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Geography > Coastal landscapes, processes and change - Coast landforms and landscapes > Flashcards

Coastal landscapes, processes and change - Coast landforms and landscapes Flashcards

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1
Q

What are waves caused by?

A

Waves are caused by friction between wind and water.

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2
Q

Why are waves extremely important along any stretch of the coast?

A

They are extremely important along any stretch of the coast as they directly influence the three marine processes of erosion, transport and deposition.

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3
Q

What factors does wave size and strength depend on?

A

Wave size and strength depends on:

  • the strength of the wind
  • the length of time the wind blows for
  • water depth
  • wave fetch
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4
Q

What is the fetch?

A

The uninterrupted distance across water over which the wind blows. It is the distance over which waves are able to grow in size.

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5
Q

What is the difference between waves and tides?

A

Tides are formed by the gravitational pull of the Moon on water on the Earth’s surface. This causes sea level (the tide) to rise and fall twice a day. Tidal ranges vary from place to place. Waves are more localised disturbances of the sea caused mainly by wind.

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6
Q

What is happening to the water particles within a wave?

A

They are moving in a circular rotation.

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7
Q

What are the characteristics of constructive waves?

A

Constructive waves are of low height and long length. They are sometimes described as ‘spilling’ waves with a strong swash and a weak backwash. The strong swash pushes sediment up the beach and deposits it in a ridge at the top of the beach. The weak backwash means that the deposited material is not dragged back to the sea.

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8
Q

What is swash?

A

The flow of seawater up a beach as a wave breaks.

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9
Q

What is backwash?

A

The return flow of seawater back down the beach to meet the next incoming wave.

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10
Q

What are the characteristics of destructive waves?

A

Destructive waves are relatively high with a short length. This makes them ‘plunging’ waves with a strong backwash that erodes and carries away beach material.

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11
Q

What is beach morphology?

A

The shape of a beach, including its width and slope (the beach profile) and features such as berms, ridges and runnels. It also includes the type of sediment (shingle, sand, mud) forming the beach.

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12
Q

What is beach morphology strongly conditioned by?

A

Beach morphology is strongly conditioned by the nature of the prevailing waves. But wave conditions can fluctuate over time and bring with them changes to beach morphology.

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13
Q

What are the four diagnostic beach features of prevailing wave conditions?

A

There are four diagnostic beach features of prevailing wave conditions:

  • storm beach: the result of constructive waves during stormy weather
  • berms: small ridges built by constructive waves during relatively calm weather
  • cusps: the product of gentle destructive waves eroding berms
  • offshore bars: formed by persistent destructive waves.
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14
Q

What is a storm beach the result of?

A

The result of constructive waves during stormy weather

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15
Q

What are berms?

A

Small ridges built by constructive waves during relatively calm weather

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16
Q

What are cusps?

A

The product of gentle destructive waves eroding berms

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17
Q

What are offshore bars formed by?

A

Formed by persistent destructive waves.

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18
Q

Identify the sources of beach material.

A

From the erosion of the coast from silt and sand brought down the coast by rivers. Some may also come directly from weathering and mass movement. Material can also be rolled towards the coast from offshore deposits.

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19
Q

When does erosion mostly occur?

A

It mostly occurs during storms when:

  • waves approach the coast at rights angles
  • the tide is high
  • heavy rainfall has weakened the rocks of the cliff
  • debris at the foot of the cliff has been removed and no longer protects this critical point.
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20
Q

Why does most erosion take place during storms?

A

That is when wave energy is at its strongest and waves strike the coast with great force. Wave activity at this time will predominantly destructive rather than constructive.

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21
Q

What are the four main types of marine erosion?

A

There are four main types of marine erosion:

  • hydraulic action
  • abrasion (corrasion)
  • attrition
  • corrosion (solution).
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22
Q

What is hydraulic action?

A

Wave quarrying when air trapped in joints and cracks is compressed by the force of waves crashing against the cliff

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23
Q

What is abrasion (corrasion)?

A

Sediment being carried in the waves has a wearing-down effect

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24
Q

What is attrition?

A

The wearing down of sediment as it is moved around by the waves

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25
Q

What is corrosion (solution)?

A

Carbonate rocks such as limestone are dissolved by rainwater, sea spray and seawater.

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26
Q

How is a wave-cut notch formed?

