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Coastal environments Flashcards

1
Q

Different areas of a coast

A
  • upper beach/backshore = not covered by water, backed by cliffs or sand dunes
  • foreshore = periodically exposed by the tides
  • nearshore = breaker zone
  • offshore = permanently under water
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2
Q

Draw diagram of waves oscillation (circular orbit)

A

…

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3
Q

Wave length

A

Distance between two successive crests/troughs

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4
Q

Wave height/amplitude

A

Vertical distance between the through and the crest

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5
Q

What is wave height determined by?

A

Wind strength, fetch, depth of sea

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6
Q

Swell waves

A

Waves of up to 12-15m, can travel vast distances away from the generation are - low height, large wavelength

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7
Q

Storm waves

A

Characterised by smaller wavelength, larger wave height and greater frequency - created directly from a storm

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8
Q

Wave shoaling

A

Process by which waves approaching the shore slow down due to friction, causing the wavelength do decrease and wave height to increase

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9
Q

Spilling breakers

A

Gentle beach gradients and steep waves in terms of wave high relative to wave length
Gradual peaking of the wave until the crest becomes unstable, resulting in a gentle spilling forward of the crest.

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10
Q

Plunging breakers

A

Tend to occur on steeper beaches than spilling breaks, with wave of intermediate steepness
Distinguished by the ‘plunging’ action

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11
Q

Surging breakers

A

Steep beaches with low steepness waves

Front face and crest remain relatively smooth and the waves slide up the beach without directly breaking

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12
Q

Constructive waves (type of wave translations)

A
  • low wave frequency
  • waves generated far offshore
  • spilling breaker formed
  • strong swash, high lateral energy
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13
Q

Destructive waves (type of wave translations)

A
  • high wave frequency, resulting from locally generated wind
  • generally associated with steep coastline (coarse material like gravel)
  • resultant rapid increase in the friction forces the forward rotation of waves, creating a particularly strong backwash.
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14
Q

What are tides influenced by?

A
  • size and shape of ocean basins
  • characteristics of the shoreline
  • coreolis force
  • meteorological conditions
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15
Q

What happens to water levels during low pressure systems?

A

Water levels are raised by 10cm for every decrease of 10mb

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16
Q

3 types of tides and when do they occur

A
  1. Low spring tides after a new Moon
  2. High spring tides after a full Moon
  3. Neap tides occur when the Sun and Moon are at right-angles to the Earth
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17
Q

5 sources of sediment

A 
> reworked beach deposits
> off-shore marine deposits
> materials from mass movement
> wind-blown deposits
> artificial beach nourishments
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18
Q

Bedload (type of sediment transport)

A

Salation and traction

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19
Q

Suspended load

A

Suspension and solution - grains transported as wash loads are permanently in suspension and typically consists of clays and dissolved material.

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20
Q

Coastal sediment/littoral sediment system definition

A

A simplified model that examines coastal processes and patterns in a given area - in each cell, inputs and outputs are balanced

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21
Q

Dynamic equilibrium definition

A

Change to one of the inputs causes a knock-on effect on the processes and a resulting change in the landforms.

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22
Q

Draw the three types of shore platform

A

Sloping, sub-horizontal, plunging cliff

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23
Q

Explain the formation of a bevelled cliff

A

DIAGRAM

  1. Vertical cliff formed due to marine processes in the last interglacial period - sea levels higher than today
  2. During subsequent glacial phase, sea levels dropped - periglacial processes such a solifluction and freeze-thaw affected the former sea cliff,forming and angled slope
  3. When the sea levels rose again, renewed wave erosion removes debris and steepens the base of the cliff, leaving the upper part at a lower angle
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24
Q

Coastal platform formation (rather than wave cut platform)**

A

In high latitudes, first action could also be important in supporting wave activity
In other areas, solution weathering, salt crystallisation weathering and slaking could all support wave activity, particularly in the tidal and splash zones
Marine organisms, especially algae, can accelerate weathering at low-tide and in the area just above the high water mark - C02 from these organisms helps create acidic conditions
Other organisms may bore into rock surfaces

