Topic 2 - Marine processes Flashcards

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1
Q

What is hydraulic action?

A
  • The sheer force that water exerts as it crashes against a coastline
  • When a wave advances, air can be trapped and compressed, either in joints in the rock or between the breaking wave and cliff
  • When the wave retreats, this continous process can weaken rocks and cracks in the cliff, causing pieces of rock to break off
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2
Q

What is cavitation?

A
  • Simultaneously, bubbles formed in the water may implode under the high pressure
  • This generates tiny jets of water which will, over time, erode the rock
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3
Q

What is wave quarrying?

A
  • The action of waves breaking against unconsolidated material, such as sands and gravels
  • Waves scoop out the loose material in a similar way to the action of a giant digger in a quarry on land
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4
Q

What is abrasion/corrasion?

A
  • When waves advance, they pick up sand and pebbles from the seabed
  • When they break at the base of the cliff, the transported material is hurled at the cliff foot - chipping away at the rock and have a ‘sandpaper’ effect
  • The size, shape and amount of sediment along with the type of work, determines the relative importance of this erosive process
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5
Q

What is solution?

A
  • Weak acids in seawater can dissolve alkaline rock, or the alkaline cement that bonds rock particles together
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6
Q

What is attrition?

A
  • The gradual wearing down of rock particles by impact and abrasion as pieces of rock are moved by waves, tides and currents - this makes stones rounder and smoother
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7
Q

How does lithology affect coastal erosion?

A
  • Tough resistant rocks, erode at very slow rates compared to weaker clay and shales
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8
Q

How do waves affect coastal erosion?

A
  • Wave steepness - high energy waves
  • Breaking point
  • Fetch
  • Sea depth
  • Coastal configuration - headlands attract wave refraction via reflection
  • Beach presence
  • Human activity
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9
Q

How does geological structure affect coastal erosion?

A
  • Cracks, joints, bedding planes and faults create weaknesses in a cliff that can be exploited by erosive processes
  • Rocks, such as limestone, are well jointed, which means sea can penetrate along the lines of weakness, making them vunerable to erosion
  • The dip of the rock is also a major factor - the steepest cliffs tend to have horizontal strata or dip inland, whereas those which dip towards the sea from gentle slopes
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10
Q

How does coastal management affect coastal erosion?

A
  • The presence of structures, such as groynes and sea walls, will have an impact on sediment transfer (and the build up of beaches) and the patterns of wave energy along a coastline
  • In trapping sediment moved by lsd, groynes may deprive beaches further down-drift of sediment input - furthermore, sea walls may deflect wave energy elsewhere along the coast - exacerbating erosion in these locations
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11
Q

What is the coastal transportation process?

A
  • Transfers sediment from one store to another
  • 4 major methods of transportation:
  • Saltation - small stones and pebbles are bounced along the sea bed
  • Traction - heavy rocks and boulders are rolled along the sea bed
  • Suspension - very small particles of sand or clay that are suspended in the water
  • Solution - takes place when material is dissolved in the water, it is invisible and does not color in water
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12
Q

How do subaerial processes affect coastal erosion?

A
  • Weathering and mass movement will weaken cliffs and create piles of debris that are easily eroded by the sea, potentially increasing erosion rates
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