Block 7 (Aeolian, Fluvial + Biotic Processes, The Characterisation + Formation Of Landforms In Coastal Environments) Flashcards
1
Q
What are aeolian processes?
A
Wind processes
2
Q
What are the landforms associated with aeolian processes?
A
Sand dunes
3
Q
What is a sand dune?
A
Mount/hill/ridge of sand lying beyond the beach’s high tide mark
4
Q
What conditions are needed for a sand dune to form?
A
- Good supply of sand
- Gentle beach gradient
- Area of inland space for dunes to develop
- Onshore winds strong enough to blow sand (greater than its threshold velocity)
- High/macro-tidal range, so sand can dry out + be transported
- Available vegetation for colonisation
5
Q
Outline the process of sand dune formation
A
- Constructive waves deposit sediment on beach
- Onshore winds transport sediment inland when they are above threshold velocity (suspension, saltation, creep)
- Deposition occurs when there is a reduction in velocity (e.g. in lee of obstacle)
- Sand accumulates + pioneer species grow: EMBRYO DUNE
- If sufficient sand accumulates, dunes merge: FOREDUNES (2m)
- More plant colonisation (mainly marram grass) + dunes grow: YELLOW DUNES (10m), that are mobile, moving up to 7m inland/yr
- Between dunes, slacks (lows) form, sometimes with blowouts+lagoons
- At back, GREY DUNES form, high colonisation + humus levels (organic matter in soil from decay) that cause grey colour (lichen), lower as less sediment reaches them
- At very back, MATURE DUNES form, nutrient levels high enough for heath/woodland
6
Q
What is psammosere succession?
A
Vegetation succession on sand (e.g sand dunes)
7
Q
What are the 5 types of dunes in the succession?
A
- Embryo dunes
- Fore dunes
- Yellow dunes
- Grey dunes
- Mature dunes
8
Q
Why do sand dunes move inland?
A
- Wind speeds higher on STOSS side (seaward) - more erosion
- Wind speeds lower on LEE side (landward) - more deposition
- Causes inland dune migration of up to 7m per year
9
Q
What are sand dune blowouts?
A
Areas of bare sand located between sand dunes in dune slacks
10
Q
How do sand dune blowouts form?
A
- Significant vegetation loss (waves, animals, humans, etc)
- Wind removes sand - DEFLATION (as no stabiliser)
- Windward slope (at back) steepens - wind flow increases, increasing deflation rates (POSITIVE F)
- When water table reached, deflation stops, sand too wet for transportation (LAGOON left)
11
Q
Why are plants needed for sand dune formation?
A
Their colonisation binds sand, stabilising dunes so they can develop + grow
12
Q
What is a pioneer species?
A
First species to colonise dunes - closest to sea
- E.g. Lyme grass + sea couch
13
Q
What is climax vegetation?
A
Last species to colonise dunes - furthest from sea
- E.g. trees
14
Q
What adaptations do plants have to grow in the sand dune system?
A
- Low growing (to deal with harsh winds)
- Halophytic - salt tolerance (to deal with high salinity)
- Xerophtic - drought resistant (to deal with low water levels)
- Able to cope with low nutrient levels
15
Q
Give an example of vegetation found on each type of sand dune
A
- Embryo: Lyme grass + sea couch (PIONEER)
- Fore: Marram grass
- Yellow: Marram grass
- Dune slacks: Rushes (in water)
- Grey: Lichen + parasol mushrooms
- Mature: Trees, bushes, heath (CLIMAX)
16
Q
What is the most important species in sand dune formation?
A
Marram grass
- Not the pioneer species, but most important in holding sand together to allow dune growth
- Mainly in fore + yellow dunes
17
Q
What adaptations does marram grass have?
A
- Low growing, 60-120cm tall (to combat winds)
- Halophytic
- Underground root system + methods to reduce water loss via transpiration, e.g. rolled leaves, sunken stomata, waxy cuticle (to combat low water levels)
18
Q
What are fluvial processes?
A
Processes associated with rivers + streams
19
Q
What are estuarine environments?
A
Area in which a river flows into the Sea
- Affected by fluvial + marine processes
- Low energy, deposition also areas
20
Q
What are the main sediment sources in estuarine environments?
A
- Fluvial/land based
- Estuary margin
- Outside estuary (LSD)
21
Q
What are the major landforms associated with estauries?
A
- Tidal Mudflats
- Salt marshes
22
Q
What are the micro-features associated with estuarine environments?
A
- Channels
- Rills
23
Q
What are channels?
A
Indents through which running water flows
24
Q
What are rills?
A
Shallow channels
25
Where are the channel + rill micro-features found?
