreat?

A
  • large destructive waves with a long fetch
  • cliffs with structural weaknesses
  • strong longshore drift
  • cliffs vulnerable to mass movement and weathering as well as marine erosion
29
Q

Human factors in rapid coastal retreat

A
  • reducing sediment input by constructing dams on rivers

- dredging sand and gravel from the sea bed

30
Q

Rates are influenced by

A
  • weather related factors - season type, storms, wind direction
  • physical factors - relative hardness of rocks, rates of weathering
  • human factors - coastal management schemes
31
Q

Why are some coastal areas at high risk of flooding

A
  • around estuaries or on deltas with very low altitudes
  • subject to storm surges
  • in delta regions so water comes from inland as well as the sea
  • where protective mangrove forests have been cleared
  • where rivers have been straightened to speed up river flow
  • in areas where coastal topography funnels water from surges and/or high tides
32
Q

Why is the number of environmental refugees likely to increase?

A
  • rising sea levels
  • more intense storms and secondary events
  • coral reefs being attacked by bleaching
  • salt water incursion into freshwater supplies
33
Q

Hard engineering definition

A

a form of coastal management that involves the construction of man made features

34
Q

Soft engineering definition

A

a form of coastal management that involves working with natural features

35
Q

Conflict may come from coastal management from..

A
  • managing natural resources to ensure long term productivity
  • managing flood and erosion risk - relocation to safe areas
  • monitoring coastal change
  • educating communities to understand why change is needed
  • creating alternative livelihoods before existing ones are lost
  • adapting to sea level rise - relocating/building methods
36
Q

What does intergrated coastal zone management require?

A
  • recognition of importance of littoral zone to people’s livelihoods as large numbers of people live and work at the coast
  • recognition that management of a littoral zone must be sustainable - economic development should improve the QOL of people and this needs to be environmentally appropriate
  • that an entire littoral zone is managed not just the narrow zone where waves cause erosion or flooding
37
Q

Shoreline management plans points

A
  • introduced in 1995
  • don’t exist in Scotland
  • an approach to coastal management that involves all stakeholders in making decisions about how risks like flooding should be managed
  • predict, so far as it is possible the way in which a coastline will be shaped in the future
38
Q

What are the 4 coastal zone management policies?

A
  • hold the line - maintaining level of protection
  • advance the line - building new defences seaward
  • no active intervention - no investment in defences
  • managed realignment - allowing retreat of the shoreline
39
Q

What does making a decision about which policy to use depend on?

A
  • economic value of the land thats protected
  • cultural and ecological value of land
  • technical feasibility of engineering required
  • the attitudes of and pressure from local communities
40
Q

Why is the coastal erosion rapid in the developing world?

A
  • inland dams reducing sediment supply and disupting local sediment cells
  • rapid unplanned coastal development
  • destruction of mangrove forests exposing coastlines
41
Q

The general outcomes of this is…

A
  • losers - farmers and fisherman with no legal claims to land
  • winners - TNCs - eg - developers

Geography Revision (8 decks)

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