A

Perhaps the most critical erosional feature is the wave-cut notch formed by the process of hydraulic action and abrasion. As the notch becomes deeper, the rocks overhanging it become unstable and eventually collapse. Repeated cycles of notch cutting and collapse cause cliffs to recede inland.

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27
Q

What happens to the wave-cut notch as it becomes deeper?

A

As the notch becomes deeper, the rocks overhanging it become unstable and eventually collapse. Repeated cycles of notch cutting and collapse cause cliffs to recede inland.

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28
Q

Explain the sequence of erosional landforms that starts with a cave and finishes with a stack.

A

The cave is subjected to erosion, particularly hydraulic action. The cave is gradually enlarged until it reaches a cave being excavated on the other side of the headland. When they join, an arch is formed. This is gradually weakened until the point is reached when the cave roof collapses and the outer-limb of the each becomes a stack.

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29
Q

What are the four different ways sediment is transported by the sea?

A

Sediment is transported by the sea in four different ways:

  • traction
  • saltation
  • suspension
  • solution.
30
Q

What is traction?

A

Heavier sediment (pebbles, boulders) rolls along the sea floor, pushed by waves and currents

31
Q

What are currents?

A

Flows of seawater in a particular direction driven by wind, tides and differences in density, salinity and temperature.

32
Q

What is saltation?

A

Sediment (mainly sand particles) bounces along the floor

33
Q

What is suspension?

A

Fine sediment (slit, clay) is carried within the body of water

34
Q

What is solution?

A

Dissolved sediment (calcium carbonate) is carried in the water as a solution.

35
Q

What is longshore drift?

A

Much of the transport of sediment takes place along the coast rather than into and away from the shore. This is known as longshore drift. Such movement is produced by waves approaching the coast at an angle. The swash pushes sediment obliquely up the beach and backwash returns it directly to the sea. The combination results in sediment slowly moving along the coast in the same general direction as the waves approach the shore.

36
Q

What is longshore drift produced by?

A

Such a movement is produced by waves approaching the coast at an angle.

37
Q

What does the combination of the swash and backwash in longshore drift result in?

A

The combination results in sediment slowly moving along the coast in the same general direction as the waves approach the shore.

38
Q

Is longshore drift a current? Give your reasons.

A

Yes, because it flows consistently in a given direction. But unlike ocean currents, it is not driven by differences in water salinity and temperature. It provides a means of transporting sediment along the coast.

39
Q

What are the main features produced by the deposition of transported sediment?

A

The main features by the deposition of transported sediment are:

  • bayhead beach
  • spit
  • recurved hooked spit
  • bar
  • tombolo
  • cuspate foreland.
40
Q

What is a bayhead beach?

A

An accumulation of sand at the head of a sheltered stretch of water between two headlands

41
Q

What is a spit?

A

A sand or shingle beach ridge extending beyond a turn in the coastline

42
Q

What is a recurved hooked spit?

A

A spit built out into a bay or across an estuary, the end of which curves landward into shallow water

43
Q

What is a bar?

A

A sand or shingle beach extending across a coastal indentation with a lagoon behind

44
Q

What is a tombolo?

A

A sand or shingle bar that attaches a former offshore island to the coast

45
Q

What is a cuspate foreland?

A

A triangular area of shingle extending out from a shoreline, possibly formed by longshore drifts from opposing directions.

46
Q

What are sediment cells?

A

Long stretches of coastline that operate as almost self-contained physical systems. In each sediment cell there are sources (inputs), where sediment is generated (e.g. eroding cliffs and beaches), transfer zones (flows), which are stretches where sediment is moving along the coast by longshore drift and currents, and sinks (outputs), locations where the dominant process is deposition (e.g. spits and offshore bars).

47
Q

What is weathering?

A

The disintegration and decomposition of rocks in situ by the combined actions of the weather, plants and animals.

48
Q

What is mass movement?

A

A collective term for the processes responsible for the downslope movement of weathered material under the influence of gravity.

49
Q

What is the difference between weathering and mass movement?

A

Weathering does not involve any form of movement whereas erosion does. This is due to the action of external forces, such as wind and running water.

50
Q

What are the three types of weathering?

A

There are three types of weathering:

  • mechanical
  • chemical
  • biological.
51
Q

What is mechanical weathering?

A

The breakdown of rock by some form of physical force

52
Q

What is chemical weathering?

