Coastal Environments And Coastal Fieldwork Flashcards
1
Q
What are constructive waves
A
- Low energy waves
- Long wavelength
- Shallow gradient waves
- Occurs in calm conditions, without much wind
- Strong swash
- Weak backwash
Beach built up by deposition of material brought up in wash
2
Q
What are destructive waves
A
- High energy waves
- Tall waves with short wavelength
- Steep gradient waves
- Weak swash
- Strong backwash
Beach is receded
3
Q
What is fetch
A
The length of time and distance over open water that the wind has blown to create a wave
4
Q
What are the physical marine processes types of erosion
A
- Hydraulic action
- Abrasion
- Solution (Corrosion)
- Attrition
5
Q
What is hydraulic action
A
Waves hit cliffs and force air into cracks, cracks get bigger over time and break apart the cliff
6
Q
What is abrasion
A
Waves pick up pebbles and hurl them against the cliff
7
Q
What is Solution (corrosion)
A
The dissolving of CaCO3 (calcium carbonate) rocks (e.g. limestone or chalk) by the sea
8
Q
What is attrition
A
Pebbles carried by the waves collide with each other and become smaller and more rounded over time
9
Q
What is deposition
A
Occurs when waves lose energy or the material carried is too large to transport with the amount of energy the wave has
10
Q
How is sediment transported
A
- Longshore drift
- Solution
- Suspension
- Saltation
- Traction
11
Q
What is longshore drift
A
- Wave swash approaches the beach at a 45° angle (the same as the prevailing wind direction)
- This is in conditions where wave refraction is not complete
- Backwash is at a 90° angle, due to gravity
- The process repeats, moving sediment along the beach
- Smaller material is transported further as it requires less energy
12
Q
What is prevailing wind
A
The prevailing wind is the direction which the wind normally blows from
13
Q
What is solution (transportation)
A
When minerals in rocks like chalk and limestone are dissolved in sea water and then carried in solution
14
Q
What is suspension
A
Small particles such as silts and clays are suspended in the flow of the water
15
Q
What is saltation
A
Where small pieces of shingle or large sand grains are bounced along the sea bed
16
Q
What is traction
A
Where pebbles and larger material are rolled along the sea bed
17
Q
What is weathering
A
When rocks break down in situ (on site), which is different from erosion which requires transportation of rocks and minerals by agents (e.g. water)
18
Q
What are the 3 different types of weathering
A
- Mechanical weathering
- Biological weathering
- Chemical weathering
19
Q
What is mechanical weathering
A
Mechanical weathering breaks down rocks by processes such as freeze-thaw, salt crystal growth, and wetting and drying of clay rich rocks
20
Q
What is freeze thaw
A
- Water enters cracks in the rock
- When temperatures drop, the water freezes and expands causing the crack to widen
- The ice melts and water makes its way deeper into the cracks
- The process repeats itself until the rock splits entirely
21
Q
What is salt crystal growth weathering
A
- As seawater splashes onto rocks, it evaporates, leaving behind salt crystals
- As these crystals grow, they pressure the rock, causing pieces to break off
22
Q
What is the process of wetting and drying of clay rich rocks
A
Constant swelling and shrinking makes rocks crack (stress on rock)
23
Q
What is biological weathering
A
When rocks are broken down by plant roots, burrowing animals and nesting birds
24
Q
What is chemical weathering
A
When rocks are broken down by carbonation, oxidation and acid rain, usually impacts CaCO3 rock
25
What is carbonation
Occurs when carbon dioxide from moisture in the air reacts with carbonate minerals found in rock, this creates carbonic acid which breaks down rock
26
What is oxidation
Oxidation occurs when oxygen reacts with minerals such as calcium and magnesium to form iron oxide, iron oxide is reddish brown in colour and causes the decomposition of rock
27
What is slumping
Waves erode the cliff base and cause instability, rainwater permeates through the rock, saturating it, until it becomes unstable and slumps along bedding planes; it leads to a stepped appearance to the cliff
28
What is sliding
Weathering loosens rock, which slides down off bedding planes; leads to landslides and mudslides
29