In estuarine environment - on tidal flats + salt marshes (as water flows over landform, from river out to sea)
26
What is a tidal mudflat?
Extensive, unvegetated depositional area bordering estuary
27
Where are tidal mudflats found?
- In estuary, at edges where energy is lowest
| - Intertidal zone (covered at high tide, uncovered at low tide)
28
What two processes do tidal mudflats notably experience?
- Sediment sorting
| - Bioturbation
29
Why does sediment sorting happen on tidal mudflats?
Differences in energy throughout estuary
- Highest energy: most seaward (receives wave + tidal energy) + most landward (receives river current energy) points
- Lowest energy: central zone (particularly edges of central zone)
30
Where is coaser sediment deposited through sediment sorting on tidal mudflats?
- Most seaward + most landward parts (not enough energy when move into centre to continue carrying large calibre)
31
Where is finer sediment deposited through sediment sorting on tidal mudflats?
- Central part (small enough to carry into low energy zone where it is deposited)
32
What is bioturbation?
Organisms (e.g. lugworms) churning up mudflats by burrowing
33
Give an example of a tidal mudflat
Afon Mawddach, West Wales
34
What is a salt marsh?
Gently sloping, vegetated areas of intertidal mudflats
35
Where are salt marshes found?
- Intertidal zone
| - In low energy areas with deposition: estuaries+behind spits/bars
36
Outline the process of salt marsh formation
- Deposition of mud where river + wave energy is low (mudflat)
- Pioneer species (halophytic) colonise, encouraging more deposition
- Height of marsh increases
- Secondary colonisers invade, succeeding pioneers (closer to land)
- More deposition + height growth, until less halophytic plants can succeed closer to land
- Areas furthest from water become more terrestrial than marine, colonised by climax veg, e.g oak trees
37
Moving inland in a salt marsh, how does salinity + tidal exposure change
- Decreasing salinity
- Decreasing tidal exposure
(So plants inland don’t need to be as adapted as pioneers)
38
What are the two zones in a developed salt marsh?
- Mudflats: covered at normal high tide, uncovered at normal low
- Sward zone: only covered at spring high tide
(At very back of these zones are the climax species)
39
What is a halosere succession?
Succession characterised by high salinity
| - E.g salt marsh
40
Give examples of 2 pioneer species in a salt marsh
- Salicornia
- Spartina
(Can tolerate harsh conditions: frequent tide cover, high salinity)
41
Give examples of 2 sward zone species in a salt marsh
- Sea lavender
- Sea thrift
(Can tolerate medium conditions: covered by spring tide, medium salinity)
42
Give examples of 2 climax species in a salt marsh
- Ash tree
- Oak tree
(Terrestrial: not covered by tides, low salinity)
43
Give an example of a salt marsh
Salt marshes on Essex Coast - ‘The Saltmarsh Coast’
| Between Blackwater + Crouch estuaries
44
What are biotic processes?
Processes completed by living beings
- Coral reefs
- Mangroves
45
What is a coral reef?
Underwater ecosystem made up of coral polyp colonies held together by calcium carbonate
46
Outline how coral reefs form
- Made up of polyps (small, soft-bodied organisms from jellyfish family)
- Polyps secrete protective skeleton made from calcium carbonate, that connects them to each other + the seabed
47
How do cold water polyps get their food?
Catch food in tentacles as it moves past them in current
48
How do warm water polyps get their food?
Get energy from SYMBIOTIC relationship with ZOOXANTHELLAE
- Mutually benefit
- Zooxanthellae get nutrients + shelter
- Polyps get food (zooxathellae are algae that photosynthesise + share their food with polyps)
49
What gives coral reefs their colour?
Zooxathellae living on polyps photosynthesising
50
Where do cold coral reefs form?
- Deep cold water
- Recently discovered (advance in deep sea tech)
- Corals work independently - no zooxanthellae
51
Give an example of a cold coral reef
Darwin Mounds, Scotland
- 1000 m under North Atlantic
- First discovered in 1998
52
Where do warm coral reefs form?
- Approx 30degrees either side of Equator
In specific conditions:
- Temp: 23-29C
- Water depth: less than 100m (need light + water coverage)
- Salinity: 30,000-40,000 ppt
- Light/clear (for zooxathellae photosynthesis)
- Clean
- Well-aerated from good wave action(need good oxygen supply)
53
Where are most coral reefs found?
In warm water
| - 91% in Indo-Pacific region
54
What happens if reef conditions change?
