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A Level Physical Geography > Coasts- Sources of Energy > Flashcards

Flashcards in Coasts- Sources of Energy Deck (20)
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1
Q

Role of solar energy in the coastal system

A
  • initial energy input for the coastal system is from the Sun
  • Sun’s energy causes different air pressures (different rates of heating) which creates wind
  • this wind then generates waves
2
Q

How does wind strength impact wave energy?

A
  • the stronger the wind is, the bigger the wave created will be
  • because the energy in the wind will be transferred to the waves
3
Q

How does the fetch impact wave energy?

A
  • the greater the fetch, the bigger the wave will be

- the wind has more time to transfer its energy to the waves

4
Q

How does the duration of the wind impact wave energy?

A

-the longer time the wind has to transfer energy to the waves, the greater amount of energy the wave will have

5
Q

How are wind-driven waves formed?

A
  • created by the frictional drag between the wind and surface water
  • as wind blows across the surface of the ocean, the continual disturbance creates a wave crest
  • as the wave approaches the shore, disturbance to the circular motion beneath the surface leads to more horizontal wave movement
  • this causes the wave to break
6
Q

Why are some areas of the UK subjected to more powerful waves than others?

A
  • some areas have a much larger fetch
  • eg. The SW coast has a fetch extending 3000 miles across the Atlantic Ocean to Brazil
  • the large fetch gives the wind more time to transfer energy- making it more powerful
  • SE has a much smaller fetch- so less powerful waves
7
Q

Constructive wave characteristics

A
  • distant weather systems generate these in open ocean
  • low, surging waves
  • long wavelength
  • strong swash, weak backwash
  • beach gain (constructive)
  • associated with gentle beach profile
8
Q

Destructive wave characteristics

A
  • local storms responsible for these waves
  • high, plunging waves
  • short wavelength
  • weak swash, strong backwash
  • beach loss (destructive)
  • associated with steeper beach profile
9
Q

What are tides?

A

The periodic rise and fall in the sea level caused by the gravitational pull of the Sun and the moon (mainly the moon)

10
Q

Neap tide

A
  • moon at right angles to the Sun when in first or last quarter
  • gravitational pulls act against each other to create lower high tides and higher low tides
  • so there is a small tidal range
11
Q

Spring tides

A
  • Sun and moon in line at full moon or new moon
  • gravitational pulls act together to create higher high tides and lower low tides
  • so tidal range is large
12
Q

Characteristics of a high energy coastline

A
  • rocky coastline
  • erosion exceeds deposition
  • contains cliffs and headlands
  • in the UK- often Atlantic facing
  • many examples in Cornwall
13
Q

Characteristics of a low energy coastline

A
  • see less powerful waves
  • beaches and spits found
  • Sandy and estuarine coasts
  • deposition exceeds erosion
  • sheltered areas (eg. bays)
14
Q

Wave refraction

A
  • shape of sea bed reorients approaching waves- waves reach shallower water at different times
  • as water depth decreases, wave velocity decreases
  • waves are bent towards the part of the shoreline where they are moving most slowly
  • wave crests roughly mirror the contours of the sea bed
  • higher the sea bed relief, the slower the wave
  • wave height increases as they approach the shore
  • waves break and converge on headlands-increasing the energy released by breaking wave
15
Q

Rip currents

A
  • strong localised underwater currents that occur on some beaches
  • commonly formed when a series of plunging waves cause a temporary build up of water at the top of the beach
  • met with resistance from breaking waves- water returning down the beach is forced just below the surface (following troughs in beach profile)
  • this fast flowing offshore surge of water can drag people into deep water
16
Q

Tidal current

A

The horizontal movement of water accompanying the rising and falling of the tide

17
Q

Food current

A

The incoming tide along the coast and into bays/estuaries

-strongest occur before or near the time of the high and low tides (when water is closest to its highest/lowest values)

18
Q

Slack tides

A

The weakest currents which occur between the flood and ebb currents

19
Q

Ebb current

A

Outgoing tide

-strongest occur before or near the time of the high and low tides (when water is closest to its highest/lowest values)

20
Q

How do the impacts of large and small tidal ranges differ?

A
  • large tidal ranges useful for transporting sediment and providing energy for tidal currents
  • rip tides associated with large tidal ranges
  • smaller tidal ranges are important for concentrated erosion at the cliff face- may lead to wave cut platforms forming