What are bedding planes
A line in rocks separating two different layers, with one usually more resistant to erosion, one usually weaker
30
What is geology
Rock type e.g. granite, chalk e.t.c
31
What is lithology
Characteristics of the rock e.g. relative hardness, permeability e.t.c
32
What is discordant geology
Rock outcrops are at 90° to the sea; leads to headlands and bays where there are bands of soft and hard rock interspersed with each other
33
What is concordant geology
Rock outcrops are parallel to the sea; creates straighter coastlines, though can create coves, like Lulworth Cove, Dorset
34
What do bedding planes in cliffs determine
How susceptible the cliff is to collapse
35
Order of fastest erosion because of bedding planes
1. Diagonal planes to the sea (slides/slumps easily)
2. Vertical (topples)
3. Horizontal (can be undercut, but will not easily collapse)
4. Diagonal planes away from the sea (gravity pulls planes ‘away’ from the sea, very resistant to erosion)
REMEMBER - The type of rock also impacts erosion (soft or hard rock)
Check exam notes on Goodnotes for diagram of bedding planes
36
How does vegetation influence the coast
- Biological weathering
- Can create sand dunes via encouraging deposition, and then stabilise them
- Can protect and preserve coastal landforms by buffering and reducing wave energy (e.g. mangroves)
37
How does sea level influence the coast
- Flooding; a huge issue associated with rising sea level, especially considering many urban areas are situated on the coast
- Saltwater incursion
- Creation of landforms (different dependent on whether sea levels are rising or falling - remember this is different in different parts of the world)
38
What is saltwater incursion
When salt water from the sea contaminates drinking water, impacting locals
39
What is isostatic readjustment
- Land level rises or falls relative to the sea, so it appears that sea level is falling or rising
- Leads to relict (old) landforms
- Emergent landforms (falling sea level) = raised beaches and cliffs
- Submergent landforms (rising sea level) = rias (drowned river valleys) and fjords (drowned glaciated valleys)
40
What is Eustatic change
Ice on land e.g. Greenland ice sheet or Antarctic ice sheet melts and adds water to the oceans, leading to actual sea rise
41
What is thermal expansion
As water gets warmer it expands, so as seas warm due to climate change it will expand and cause sea levels to rise
42
How do people influence the coast
- Settlements
- Fishing
- Trade
- Tourism
43
What is the influence of wave refraction
- Waves approach parallel to the coastline as a whole
- As the sea shallows, on approach to the coast the waves refract to mirror the individual shape of the coastline
- This leads to energy being concentrated on headlands (due to converging waves) more than in bays (due to diverging waves), despite this, headlands remain sticking out to sea more than bays due to their relatively harder lithology
44
What are converging waves
Waves that meet at a point, wave energy is concentrated
45
What are diverging waves
Move in different directions (not centred at a point), wave energy is diffused
46
How do cliffs erode and retreat
- Erosion is concentrated at the base of the cliff between the low tide and high tide mark in the wave attack zone
- This creates a wave cut notch
- The cliff below is undercut, is therefore unsupported and collapsed due to gravity
- This creates a wave cut platform
- Over time, this repeats and the cliff retreats inland
47
What is a wave cut notch
An area of erosion at the base of a cliff formed by the waves, its formed by erosional processes such as abrasion and hydraulic action
48
What is a wave cut platform
A flat area in front of a cliff, just below the low tide mark; these were formed when the waves eroded the cliff, but left a flat platform behind
49
What is undercutting
The erosion of material at the foot of a cliff or steep bank, ultimately the overhang collapses and the process is repeated
50
What are the stages of cliff retreat
1. Sea attacks base of cliff
2. Wave-cut notch
3. Cliff collapses
4. Wave-cut platform
5. Cliff retreats
51
What are headlands eroded down to
Cave —> Arch —> Stack —> Stump
It is the retreat of a cliff by marine processes
52
How are caves formed
