Coasts Flashcards

1
Q

Define Fetch

A

The distance the wind is blowing over water creating waves. Bigger fetch = bigger waves

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2
Q

What are the two different types of waves and how do they differ?

A

Destructive:
* Erosion - takes away coastline
* Large waves AKA plunging waves -> they plunge onto shore
* Backwash stronger than swash
Constructive:
* Deposition - builds features
* Small waves AKA spilling waves -> they spill onto shore
* Backwash is weaker than swash

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3
Q

How many constructive waves are there per minute?

A

6-8

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4
Q

How many destructive waves are there per minute?

A

10-14

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5
Q

What shape are constructive waves?

A

Flat

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6
Q

What shape are destructive waves?

A

Plunging

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7
Q

What season are constructive waves most prevalent?

A

Summer

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8
Q

What season are destructive waves most prevalent?

A

Winter/spring

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9
Q

Define swash

A

Water coming up onto beach/coast after the wave breaks

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10
Q

Define backwash

A

Water retreating back down the beach after a wave has broken 2

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11
Q

How many high and low tides are there daily?

A

Two high tides and two low tides

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12
Q

Name some erosional features of coastlines

A
  • Bay and headland
  • Cliff
  • Wave cut platform
  • Cave
  • Sea Arch
  • Sea Stack
  • Sea stump
  • Blowhole
  • Geo
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13
Q

Name some depositional features of coastlines

A
  • Beach
  • Sandspit
  • Sand bar
  • Tombolo
  • Lagoon
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14
Q

Define prevailing wind

A

The wind that occurs most frequently in an area

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15
Q

What is the fetch like on the west coast of Ireland and why?

A

It is large forming very powerful waves. This is because there is 5000km of open sea between the west coast and the USA

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16
Q

What is the prevailing wind in Ireland?

A

South west

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17
Q

What is the fetch on the east coast of Ireland like and why?

A

It is small so waves don’t have the same power because there is only 100km of open sea to Wales.

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18
Q

Define wave frequency

A

The number of waves passing a given point per second. High wave frequency means more energy delivered to coastline

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19
Q

Explain wave refraction

A

The bending of waves as they approach a coastline at an angle. This occurs because waves slow down in shallower water, causing them to align more parallel to the shore.

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20
Q

Define tide

A

The periodic rise and fall of sea levels due to the gravitational pull of the moon and sun

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21
Q

Define constructive waves

A

Low energy waves that deposit material onto the shore forming beaches. Strong swash and weak backwash

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22
Q

Define destructive waves

A

High energy waves that erode the coastline. They have a weak swash and strong backwash, removing material from the shore.

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23
Q

Define longshore drift

A

The movement of sediment along the coast due to waves hitting the shore at an angle

24
Q

Define coastal erosion

A

The wearing away of land by natural forces such as waves, wind and rain

25
Q

Draw a diagram to show constructive waves

26
Q

Draw a diagram to show destructive waves

27
Q

Name and explain some factors affecting coastal erosion

A
  • Wave Energy: Destructive waves erode coasts because they are larger so have more energy
  • Fetch: The longer a wave travels the more powerful it is
  • Rock Type: Hard rock eg. Granite is more resistant to the erosive power of waves. Unconsolidated material such as silt/clay erodes much faster.
  • Coastal Slope: Steep coastlines are more susceptible to erosion
  • Tides and currents: Strong tidal currents erode coastlines by moving sediment along coasts
  • Weather and climate: Storms erode coasts more. Global warming leads to rising sea levels which affects coastal erosio
  • Vegetation: Vegetation eg. Maram grass stabilises the sand and makes erosion harder
28
Q

Draw diagram to show the different processes of coastal erosion

29
Q

Define hydraulic action in the context of coastal erosion

A

Power of the waves crashing against the coastline

30
Q

Define abrasion in the context of coastal erosion

A

The sea using its load to erode the coastline

31
Q

Define attrition in the context of coastal erosion

A

Eroded material collides against itself and waves causing friction

32
Q

Define compression in the context of coastal erosion

A

Air is compressed in cracks and joints when waves hit. When they, retreat, the air expands causing an explosive effect

33
Q

Define solution in the context of coastal erosion

A

Dissolving rock by salts in seawater

34
Q

Example of Cliffs in Ireland

A

Cliffs of Moher, Co. Clare

35
Q

What erosional processes form sea cliffs and wave cut platforms?

