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GEOGRAPHY - coasts > 1.B - influences on the coastal landscape > Flashcards

1.B - influences on the coastal landscape Flashcards

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1
Q

how does wind influence the coastline?

A

The wind is able to shape the coastline in 2 ways:
1. frictional drag that is has on the surface of the ocean is able to create waves which are capable of carrying out coastal marine erosion, transport and deposition.
- the wind direction will have a strong influence on wave direction and wind strength should have an effect on wave height.
2. - the wind itself is able to carry out erosion, transportation and deposition.
- these processes combine to create aeolian landforms, such as coastal dunes.

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2
Q

what is the WAVE LENGTH?

A

the distance from crest to crest

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3
Q

what is the wave crest?

A

the highest point of the wave

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4
Q

what is the wave trough?

A

the lowest point of the wave

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5
Q

what is the wave height?

A

the vertical distance from trough to crest

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6
Q

what is swash?

A

the movement of water up a beach after a wave has broken

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7
Q

what is backwash?

A

the flow of water down a beach after a wave has broken

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8
Q

what is a SPILLING BREAKER WAVE?

A
  • they occur as waves travel across a gently sloping bottom (i.e. near the beach).
  • the wave breaks long and slow, losing its energy as white water spilling from the crest down the front of the wave.
  • water spills gently forward as the wave breaks
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9
Q

what is a PLUNGING BREAKER WAVE?

A
  • occur as waves approach moderate to steep sea bottoms.
  • the wave becomes steeper than a spilling breaker
  • the crest falls as a well defined curve, falling forward with considerable energy
  • strong backwash, making them more destructive
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10
Q

what is a SURGING BREAKER WAVE?

A
  • low angle waves breaking onto steep beaches
  • the wave slides forward and may not actually break
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11
Q

what is fetch?

A

the distance of open water in 1 direction from a coastline, over which the wind can blow.

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12
Q

how are waves created?

A
  • waves are created by the wind blowing over the surface of the water,
  • out to sea this creates OSCILLATION WAVES which will have no forward momentum of water, only energy is transferred forward,
  • the wave height depends on the strength and duration of the wind, the depth of the water and the length of the fetch
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13
Q

what does wave height depend on?

A

the wave height depends on:
- the strength and duration of the wind
- the depth of the water and
- the length of the fetch

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14
Q

what is a swell wave?

A
  • this is the name for the waves generated out at sea.
  • they have long wavelength and a wave period of up to 20 secs
  • this contrasts against locally produced storm waves, which have a greater wave height, shorter wavelength and wave period.
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15
Q

what are the characteristics of a CONSTRUCTIVE WAVE?

A
  • low in height
  • long wavelength
  • low frequency (typically 6-8 per min)
  • break as spilling waves and strong swash travels a long way up the gently sloping beach
  • due to long wavelength, backwash returns to the sea before the next wave breaks, so the next swash movement is UNINTERRUPTED, and thus retains its energy
  • a key feature is that (therefore) swash energy exceeds backwash energy.
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16
Q

what are the characteristics of a DESTRUCTIVE WAVE?

A
  • greater height
  • shorter wavelength
  • higher frequency (12-14 per min)
  • break as plunging waves so there is little forward transfer of energy to move water up the steeply sloping beach as swash.
  • friction from the steep beach slows the swash so it doesn’t travel far before returning down the beach as backwash
  • with a short wavelength, the swash of the next wave is often slowed by the frictional effects of meeting the returning backwash of the previous wave
  • swash energy is LESS that backwash energy.
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17
Q

what are aeolian processes?

A

any landform shaped by WIND

18
Q

what is wind’s effect on the coastal landscape?

A
  • the source of energy for coastal erosion and sediment transport is wave action.
  • this wave energy is produced through the frictional drag of wind across the oceans surface.
  • THE HIGHER THE WINDSPEED AND THE LONGER THE FETCH, THE LARGER THE WAVES AND THE MORE ENERGY THEY POSSESS.
19
Q

how does the direction of wind influence the coastline?

A
  • onshore winds, blowing from the sea towards the land, are particularly effective at driving waves towards the coast.
  • if wind blows at an oblique angle to the coast, the resultant waves will also approach obliquely and generate long shore drift.
20
Q

what is wind?

A
  • wind is a moving force and as such is able to carry out erosion, transportation and deposition itself.
  • these aeolian processes contribute to the shaping of many coastal landscapes.
21
Q

what is the significance of wind energy?

A
  • overall not very significant
  • wind could be considered significant as it is responsible for the strength, severity and direction of waves.
  • wind causes friction on the sea surface causing waves; the greater the fetch the bigger the waves.
  • the significance of wind CHANGES FROM DAY TO DAY MAKING IT A TEMPORAL FACTOR.
22
Q

how do aeolian processes and the succession of plants work together to create dune complexes?

