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Physical Geography- Coasts > The coastal system > Flashcards

The coastal system Flashcards

1
Q

what is negative feedback?

A

It’s when a change in the system causes other changes that have the opposite effect eg. as a beach is eroded the cliff behind it gets exposed to wave attack, the sediment eroded from the cliff is deposited on the beach causing it to grow in size again

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2
Q

what is positive feedback?

A

It’s when change in the system causes other changes that have a similar effect eg as a beach forms it slows down waves which can cause sediment to be deposited, increasing the size of the beach

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3
Q

what are the sources of energy in the coastal system?

A

wind, waves, tides and currents

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4
Q

how does wind create energy in the coastal system?

A
  • winds are created by air moving from high to low pressure
  • during storms the pressure gradient is high and winds can be strong
  • strong winds generate powerful waves, with strong prevailing winds creating higher-energy waves than winds that change direction
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5
Q

How do waves create energy in a coastal system?

A
  • waves are created by friction caused by wind giving it a circular motion
  • effect it has on the shore depends on the height which is affected by wind speed and fetch, high wind and long fetch create high and powerful waves
  • waves break at shore, with the friction of the sea bed slowing the bottom of the waves making their motion more elliptical
  • the stronger the swash and weaker the backwash means sediment is deposited
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6
Q

what is the fetch?

A

The distance that the wind has travelled across open water whilst creating waves

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7
Q

what are constructive waves?

A

A wave with a low frequency and are low and long, that deposits material up the beach after it breaks, deposits it, building up the beach. The swash is stronger than the backwash.

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8
Q

what are destructive waves?

A

High and steep waves with a high frequency, the backwash is stronger than the swash which erodes material from the beach

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9
Q

how do tides create energy on a coastline?

A
  • tides are caused by the gravitational pull of the moon and sun and are the periodic rise and fall of the ocean surface
  • tides affect where the wave breaks on the beach, with the area between high and low tide where most land forms are created and destroyed
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10
Q

how do currents supply energy to a coastline?

A
  • current can be caused by wind or variations in water temperature and salinity
  • currents move material along the coast
  • rip currents
  • upwelling- is the movement of cold water deep in the ocean to the surface, replacing the warmer water with nutrient rich currents
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11
Q

what are some inputs on the coast?

A
  • eg. sediment can be brought into the system in various ways, but energy inputs are wind, waves, tides and currents
  • geology
  • sea level change
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12
Q

what are some outputs on the coast?

A
  • eg. sediment can be washed out to sea, or deposited further along the coast
  • dissipation of wave energy
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13
Q

what are some transfers on the coast?

A

processes such as erosion, weathering, transportation and deposition

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14
Q

what are some stores on the coast?

A

land forms such as beaches, dunes and spits

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15
Q

What are high energy coasts?

A
  • They receive high energy inputs from large, powerful waves which are caused by strong winds, long fetches and steeply shelving offshore zones.
  • Steady prevailing winds
  • They tend to have sandy coves and rocky land forms such as cliffs or caves
  • higher rate of erosion than deposition
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16
Q

what are low energy coasts?

A
  • They receive low inputs of energy in the form of small, gentle waves
  • They can be caused by gentle winds, short fetches and gently sloping offshore zones
  • Some might have a reef or island offshore
  • They often have salt marshes and tidal mudflats
  • The rate of deposition is often higher than the rate of erosion
  • Typical landforms are beaches and spits
17
Q

Where are inputs of sediment brought to coastal systems from?

A
  • Rivers carry eroded sediment from inland
  • Sea levels rising can flood river valleys, forming estuaries
  • Eroded from cliffs
  • Waves, tides and currents can transport sediment into the coastal zone from offshore deposits
18
Q

What is the sediment budget?

A
  • The difference between the amount of sediment that enters the system and the amount that leaves
  • And requires identifying all sediment sources and sinks to calculate it
19
Q

What does a negative sediment budget lead to?

A

retreating coastline

20
Q

What are sediment cells?

A

Lengths of the coastline that are self contained for the movement of sediment, which means that processes going on in 1 cell doesn’t affect the movement of sediment in another- making it a closed system

21
Q

How many sediment cells are there in the UK?

A

11

22
Q

What type of equilibrium do coastal systems normally operate in, and what does it mean?

A
  • Dynamic equilibrium

- inputs and outputs are balanced

23
Q

What are the specific zones on the coastline/beach?

A
  • Backshore
  • Foreshore
  • Inshore
  • Offshore
  • Nearshore
24
Q

What is the backshore?

A
  • area between the high water mark and the landward limit of marine activity
  • Changes only normally take place here during storms
25
Q

What is the foreshore?

A
  • area between the high and low water marks

- Its the most important zone for marine processes in times that are not influenced by storms

26
Q

What is the inshore?

A

-area between the low water mark and where waves cease to have an influence on the land beneath them

27
Q

What is the offshore?

A

-area beyond the point where waves cease to impact the seabed and where activity is limited to deposition

28
Q

What is the nearshore?

A
  • area extending seaward from the high water mark to the area where waves begin to break
  • it includes;
  • swash zone-turbulent layer where waves break
  • surf zone-where waves break and where swash moves up the beach
  • breaker zone- where waves approaching the coastline begin to break with a water depth of around 5 to 10m
29
Q

What is wave refraction?

A
  • when waves approach an irregular shape coastline they are refracted and become increasingly parallel
  • the overall effect is that the wave energy becomes concentrated on the headland, causing greater erosion
  • with the lower energy waves spilling into the bay causing bay deposition
30
Q

what is the difference between neap and spring tides?

A
  • spring tides are the highest monthly tidal range produced when the moon, sun and Earth are in a straight line
  • Whereas neap tides are the lowest monthly tidal range, produced when the sun and moon are 90 degrees to each other in relation to the earth
31
Q

What are tidal surges?

A

Meteorological conditions give rise to strong winds which produce higher water levels than those at high tide

Physical Geography- Coasts (1 decks)

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