1. Cracks at the base of the headland within the inter-tidal zone become exposed through hydraulic action, which pressurises air, forcing the crack to open
2. Cracks are further widened by weathering processes such as salt crystallisation and wet and dry weathering that affects chalk
3.Over time the cracks widen and develop wave-cut notches - further processes of abrasion and hydraulic action will deepen the notch to form caves
53
How is an arch formed
1. As a result of wave refraction, which distorts the wave direction, destructive waves concentrate their energy on the sides; this deepens the cave
2. Wave refraction effects all three sides of the headland - if two caves are aligned, the waves may cut through to form an arch; wave-cut notches widen the base of the arch
54
How are stacks formed
1. Vertical joints are exposed by tall breakers associated with destructive waves; joints can also be weathered from above such as through carbonation in limestone - here blowholes may form (roof of cave falls, leaving a gap in the top of the cliff through to the cave)
2. Over time the arch becomes unstable and collapses under its own weight to form a pillar of rock, called a stack
55
How are stumps formed
1. The stack is further eroded at its base creating new wave-cut notches; sub-aerial processes continue to weaken the stack from above
2. Eventually the exposed stack will collapse to form a stack - the broken material is further eroded through attrition and transported away to be deposited within the bay
56
What are the erosional landforms
- Bays and headlands
- Cliffs and wave cut platforms
- Cave, arch, stack, stump
57
What are the depositional landforms
- Beaches
- Spits and bars
- Tombolos
- Cuspate forelands
58
What are beaches
- Areas where there is an accumulation of sand and shingle, caused by deposition
- They often forms in bays, where the coast is sheltered from high energy, erosional waves, or where longshore drift provides a large supply of material
59
What is a spit
- Long, narrow, beaches of sand or shingle, attached to the land at one end
- They extend across bays or river estuaries, wherever the coastline changes direction
60
How is a spit formed
1. Sudden change in coastline shape/direction
2. Longshore drift has momentum and so continues to transport and deposit material at sea, following the original direction of longshore drift
3. Over time, sediment builds up creating a sandy ridge outcrop (a spit) on the coast
4. Salt marshes often forms behind spits as these waters are low energy and stagnant (not flowing). Rivers often deposit their sediment too, growing the spit
5. Spits often become curved due to secondary prevailing wind or the impact of cross-currents/storms
6. The spit is stopped from blocking the entire estuary by the river eroding and removing material from the end
61
How is a bar formed
- Formed as a spit grows across a bay, joining up two headlands
- Lagoon (area of water dammed by the bar) will be gradually infilled by deposition
62
How is a Tombola formed
A spit grows out from the mainland and joins to an island
63
What are cuspate forelands
- Triangular shaped accumulations of sand and shingle
- Develop due to longshore drift from two directions
- Collision of two longshore drift directions encourages deposition and creation of the foreland
64
What distinctive ecosystems develop along particular stretches of coastline
- Coral reefs
- Mangroves
- Sand dunes
- Salt marshes
65
What is the distribution of coral reefs
Found between 30° north and south of the equator
66
What are the limiting factors of coral reefs
- Sea surface temperature (SST) of 23-25°C
- <25m deep water (as sunlight needed)
-Salinity
- Clean water, with not too much sediment that would otherwise clog feeding structures
- Moderate wave action
67
What are coral reef features
- Cover 1% of the ocean floor but have 25% of marine biodiversity (variety of life in oceans and seas) contained within
- Composed of coral polyps (animals) that have a symbiotic relationship with algae
- Provide several ecosystem goods and services (regulating, provisioning, supporting, cultural)
68
What does biotic factors mean
Living factors
69
What does abiotic factors mean
Non-living ecosystem components
70
What are biotic factors of coral reefs
- Coral
- Algae
- Fish
- Sharks
- Turtles
- Plankton
- E.t.c.