A
  • at low tide, incoming solar radiation (input of energy) is able to dry the sand out.
  • as the wind blows over the sand it is able to erode it by processes of deflation (erosion of clay and silt-sized particles by wind action in dry lands).
  • dry sand is much easier for wind to pick up than wet sand, as moisture increases cohesion between particles to help them stick together.
  • plant roots help to build up and stabilise sand (e.g. prickly saltwort.)
  • pioneer plant species are zerefite (well adapted)
  • e.g. they don’t lose water as easily by transpiration due to waxy leaves / deep roots to access nutrients.
  • plants act as a shield.
23
Q

what is a concordant coastline?

A

a coastline with bands of different geologies lying PARALLEL to the shore.

24
Q

what is a discordant coastline?

A
  • rock strata lies at right angles to the coast.
  • deep bays and pronounced headlands produced.
  • more resistant rocks form headlands, weaker rocks form bays.
25
Q

what is the angle of dip?

A

the angle of the strata (layers) in sedimentary rocks when compared to the horizontal.

26
Q

what types of current are there?

A
  • currents can either be local currents such as rip currents or tidal currents
  • or much larger ocean currents such as the North Atlantic Drift
27
Q

what are ocean currents?

A

large scale phenomena that are generated by convection from the Earth’s rotation

28
Q

how do rip currents form?

A
  • caused by tidal motion or by waves breaking at right angles to the shore.
  • water from the top of breaking waves with a large height travels further up the shore and then returns through the adjacent area where the lower height waves have broken.
29
Q

what impact do rip currents have on coastlines?

A
  • once rip currents have formed, they modify the shore profiles
  • by creating cusps
  • which help perpetuate the rip current, channelling flow through a narrow neck.
30
Q

how do warm and cold ocean currents alter UK coastlines?

A
  • warm ocean currents transfer heat energy from low latitudes towards the poles.
  • they change the temperature of water, (alters the amount of freeze-thaw weathering), which affects weathering processes and input of sediment to a system.
  • cold currents do the opposite (towards the equator) which therefore results in less effect on our coastlines.
31
Q

what causes tides?

A
  • The moon pulls the water towards itself, creating a HIGH TIDE, and there is a compensatory bulge on the other side of the earth.
  • At locations between the two bulges, there will be a LOW TIDE.
  • As the moon orbits the earth, the high tides follow it.
  • The highest tides will occur when the moon, sun and earth are all aligned and so the gravitational pull is at its strongest.
  • On a more local level, tides are controlled by the geomorphology of the sea bed and shape of the coastline.
32
Q

what are tides?

A
  • the periodic rise and fall of the sea’s surface
  • that are caused by the gravitational pull of the moon and (to a lesser extent) the sun
33
Q

what is tidal range?

A

the vertical difference in height between consecutive high and low waters over a tidal cycle.

34
Q

what influence do tides have on the coastline?

A
  • Tides determine the position at which the waves break on the beach, but also the range over which wave action can occur.
  • In enclosed seas, such as the Mediterranean, tidal ranges are low and so wave action is restricted to a narrow area of land.
  • In places where the coast is funnelled, such as the Severn Estuary, tidal range can be as high as 14m.
  • The tidal range, therefore, influences where wave action and coastal processes can occur.
  • A small tidal range leads to erosional processes dominating.
  • A large tidal range leads to depositional processes dominating.
35
Q

what are spring tides?

A
  • The highest tides will occur when the moon, sun and earth are all aligned and so the gravitational pull is at its strongest.
  • This happens twice each lunar month and results in SPRING TIDES with a high tidal range.
36
Q

what are neap tides?

A

twice a month, the moon and the sun are at right angles to each other and the gravitational pull is therefore weakest, producing NEAP TIDES with a low range

37
Q

what are tides controlled by on a local level?

A

tides are controlled by the geomorphology of the sea bed and shape of the coastline.

38
Q

why does the tidal range vary across the planet?

A
  • shape of coastlines change
  • oceans are able to have a bigger difference
39
Q

how will having a large tidal range affect coastal processes/landforms?

A
  • large tidal ranges results in more deposition
  • tidal range influences where wave action occurs, the weathering processes that happen on land exposed between tides and the potential scouring effect along coasts with a high tidal range.
  • deposition is dominant and creates a greater number of estuaries
40
Q

how will having a small tidal range affect coastal processes/landforms?

A
  • smaller tidal ranges result in more erosion due to the fact the waves are hammering a smaller area more often and with more force
  • wave energy is concentrated in a smaller area
41
Q

what does tidal range influence?

A

the level of weathering

GEOGRAPHY - coasts (9 decks)

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