- Polyps are very sensitive
- Changes cause them to stress (e.g sea level rise + pollution)
- Stressed polyps expell zooxathellae - CORAL BLEACHING
- Polyps lose their food provided by the symbiotic relationship
- Can die if left unhelped
55
What proportion of the world’s coral reefs have died in the last 30yrs?
Over 50%
56
How many reefs will suffer at least one bleach over the next 50yrs?
Every reef
57
Why are coral reefs important?
- Natural coastal defence (waves break offshore)
- Natural carbon sink (store CO2 in calcium carbonate skeletons)
- Great biodiversity (cover 1% ocean floor, home to 25% ocean species)
- Potential medical benefits (half research for new cancer drugs is using marine organisms)
- Food source (can yield 15 tonnes seafood/km sq per year)
- Employment (tourism, conservation, fisheries)(supports livelihood of over 100 mill people)
- Economic contributor (boosts tourism - revenue $30 bill per yr)
58
What are the three types of coral reef?
- Fringing
- Barrier
- Atoll
59
What is a fringing coral reef? Give an example
Reef directly attached to the shore or separated by only a small channel or lagoon
- E.g. South Molokai, Hawaii
60
What is a barrier reef? Give an example
Reef separated from shore by a deep channel/lagoon
| - E.g. Great Barrier Reef
61
What is an atoll reef? Give an example
Roughly circular reef with lagoon in middle, that has risen from submerged volcanic foundations
- E.g. in the Maldives
62
What are the human threats to coral reefs?
Fishing
- Overfishing can cause algal growth, reducing sunlight
Agriculture
- Land clearing increases surface run-off which reduces sea clarity
- Chemical pesticides/fertilisers can damage corals
Tourism
- Removal of veg for development, increases surface run off, decreases sea clarity
- More sewage, nitrogen + phosphate near sewage pipes, algal growth
- Demand for more energy, release hot water, raises sea temps
- Destruction for souvenirs
- Diving + snorkelling activities disrupt environment
- Increased waste + pollution
63
What are the natural threats to coal reefs?
Hurricanes
- Often produce powerful waves, can destroy coral
- Heavy rainfall increases surface run off, decreasing sea clarity
Global warming
- Fewer areas remain 23-29C all yr
- More threatening events, e.g hurricanes + heatwaves
- CO2 level increase makes sea more acidic, calcium carbonate production harder
Coral diseases
- Approx 30 diseases known about
- Little known about cause + effect, so hard to prevent
- 80% coral lost in last 20 yrs was to disease
64
What are mangroves?
Group of tree species that can tolerate high salinity
65
Approximately how many mangrove tree species are there?
100
66
What are mangrove forests?
Intertidal zones that have been colonised by mangrove trees
67
How are mangrove forests different to salt marshes?
Mangrove forests have greater biomass
68
Where are mangroves found?
- Across 118 countries
- Intertidal zone
- Often in nutrient-rich estuaries or deltas
- Most in S+SE Asia (over 40%)
69
What are the conditions in mangrove forests?
- Fertile soil
- Waterlogged/anaerobic
- High salinity
- Affected by tides
70
What are some adaptations of mangroves to deal with conditions in mangrove forests?
- Pneumatophores (straw-like roots that stick out above waterlogged mud to take in oxygen via pores called lenticles)
- Arenchyma (porous roots below ground with air spaces to improve oxygen flow)
- Salt glands on leaves (allow secretion of excess salt)
- Waxy cuticles on leaves (reduce water loss)
- Seeds remain attached until fertilised (improves reproduction)
71
Why are mangroves important?
- Large biodiversity (including some unique/endangered species)
- Carbon sink (soils intake double as much C/yr as salt marshes)
- Natural coastal defence
- Fishing (fish habitat - provides food + work)
- Resources (medicines, timber, fertile farming soil, etc)
- Symbiotic relationship with coral reefs (coral reefs absorb wave energy, mangroves trap sediment to keep water clear)
72
What is a symbiotic relationship?
Cooperative, mutual relationship between two species
73
If left naturally, are mangroves threatened?
Not particularly - on average growing, reclaiming 3mm from sea/yr
74
How are humans threatening mangroves?
- Overharvesting resources
- Clearing for agriculture/settlements
- Shrimp aquaculture
- Overfishing
- Damming rivers upstream
- Pollution (e.g oil spills suffocate trees)
- Reef destruction/bleaching (destroys symbiosis)
- Eustatic sea level rise from climate change (cancelling out land regain)
75
Give two examples of coral reefs
- Caribbean coral reefs
| - Great Barrier Reef
76
Give an example of a mangrove
The Sundarbans
77
Give an example of a mangrove plant
Avicennia Marina (‘grey mangrove’)
