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Secondary 3 Geography > coasts gw 1 > Flashcards

coasts gw 1 Flashcards

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1
Q

what are coasts?

A
  • coast is area where land meets sea, covering land that is affected by waves and tides
  • coast can be cliffed, sandy, rocky, muddy
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2
Q

what are the factors affecting coastal environments?

A
  • waves
  • tides
  • currents
  • geology
  • human activities
  • types of ecosystem
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3
Q

how do waves affect coastal environments?

A

constructive and deconstructive waves

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4
Q

how do tides affect coastal environments?

A
  • affecting processes like coastal erosion, sediment transport and deposition
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5
Q

how do currents affect coastal environments?

A
  • longshore current helps transport sediments, giving rise to a sandy coast
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6
Q

how does geology affect coastal environments?

A
  • hard resistant rocks lead to less erosion and less resistant rock lead to more erosion
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7
Q

how does human activities affect coastal environments?

A
  • human activities create pollution and can affect a coast
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8
Q

how does types of ecosystems affect coastal environments?

A
  • mangrove systems or coral reefs can affect how a shore develops as they reduce the impact of waves on a coast
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9
Q

name the wave terminology

A

wave length is the horizontal distance from crest to crest or trough to trough
wave height is the vertical distance between crest and trough
wave frequency is number of wave crests or troughs that pass through a fixed point
wave steepness is ratio of wave height to wavelength
wave period is time waves take to travel through one wavelength
crest is highest part of wave
trough is lowest part of wave

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10
Q

what are the factors affecting wave energy?

A
  • wind speed
  • wind duration
  • fetch
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11
Q

how does wind speed affect wave energy?

A
  • the faster wind blows, the greater the wave energy
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12
Q

how does wind duration affecting wave energy?

A
  • wind duration because the longer the wind blows, the larger the waves are
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13
Q

how does fetch affect wave energy?

A
  • the distance over which the wind has travelled over seas and oceans to form waves affect wave energy because the greater the fetch, the more energy waves have
  • the higher the wave energy is, the steeper the wave and shorter it becomes
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14
Q

what are the characteristics of waves in the open ocean?

A
  • waves in the open ocean have a long wavelength and low wave height, particles in the ocean also move in an orbit
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15
Q

what are the characteristics of wave clost to the coastline?

A
  • do not move in an orbit
  • water close to the coastline is shallow and waves start to interact with the seabed, changing shape
  • as the waves continue travelling in shallow water, the base of the wave slows down due to friction
  • this causes wave ehight to increase and wavelength to decrease
  • eventually this reahes a point where the base of the wave stops but the wave crest becomes steeper and topples over
  • this causes the process of waves breaking onto the coast
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16
Q

what is swash?

A
  • formed when waves break and water rushes up a beach. Swash moves up the beach in direction of waves, carrying sediments with it
17
Q

what is backwash?

A
  • backwash is created when the swash loses energy due to gravity and friction to the sea and returns back to it, forming backwash. Backwash carries sediments from shore to the sea perpendicularly to the shoreline
18
Q

where do constructive waves occur?

A
  • low gradients, low energy environment

- occur on gentle coastal slope and sheltered coast

19
Q

where do destructive waves occur?

A
  • steep gradients, high energy environment

- occur on steep coastal slope and open coast

20
Q

what is the shape of oncsutrctive waves?

A
  • small, low waves

- low wave height, long wavelength

21
Q

what is the shape of destrcutive waves?

A
  • large high waves

- high wave height, short wavelength

22
Q

what is the frequency of constructive waves?

A
  • occur 6-9 per minute
23
Q

what is the frequency of destructive waves?

A
  • backwash more powerful than swash
  • erosion process more prominent
  • transport rocks and material away and erode coasts
24
Q

what type of coasts do constructive waves form?

A
  • gentle, sandy slopes
25
Q

what type of coasts do destructive waves form?

A
  • steeper, coarser slopes
26
Q

what is wave refration?

A
  • process in which waves change direction as they approach a coast
  • waves tend to converge on headlands, leading to a higher concentration of wave energy which means larger waves which are usually destructive, leading to enhance erosion
  • waves tend to diverge in bays. The dissipation of wave energy leads to smaller waves which are usually constrcutvie, leading to less erosion and more deposition
  • when they approach a straight coast at an angle, they break parallel to coast
27
Q

names the processes of coastal erosion

A
  • Corrosion
  • Attrition
  • Solution
  • Hydraulic action
28
Q

what is corrosion?

A

the impact of the sediments carried by the waves grinds against the rocks, weakening them and breaking them down

29
Q

what is attrition?

A

where the sediments in the wave hit and rub against one another, breaking into smaller pieces and becoming rounder and smoother

30
Q

what is solution?

A

where chemicals contained within sea-water may dissolve some rocks found on coast (e.g. carbonic acid against limestone)

31
Q

what is hydrualic action?

A

the impact of waves against the coast compresses air in between the rock’s joints and cracks and then releases it. This repeated action causes the joints to weaken and the rocks to shatter

32
Q

describe sediment transport?

A
  • beach drift and longshore current are the results of waves approaching coasts at an angle, together they form longshore drift
  • when waves approaching coast break at an angle to beach the beach, sediment move up the beach at angle as swash and perpendicularly down as backwash
  • the resulting zigzag movement is breach drift
  • when wave approach coast an angle, they create longshore current in nearshore zone and move sediment along shore. Longshore currents are ocean currents that flow parallel to coast
  • the combined effect is known as longshore drift
33
Q

what is sedimental deposition?

A
  • when the sea loses energy, it drops its load of sand, rock particles and pebbles, that is has been carrrying
    deposition happens when the swash is stronger than the backwash
  • deposition is likely to occur when
    waves enter an area of shallow water
    waves enter a sheltered area
    there is little wind
34
Q

how does cliff and shore platforms form?

A
  • a cliff is a near-vertical and steep rock face found along coasts
  • hydraulic action and abrasion may erode a crack or joint on rock surface, gradually enlarging crack or joint to form notch
  • notch may be further deepened to produce bigger hollow space called cave
  • as process of erosion continues, overhanging cliff is formed, eventually collapse and materials deposit at foot of cliff
  • some material may be carried by waves and throw against base of cliff, causing further erosion
  • over time cliff retreat inland and gently sloping platform appears at base of where cliff used to be
  • platform is called short platform, which is submerged during high tide
35
Q

how do headlands and bays form?

A
  • some coastlines have alternating bands of more resistant and less resistant rocks (like granite vs chalk)
  • less resistant rocks will be eroded away form bays, wide indented coasts
  • more resistant rocks extend out into sea as headlands.
  • result in indented coastline
36
Q

how do cave, arches, stacks and stumps form?

A
  • wave attack lines of weakness at base of headland (e.g. crack, joint, or fault) and undercut it. Action forms a cave at area that is hollowed by wave action
  • hydraulic action and abrasion may erode a crack or joint to form notch.
  • notch may be further deepened to produce bigger hollow space called cave
  • cave develop on each side of headland, further erosion may eventually join them together, leaving a brdige of rock known as arch above the opening
  • after further erosion, roof of arch may collapse to form stack, which is a pillar of rock left in sea after an arch collapse
  • if stack collapses further, a stump is formed
37
Q

how do depositional coasts form?

A
  • beach is zone of sediment deposition
  • beach materials may come from eroded cliffs, river deposits or sediment present in waves
  • slop of beach determined by grain size

Secondary 3 Geography (8 decks)

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