Coasts: Why are coastal landscapes different and what processes cause these differences EQ1 Flashcards
(72 cards)
1
Q
What type of system is the coast viewed as?
- what do this mean it has?
A
An open & closed system
- inputs, outputs, stores & transfers
2
Q
What does the littoral zone contain? (give an example)
A
Many sediments
(e.g. pebbles & sand particles)
3
Q
How are the sediments moved around in the littoral zone?
A
By waves, current & tides
4
Q
What are the four subzones of the littoral zone?
A
- Backshore
- Foreshore
- Nearshore
- Offshore
5
Q
What is the Offshore?
A
Area of deeper water beyond the point at which waves begin to break
6
Q
What is the Nearshore?
A
Area of shallow water beyond low tide mark. Friction between seabed & waves distort the waves making them break
7
Q
What is the Foreshore?
A
Area between hide tide and low tide mark.
8
Q
What is the Backshore?
A
Part of the beach lying between the beach face and the coastline.
9
Q
What is the Breaker/Surf zone?
A
Where waves break as a consequence of depth limitations and surf (foamy bubbly surface) onshore as waves bore (change in depth)
10
Q
What are berms?
A
Terrace of a beach that has formed in the backshore, above the water level at high tide.
11
Q
What does the system strive to be in a state of?
A
Dynamic equilibrium
12
Q
Stores on a coast:
A
- Beach
- Cliffs
- Dunes
- Marshes
13
Q
Inputs: natural processes examples
A
- Sediments from the sea
- Weathering & mass movement occuring on the backshore
- Constructive and deconstructive waves casing deposition and erosion
- Longshore Drift
14
Q
Inputs: Human activity examples
A
- Dredging of rivers to make them deeper for shipping
- dredging of offshore areas to get sand and gravel for construction
- The building of coastal defences against erosion and flooding
15
Q
Examples of Outputs:
A
- Evapouration
- Sediment transfer
16
Q
Examples of Transfers:
A
- Wind-blown sand
- Mass movement processes (landslide)
- Longshore drift
- Weathering
- Erosion
17
Q
What 2 long-term factors affect coastal systems?
A
- Geology
- Changes in sea level
18
Q
What are the 3 contrasting coastlines?
A
- Rocky coastline
- Sandy coastline
- Estuarine coastline
19
Q
What are the other 2 main type of coastline?
A
Concordant & Discordant coastlines
20
Q
Sea level change:
What 2 things can sea level occur as a result of?
What can long-term sea level change be?
- what two different coastlines do these lead to?
A
- Global warming
- Tectonic activity
- Eustatic= when sea level itself changes
- Isostatic= when land rises or falls relative to the sea
- Emergent or Submergent
21
Q
What 4 short-term factors affect coastal systems?
- these create coastlines that can be…?
A
- Waves - destructive/constructive
- Tides - high/low tide
- Rivers
- Storm events
- Retreating or advancing
- dominated by land-based processes (primary coasts) or marine processes (secondary coasts)
- large or small tidal range
- high or low energy
22
Q
Characteristics of Low-energy coastlines:
- Waves
- Processes
- Landforms
- General Location
+ example location
A
Waves:
- Constructive waves (less powerful)
- Short fetches (generate smaller waves)
Processes:
- Rate of deposition exceeds erosion
- Sediments from rivers, longshore drift & nearshore currents
Landforms:
- Beaches, spits, salt marshes, sand dunes, bars, mudflats
General Location:
- sheltered from large waves e.g. by headlands or spits
- Lowland coasts
- Coastal plain landscape
Example:
- Norfolk Coastline
23
Q
Characteristics of High-energy coastlines:
- Waves
- Processes
- Landforms
- General Location
+ example location
A
- Face large oceans & exposed
Waves: - Destructive waves (more powerful)
- Long fetches (generate larger waves)
Processes: - Rates of erosion exceeds deposition
- Sediments from eroded land, mass movement and weathering, offshore currents
Landforms: - cliffs, headlands, wave-cut platforms, arches, sea caves, stacks
General location: - Exposed to largest waves
- Highland and lowland coasts
- Rocky coasts
Example: - Happisburgh
24
Q
How are rocky coasts formed?
- what type of cliffs are found?
- what is more dominant, erosion or deposition?
- what two type of erosion dominate?
A
- Where there is more resistant rock
Steep cliffs= typically high-energy environments
Cliffs with gentler slope= typically found in low energy environments
Erosion= Marine erosion (action of waves) & Sub-aerial erosion (weathering & mass movement)
25
When do Coastal plain landscapes occur?
- how do they form?