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25
Beach definition
Accumulation of material deposited between low water mark spring tides and the highest point reached b storm waves at high water mark spring tides
26
What can be find at the HWM
Berm or shingle ridge, as coarse material has been pushed up the beach by spring tides and aided by storm waves.
27
Beach cusps
* cusp diagram - self perpetuating because, swash is broken up by the cusp projection, concentrating energy onto the cusp - cusps develop best in areas of high tidal range where waves approach the coast at right-angles - spacing of cusps is related to wave height and swash strength
28
Features of the foreshore
1) Beach material may be undulating due to the creation of ridges called fulls - running parallel to the water line, pushed up by constructive waves at varying heights of the tide 2) These fulls are separated by throughs
29
Features of the offshore
The first material is deposited, waves touch the seabed and material is sometimes pushed up as offshore bars
30
Sand ripples
Movement of sand towards sea with the backwash
31
Draw beach profile
See sheet in revision folder/textbook
32
What happens when it is a spring tide
Tidal range is at its maximum
33
Storm beach
A very steep beach composed of wounded cobbles, shingle and occasionally sand
34
Swash-aligned coast
A coast that is aligned parallel to crests of prevailing waves
35
Drift-aligned coast
A coast aligned at an angle to crests of prevailing waves
36
Bars
- bars develop when a spit extends all the way across and inlet. - ridge of material joined at both ends to the mainland (above sea level) - a lagoon forms between the bar and the original coastline
37
Tombolo
-When the beach extends outwards to join an offshore island e.g. Chesil Beach, Dorset.
38
Cuspate tombolo
- Where two beaches extend to the same island due to wave refraction which causes longshore drift to operate in opposite directions either side of offshore islands where waves usually approach at right angles to the shore.
39
Spit
Extension of a beach into a sea -> longshore drift over time transports sediment into the sea where the direction of the coastline drastically changes. As the beach extends i not the water, its end may start to curve due the prevailing wind direction changing temporarily.
40
Compound spit
Exhibit a number of recurved spits along their length as each recurvature represents a break in coast orientation and the development of a new extension of the main spit under conditions of consistent LSD
41
Salt marsh definition
Vegetation that occurs on muddy shores between approximately mean high water neap and extreme high water spring tides, encouraging more deposition once formed.
42
Tidal creek
Where the tide flows and ebs
43
Flocculation
Sticking together of clay particles
44
Mudflat
A flat area of muddy land left uncovered at low tide
45
Halophyte
Vegetation tolerant of salty conditions
46
Halosere
A series of communities displaying a successional sequence where the plants are adapted to salt water => salt marsh succession
47
Salt marsh formation
1. The tidal currents are slowed so they begin to deposit material fine-grained material. A thin layer of mud from over sand which is covered at each tide. Algae on the mud help to consolidate the mud and trap more sediment 2. More mud is deposited, encouraged by the growth of eelgrass in submerged areas. Bioconstruction as currents slowed further and more silt is accumulated. Mud flats develop -> often intersected by creeks 3. As mud flats become higher, colonisation by pioneer plant species (halophyte) 4. Pioneer species develop close vegetation over the mud; allows colonisation by plants like marsh grass. Such plants develop in the sward zone 5. As mud levels rise, complex creek systems evolve that channel the retreating high tides. 6. Mud flats are increased in size by 1-30mm per year, as vegetation slows down tidal currents further and accumulates more particles 7. As it rises above land, new species like reeds become established, as well as trees like ash.
48
Psammosere
Plant succession starting on sand
49
Sand dune definition
Accumulations of sand grains, shaped into mounds or ridges by the wind under the influence of gravity
50
Succession
New plant species take hold and change their environment, allowing other species that are better suited to the new environment to succeed old species
51
Climax species
Heath and woodland in the mature dune
52
Zonation
Different dunes have specific characteristics
53
Strand line
Where the beach meets the foredune
54
Blow-out
Where the wind has blown away an area of the sand dune
55
3 conditions needed for sand dune formation
Sand, accommodation space, strong inland wind
56
Draw the process of sand dune formation
...
57
Embryo dune
Mainly sand and some marram grass, pH8
58
Fore dune
Marram grass and sea rocket, sand and plants
59
Yellow dune
More humus, pH7.5, vegetation dominated by marram grass
60
Grey dune
More sheltered, less acidic, dune heath, gorse
61
Dune slack
Water-loving plants: willow, moss etc.
62
Mature dune
Trees: birch, aider, oak
63
Characteristics of mangroves
Located in the inter-tidal zone, tall roots, can filter out salt water, need more than 24 degrees in the warmest month, rainfall exceeds 1250 mm, low latitudes, low wave energy. Buttress roots for extra stability. Can filter oxygen. Exhibit xerophytic adaptation (drought adapted)
64
Information about Sundarbans mangroves
By planting mangroves on delta sediments washed down from the Himalaya, it has gained over 300,000 acres of new land in the Bay of Bengal. Half a million Bangladeshis come into the Sundarbans each year to harvest its products
65
Eustatic
Refers to a global change in the sea level
66
Isostatic adjustments
The change in the level of the land relative to the level of the sea (tectonic activity or removal of an ice sheet)
67
Features of emerged coastlines include
Raised beaches Coastal plains Relict cliffs Raised mudflats
68
Features of submerged coastline include
Rias - drowned river valleys caused by rising sea levels Fjords - glacial troughs occupied by the sea Fjards - 'drowned glacial lowlands'
69
Development of coral
Polyps attach themselves to a hard surface in shallow seas where there is sufficient light for growth. Polyps exude calcium carbonate, which forms their skeleton Polyps have small algae - form a symbiotic relationship with the zooxanthellae
70
Conditions for coral reef formation
> between 23-25 degrees Celcius > most grow at depths of less than 25m > corals prefer shallow water to provide light- algae supply polyps with up to 98% of their food requirements > less than 32 psu (salinity levels) > no sediment - can clog up their feeding structures and cleansing systems > prefer some level of wave action to keep water oxygenated > need to stay submerged
71
Fringing reefs
Fringe the coast of the land | Small and shallow lagoon
72
Barrier reefs
Occur at greater distances from the shore Wide, deep lagoon Older and more continuous than fringing reefs
73
Atoll reefs
Rise from submerged volcanic foundations and often support small islands Very deep, circular lagoon
74
Darwin's subsidence theory
Each stage of coral reefs is a succession of the previous one
75
Daly's theory
**
76
Murray's theory
**
77
Value of coral
1. Seafood - in LICs, coral reefs contribute about 1/4 of the total fish catch, providing food for up to a billion people in Asia alone 2. New medicines e.g. bone grafts 3. Other products - limestone for construction 4. Recreational value - global value of coral reefs estimated to be US $375 billion 5. Coastal protection
78
Anthropogenic threats to coral reefs
1) Global warming* 2) Sea level rise* 3) Overfishing 4) Destruction of coastal habitat 5) Pollution =) according to the WRI, 58% of the world's coral reefs are at high/medium risk of degradation, with more than 80% of SE Asia's extensive reef system under threat
79
Natural threats to coral reefs
1. Dust storms e.g. Sahara | 2. Tsunamis e.g. 2004 Indian Ocean
80
Coral bleaching
When environmental conditions become stressful, zooxanthellae may leave the coral, leaving it in an energy deficit and without colour e.g. 1-2 degree temp. rise Can also be caused by changes in salinity for example

Advanced Physical Geography (3 decks)

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