71
What are abiotic factors of coral reefs
- Temperature
- Water flow
- Salinity level
- pH of seawater
- Light level
- Nutrient availability
72
Nutrient cycling in a coral reef
1. Nutrient source (Sea water; corals filter nutrients out of seawater)
2. Biomass (Coral, algae, seaweed, fish, crustaceans and invertebrate species)
3. Litter (Dead coral, fish, invertebrates, seaweeds e.t.c. - moved around by tides and ocean currents)
Cycle repeats
73
Coral reef food web
Large shark -> Tuna -> Mackerel -> Small fish -> Shrimplike creatures -> One-celled life
74
How are reefs threatened by tourism
- Accidental trampling
- Carrying capacity could be exceeded
75
How does industrialisation threaten coral reefs
- Water pollution
- Air pollution -> Rising temperatures -> Rising ocean temperatures -> Coral bleaching
76
How does agriculture and deforestation threaten coral reefs
Increased runoff -> Increased siltation fertiliser runoff -> Eutrophication -> Decline in water quality
77
What is coral bleaching
- Coral bleaching occurs when corals are stressed by changes in their environment, the coral stresses out and expels the algae; as the algae leaves, the coral fades until it looks like it's been bleached
- If it doesn’t let the algae back, the coral dies
78
Mangroves distribution
- 32° north - 32° south of the equator
- Sheltered, intertidal areas, that receive high annual rainfall
79
What are limiting factors of mangroves
- An average temperature of the coldest month to be higher than 20°C
- Fine-grained substrate or sediment
- The shores must be free of strong wave action and tidal current
- Salt water
80
What are the features of mangroves
- Traps silt; creating new land
- Provides timber for building materials
- Provides protection from storms, storm surges and tsunamis
81
How are mangroves threatened by industrialisation, agriculture, tourism and deforestation
- Timber for fuel and building material
- Aquaculture
- Land reclamation for tourist hotels and other amenities
- Diversion of fresh water
- Farming requires application of herbicides to prepare for cultivation
82
What is aquaculture
Aquaculture is the practice of farming seafood - it's like agriculture, but done with fish, crustaceans and shellfish
83
What is the distribution of sand dunes
Form worldwide at the interfaces between land and sea
84
What are limiting factors of sand dunes
- Wide beach and large quantities of sand
- Onshore prevailing wind (from the sea to the shore)
- An obstacle e.g. marram grass, driftwood e.t.c. to encourage deposition
85
What are features of a sand dune
- Plant succession (the development of plants in a particular area) on the dunes is called psammosere succession (stabilise sand and encourage more sand to accumulate there)
- Embryo dunes, foredunes, yellow dunes, grey/mature dune is the sequence for dune formation from youngest to oldest
- Dune slacks form in between dune crests
- Mature dunes contain more humus (organic matter) than embryo dunes and they have a more acidic pH due to the absence of sea shells
86
How are sand dunes threatened by tourism and recreation
Recreation e.g. trial biking and horse riding; golf courses and caravan sites
87
What is the distribution of salt marshes
- In intertidal zones, separating permanently flooded mudflats and dry, inland areas above the high tide mark
- Usually in sheltered areas of coastline such as estuaries or bays and are usually behind spits
88
What are the features of salt marshes
- Either adapted to saltwater (if in bays) or brackish water (if in estuaries) which is part fresh water, part salty water
- Mudflats are colonised by vegetation over time, until the most stable climax community vegetation of Carr woodland is achieved at the back of a salt marsh (this is permanently waterlogged)
89
How are salt marshes threatened by industrialisation, agriculture and tourism
- Reclamation to create farmland and sites for industrial and port developments
- Industrial pollution from ports, power stations and oil refineries
- Agricultural pollution from fertilisers and pesticides
- Pressures from developments such as marinas and other recreational facilities
90
How are salt marshes formed