A

Involving a chemical reaction and decomposition

53
Q

What is biological weathering?

A

The actions of bacteria, plants and animals, which speed up mechanical and physical weathering

54
Q

What are the processes of weathering in any location conditioned by?

A

The process of weathering at work in any location are conditioned by the climate (rather than weather). Temperature and precipitation are the key climatic elements.

55
Q

What type of weathering prevails in the hot, humid parts of the world?

A

Strong chemical weathering

56
Q

Where in the world is mechanical weathering most effective, and why?

A

In cold, temperate or periglacial regions, where there is little precipitation but temperatures fluctuate around freezing point. Much freeze-thaw activity causes much mechanical weathering.

57
Q

What can mass movement be classified according to?

A

Mass movement can be classified in a number of ways, such as by the speed of movement and the type of material moving (solid rock, debris or soil).

58
Q

What are the common types of mass movement along cliffed coastlines?

A
  • Rockfalls occur where the rock on a cliff being undercut by the sea is weakened by weathering. Falls can be sudden and spectacular.
  • Rotational slides are slow downslope movements of a mass of rock or debris over a curved plane. They are particularly common where a permeable (e.g. sandstone) overlies an unstable impermeable rock (e.g. clay). Water passing through the permeable rock lubricates the junction with the underlying impermeable rock, thus facilitating the sliding.
  • Landslides are sudden downslope surges occurring when weathered rock and soil become saturated and lubricated by water (meltwater, springs).
59
Q

When do rockfalls occur?

A

Rockfalls occur where the rock on a cliff being undercut by the sea is weakened by weathering. Falls can be sudden and spectacular.

60
Q

What are rotational slides and when are they particularly common?

A

Rotational slides are slow downslope movements of a mass of rock or debris over a curved plane. They are particularly common where a permeable rock (e.g. sandstone) overlies an unstable impermeable rock (e.g. clay).

61
Q

When are rotational slides particularly common?

A

They are particularly common where a permeable rock (e.g. sandstone) overlies an unstable impermeable rock (e.g. clay).

62
Q

What happens as water passes through an impermeable rock?

A

Water passing through the permeable rock lubricates the junction with the underlying impermeable rock, thus facilitating the sliding.

63
Q

What are landslides and when do they occur?

A

Landslides are sudden downslope surges occurring when weathered rock and soil become saturated and lubricated by water (meltwater springs).

64
Q

What are the distinctive coastal landforms created by mass movement?

A

The distinctive coastal landforms created by mass movement include screes (the product of mechanical weathering of an exposed rock face), rotational scars (the outcome of slumping) and cliff terraces (the result of rotational sliding).

65
Q

What is the difference between a) rockfalls and rotational slides, b) screes and cliff terraces?

A

a) Rockfalls are a rapid form of mass movement (rocks often falling vertically) whereas rotational slides are the outcome of mass movement along curved failure surfaces.
b) Screes are masses of weathered, angular rock fragments collecting below a free face to create a talus. Cliff terraces are the result of rotational sliding.

66
Q

Why do sea levels change on a day-to-day basis?

A

Sea levels change on a day-to-day basis as a result of tides, changes in atmospheric air pressure and winds. Such changes are very short term.

67
Q

Why do sea levels change over long time scales?

A

Over long time scales, sea-level changes are more permanent and the outcome of complex factors. Part of the complexity is that a change in sea level can be brought about by a change either in land level (isostatic change) or in the volume of the sea (eustatic change).

68
Q

What does a marine regression result from?

A

A marine regression results from a eustatic fall in sea level (as during glacial periods when water becomes locked up in ice and snow) and an isostatic fall in sea level (when ice sheets melt and the land rises). Both movements expose the seabed and produce an emergent coast.

69
Q

What type of coast is produced from marine regression?

A

Both movements expose the seabed and produce an emergent coast.

70
Q

What does a marine transgression result from?

A

A marine transgression results both from a eustatic rise in sea level (at the end of a glacial period) and an isostatic rise in sea level (when land sinks under the weight of accumulated snow and ice). In both cases, large areas of land are submerged beneath the sea, producing a submergent coast. The ria coastline is one of the best examples of such a coast.

71
Q

What type of coast is produced from marine transgression?

A

Large areas of land are submerged beneath the sea, producing a submergent coast. The ria coastline is one of the best examples of such a coast.

Geography (25 decks)

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