A

Hydraulic action, abrasion, attrition and compression

36
Q

Define coastal transportation

A

Material eroded by waves and broken down further by attrition becomes light enough to be transported by sea currents

37
Q

Draw a diagram to show longshore drift

38
Q

Explain longshore drift

A
  • Friction causes waves approaching shore to break
  • This causes swash to carry pebbles and other material up the beach
  • Water then flows back out to sea, carrying some materials with it
  • Sometimes wind direction causes swash to push sediment along beach at an angle
  • The backwash then flows back to sea at 90 degree angle
  • This process causes deposited sediment to be moved along shoreline
39
Q

Give an Irish example of a tombolo

A

Howth, Co. Dublin

40
Q

Draw a diagram to show features of coastal deposition

41
Q

What type of waves form a beach?

A

Constructive

42
Q

Where is a beach found

A

Between the low tide and high tide marks

43
Q

Give an Irish example of a beach

A

Salthill Beach, Galway

44
Q

Name the different types of beaches

A
  • Storm beach
  • Pocket beach
  • Sand beach
  • Shingle beach
  • Coral beach
45
Q

What is a storm beach made up of?

A

Pebbles and stones

46
Q

Where are pocket beaches found?

A

In sheltered bays

47
Q

How do beaches form?

A
  • Waves carry material up the beach (swash)
  • The waves loses energy and deposits material on the shore
  • Constructive waves have a weak backwash and do not carry material away
  • The weak backwash with no energy to drag material back out to sea sorts material
  • Larger materials are at backshore, finer materials are at foreshore
48
Q

Define backshore

A

Steeper upper beach that contains coarse material such as angular rocks and shingle

49
Q

Define foreshore

A

Gentle lower beach that contions fine material such as sand and mud

50
Q

Name and explain some features found at beaches

A
  • Cusps: Crescent shaped hollows
  • Berms: Terraces on beach
  • Ridges and runnels: Sandy mounds (ridges) parallel to the shore
51
Q

Draw a diagram to show a beach and its features

52
Q

Name and explain some hard engineering solutions to coastal defence with examples

A
  • Sea Walls: Tall concrete walls designed to absorb and reflect wave energy. Eg. Promenade, Galway City costing €12 million
  • Rock Armour (Riprap): Large boulders placed at the base of cliffs or dunes to break wave energy. Eg. Doolin, Co. Clare and Co. Wexford costing ~€1000 per metre of shoreline
  • Gabions: Wire cages filled with rocks placed to support soft cliffs or protect roads. Eg. Villages in Donegal
  • Groynes: Wooden or stone barriers built perpendicular to the shore to trap sand and slow longshore drift. Eg. Dublin Bay and Wicklow
53
Q

Name and explain some soft engineering solutions to coastal defence with examples

A
  • Beach nourishment: Sand is added to eroding beaches to build them up. Eg. Portraine, North Co. Dublin in 2020 to protect houses costing €500,000
  • Managed retreat: Allowing certain areas to flood or erode naturally while protecting key assets elsewhere. Eg. Shannon Estuary
54
Q

What is the difference between hard and soft engineering solutions to coastal defence?

A

Hard engineering: Building physical structures to protect coastline

Soft engineering: These aim to work with nature rather than against it

55
Q

Name some places in Ireland worst affected by coastal erosion

A
  • Portrane, Co. Dublin
  • Lahinch, Co. Clare
  • Clontarf and Dollymount, Co. Dublin
  • Rosslare, Co. Wexford
56
Q

Beaches (30m)