- where does the sediment come from?
- do they tend to be high or low relief?
- what 2 coastlines do coastal plains include?
- what kind of environments are they?
- what form here to help stabilise the coast & reduce erosion?
- what else may occur here due to poor drainage?
When land gradually sloped down towards the sea
- when deposition exceeds erosion
- terrestrial & offshore sources
- low relief
- Sandy coastlines & Estuarine coastlines
- low energy environments
- sand dunes
- wetlands & marshes
26
Where are Estuarine coastlines formed and what are they formed from?
At the mouth of rivers and are formed from clay and silt
27
Concordant coastline:
Arrangement of rock types on a large scale are parallel to the coast, meaning the alternating hard and soft rocks lie in the same direction as the coastline.
- More resistant rocks form elongated Islands
- Less resistant rocks form coves
Example: Lulworth Cove (Dorset coast)
28
Discordant coastline?
Arrangement of rock types on a large scale is at a right angle to the coast with alternating hard and soft rock bands.
- More resistant rocks form headlands
- Less resistant rocks form bays
Example: Happisburgh, Norfolk
29
Discordant coasts & wave refraction:
- what does wave refraction change?
- where is wave energy concentrated? what does this mean?
- changes amount of energy reaching the shore
- concentrates at the headland= increases rate of erosion
30
What is coastal morphology?
The shape and form of the coastline
31
What 2 factors does geology include?
- what does geology influence?
1. Rock type
2. Rock structure
- Influences morphology and erosion rates
32
What is the geology of Lulworth cove? (concordant coastline)
- how is the cove created?
More resistant limestone runs parallel to the sea with the less resistant limestone and clay behind it
- when water has broken through at weaker points in the more resistant limestone & the rate of erosion has increased due to the less resistant limestone and clay behind= cove
33
What is the geology like in Happisburgh (discordant coastline)
- what happens to the soft material?
- what does this lead to the formation of?
composed of a layer-cake sequence of several glacial tills, separated by beds of stratified silt, clay and sand
- soft material erodes rapidly
-headlands and bays
34
What are the 2 other examples
of concordant coastlines?
Dalmatian coastline & Haff coastline
35
Haff coastline:
- what type of coastline is it?
- where is an example of this?
- what does it consist of?
- where do they form?
- what is there deposition of?
- depositional version of a concordant coastline
- South coast of the Baltic sea (by Poland & Lithuania)
- long spits of sand that alternate with lagoons
- consists of long spits of sands and lagoons
- in low-energy coastlines
- There is deposition of muds and sands
36
Dalmatian coastline:
- what type of coastline is it?
- what is it dominated by?
- where is an example of this?
- what does it consist of?
- how does the rock strata lie?
- concordant coastline
- dominated by harder material
- Croatia
- series of hills and valleys which were exposed during times of lower sea level
however rising seas have inundated the valleys so now left as islands sticking up from surface
- lies parallel to the main coastline
37
What is meant by cliff profile?
- what influences cliff profiles?
Angle and height of the cliff face
(e.g. steep, tall, sloped)
- geology & the dip of rock strata
38
What is lithology?
The physical characteristics of particular rocks
39
Lithology characteristics:
- Strata
- Bedding planes
- Joints
- Folds
- Faults
- Dip
40
What is strata?
Layers of rock
41
What are Bedding planes?
- what do they increase exposure to?
Horizontal cracks caused by pauses in rock formation
- erosion
42
What are Joints?
- what 2 things do they increase exposure to?
Vertical cracks 90 degrees to the bedding plane caused by tectonic movement or contraction
- erosion & weathering
43
What are Folds?
- where is there an example of this?
- what does this do to the rock?
- what does this speed up?
The result of pressure during tectonic movement causing the rock strata to fold
- Lulworth 'crumple'
- weakens the rock
- erosion
44
What are Faults?
Faults are major fractures in rock created by tectonic forces, with displacement of rocks either side of the fault line
45
Whats is a Dip?
- The angle at which rock strata lie
e.g. Horizontally, vertically, dipping towards to sea or dipping inland
46
What is coastal recession?
The retreat of the coastline inland
47
What does permeable mean? Give an example of a permeable rock
- what can also make rocks permeable?
What else can rocks have that make them permeable?
(give an example of a rock that has this)
Rocks with spaces, or pores that water can pass through the rock
Example: limestone
- if they have lots of cracks, joints and bedding planes (e.g. limestone as well)
- pores within them= allow water to pass through (e.g. chalk)
48
What does impermeable mean? Give an example of a permeable rock
Rocks that do not have spaces or many joints so do not let water in
Example: Granite
49
What are subaerial processes? Examples
Land-based processes that occur above the waterline
Examples: weathering, mass movement
50
What type of rocks are more resistant to marine erosion and weathering? why?
Igneous rocks (consists of cooled magmas)
e.g. granites, basalts
51
What type of rocks are less resistant to marine erosion and weathering? why?
Sedimentary rocks (formed underneath oceans)
e.g. limestones, sandstones
52
What are the 3 different types of rock?
1. Igneous
2. Sedimentary
3. Metamorphic
53
Igneous rocks
- how do they form?
- give 2 examples of Igneous rocks
- what are these rocks like with erosion and weathering?
- what do these rocks have that make them very resistant to sub-aerial processes?
- what do they have few of compared to other rocks?
- when molten rock from earth's mantle cools & hardens
- Granite, Basalt
- erode and weather very slowly
- interlocking crystals
- fewer joints and weaknesses
54
Sedimentary rocks
- how do they form?
- give 2 examples of sedimentary rocks
- what are these rocks like with erosion and weathering?
- these rocks have weak...?
- these rocks are heavily...?
- what do these rocks have many of?
- form in layers as a result of compaction & cementation of sediment underneath the ocean
- limestone, sandstone
- erode and weather more rapidly
- have weak bedding planes
- heavily joined
- bedding planes and fractures
55
Metamorphic rocks
- how do they form?
- give 2 examples of metamorphic rocks
- what are they more and less resistant than?
- what makes them weaker than Igneous rock (structure wise)?
- when sedimentary and igneous rocks are altered through heat and pressure, without melting
- slate, marble
- more resistant than Sedimentary rocks/ less resistant than Igneous rock
- the crystals have a parallel alignment= weaker
56
What happens when permeable rock overlies impermeable rock?
- what does this then lead to and why?
The permeable rock is vulnerable to mass movement bc the additional weight and lubrication the water creates leads to instability
57
On a discordant coastline what type of coastal landforms does erosion lead to?
Headlands & Bays
58
What is the term for the changing rates of erosion of different rock types?
Differential erosion
59
Where are salt marshes and sand dunes found?
Lowland UK areas
60
What is vegetation good for?
Stabilising soft sediment low energy coastlines based on sand & mud
61
What are the 3 ways vegetation helps stabilise a coastline?
1. Plant roots help bind soil/sand together= reducing impact of erosion
2. Wind speeds reduced= decreases erosion & increases deposition
3. Dead plant material adds organic matter to sand= eventually lead to formation of soil
62
What is plant succession?
When plant communities change over time in a given area due to an area of initially bare sediment being colonised
63
How does plant succession happen?
- Pioneer plants change the conditions of the soil by adding humus (decayed vegetation)
- retain moisture
- stabilise loose sand or mud
- Eventually new plants take over
- This continues until there is a balance between all natural factors and the vegetation
64
What are sand dunes known as?
Psammosere - where xerophytic plants (e.g. marram grass) can survive with little fresh water
65
What are salt marshes known as?
Haloseres - with halophytic plants (e.g. samphire) can survive in salty conditions
66
Where are salt marshes found?
Low-energy environments of estuaries and sheltered bays
*as well as behind a spit which sometimes forms across the mouth of an estuary
67
How are salt marshes formed?
1. Tidal conditions bring seawater & sediments in and out
2. Fine muds & silts are deposited at the sides of the estuary by rivers
3. Tiny clay particles stick to each other (flocculation) then are colonised by algae
4. pioneer plants have to survive being covered with slightly salty water 2x a day
5. Overtime the plant changes the conditions by trapping more sediment, which builds the salt marsh up, so other plants can then colonise
68
Where are sand dunes formed?
where there is a plentiful supply of sand
69
How are sand dunes formed?
1. Large areas of sand must dry out
2. onshore winds blow sand towards the land
3. vegetation or shingle ridges trap the sand
4. Embryo dunes form first, they collect more sand & get larger
5. pioneer plants (e.g. sea rocket) are able to colonise the stable dunes and help to hold sand together & trap more sand
6. Between 50-100 years is when a significant dune sequence develops (oldest dunes closest to land & youngest closest to the sea)
7. Yellow dunes= highest, may form a ridge of marram grass near dune front
- not fully vegetated
-subject to alteration by wind & waves
8 Grey dunes= mature dunes
- the climax vegetation is either pine forest (where acidity is high) or oak forest (where shell deposits neutralise the soil a little)
70
What does uniform horizontal strata produce?
Steep cliffs
71
How are joints opened?
weathering & pressure release
72
