Coasts: How do characteristic coastal landforms contribute to coastal landscapes EQ2 Flashcards
(70 cards)
1
Q
What are waves caused by?
A
Friction between wind & water with some energy from the wind being transferred into the water
2
Q
What 3 factors does wave size/energy depend on?
A
- strength of wind - stronger wind= more powerful when they break on the shore
- duration - how long wind blows for
- wave fetch - distance of open water the wind blows over (further wave can travel uninterrupted= more powerful it will be when it reaches the shore)
3
Q
What are the two types of waves?
A
Destructive & constructive waves
4
Q
Constructive waves:
- what energy waves are they?
- what type of wave height do they have? (give an example)
- what type of wavelength do they have? (give an example)
- what type of swash do they have? and what does it do?
- what type of backwash do they have?
- How to describe the wave= wave ‘?’
- what type of beach is produced?
A
- low energy wave
- low, flat wave height (less than 1m)
- long wavelength (up to 100 m)
- strong swash= pushes sediment up beach depositing it as a ridge of sediment (berm) at top of beach
- weak backwash= deposition occurs on beach
- wave ‘spills’
- build up the beach with a gentle beach profile
5
Q
Destructive waves:
- what energy waves are they?
- what type of wave height do they have? (give an example)
- what type of wavelength do they have? (give an example)
- what type of swash do they have? and what does it do?
- what type of backwash do they have?
- How to describe the wave= wave ‘?’
- what type of beach is produced?
A
- high energy wave
- large wave height (over 1 m)
- short wavelength (around 20 m)
- weak swash
- strong backwash= erodes beach material and carried it away from beach creating an offshore ridge or bar
- wave ‘plunges’
- beach is limited, with s teeper beach profile
6
Q
What does beach morphology refer to?
- what things are included in this?
A
The shape of the beach
- width & slope (beach profile)
- features like berms and ridges
- type of sediment (single, sand, mud) found at different locations on the beach
7
Q
Beach profiles:
- what does this refer to?
what can different wave conditions do?
A
- the pattern of distribution of different sized or shaped deposited material
- change the landforms of beaches
8
Q
What are beaches formed from?
- and what do waves alter on a beach?
A
loose material
- waves alter morphology (form & shape) of the beach
9
Q
what else is morphology affected by?
A
size & shape of beach material
10
Q
What can the type of wave in an area depend on? (give an example)
A
- time of year
- coastal management
e.g.
beach profiles steeper in summer= fewer destructive waves (less backwash)
gentler in winter= more constructive waves (more swash)
11
Q
What are the 4 marine erosion processes?
A
- Hydraulic action
- Corrosion
- Abrasion
- Attrition
12
Q
What 3 factors can affect marine erosion?
A
- wave type (constructive/destructive)
- wave size (fetch & direction)
- lithology
13
Q
How can wave type & wave size affect erosion?
A
- affects the seasonal changes in the amount of erosion
- erosion tends to happen more during winter= greater number of destructive waves
- size and type of waves affects amount of hydraulic action and abrasion
14
Q
How can lithology affect erosion?
A
- lithology influences rate of erosion
- weaknesses in rocks= erode more quickly
- more resistant rocks= erode more slowly
15
Q
What is hydraulic action?
A
the shear force of the waves force air at high pressure into cracks in the cliff, over time this weakens the rock and causes the joint to widen
16
Q
What is corrosion?
A
weak acids in seawater dissolve the rock particles
17
Q
What is Abrasion?
A
sediment and stones picked up by waves and wear away at cliffs/headland
18
Q
What is attrition?
A
as rocks are moved around by the water they knock into each other gradually becoming smaller and rounder
19
Q
What does a bigger beach mean?
A
More energy it can absorb before the waves reach the backshore/cliffs causing erosion
20
Q
What rock types will lead to more erosion?
A
Sedimentary
21
Q
What rock types will lead to less reosion?
A
Igneous & metamorphic
22
Q
What is the effectiveness of marine erosion processes determined by?
(5 things)
A
- The type of wave (destructive or constructive)
- The size of wave (linked to energy)
- The tide level
- The shape of the coastline
- The lithology (characteristics of the rock)
23
Q
How does the type of wave influence marine erosion processes?
A
Destructive= hurls material at a greater force into cliffs resulting in faster rates of erosion by abrasion
24
Q
What marine erosion process is most effective? why?
- what rocks are eroded more quickly by abrasion?
A
Abrasion
- soft sedimentary rock such as chalk and clays
25
What does erosion create?
Distinctive coastal landforms
26
Name the Landforms of coastal erosion
1. wave-cut notch
2. wave-cut platform
3. cliffs
4. caves, arches, stacks and stumps
27
How are wave-cut notches created?
1. At high tide, destructive waves break on to base of cliff
2. The processes of abrasion & hydraulic action wear away at rock
3. A curved, wave cut notch forms along length of cliff, with variations depending on resistance of rock
4. Weaker points= sea caves will form
28
How are wave-cut platforms created?
1. As a cliff is eroded at its base, the rock above is left unsupported
2. It eventually collapses under the influence of gravity
3. The cliff retreats (recession) leaving behind a flat/slightly sloping area of rock between high-tide and low-tide levels where the land used to be
4. Not just the result of wave action but also weathering processes
29
How are cliffs created?
1. Either vertical or near-vertical slopes caused by waves undercutting land at high tide or constantly if there is no beach
2. As cliffs are undercut, gravity causes mass movement in the unsupported rock
3. Cliffs exist in both more/less resistant rocks so type of mass movement depends on geology
30
What does mass movement depend on?
Geology
31
How are caves, arches, stacks and stumps created?
1. At a headland waves will refract= full energy of erosion processes concentrated on weak points on the sides
2. Hydraulic action & abrasion come first to form caves which can meet at opposite ends to form a tunnel= rock arch
3. As arch becomes more prominent + further erosion and weathering the top eventually collapses, leaving a pillar of rock= stack at the seaward end of a headland
4. waves continue to erode base of stack cutting notches in several sides
5. The stack then becomes unstable & collapses leaving just the base= stump (visible at low tide, submerged at high tide)
32
What do various transport processes do?
Move sediments along coastlines
33
Where do waves move sediment?
Up and down beaches
34
Where to rip current transport sediment?
From foreshore to nearshore areas
35
Longshore-drift:
- when does the longest LSD occur?
- what is the forward movement called & what does it do?
- what is the backward movement called & what does it do?
- when do sediments finally stop moving up the beach in a zigzag pattern?
- when waves approach the coast at at a 30 degree angle to the beach
- swash= moves beach sediment up beach at same angle as wave approaches
- backwash= carries beach sediment back down beach at right angles to the shore, under influence of gravity
- when they reach a natural barrier (a bay or estuary) or an artificial barrier (a groyne)
36
What are the 4 sediment transport processes?
1. Tracion
2. Saltation
3. Suspension
4. Solution
37
Traction
Large and heavy rocks dragged along seabed
38
Saltation
Smaller and lighter rocks which can be lifted by the water, bounce along seabed
39
Suspension
Lighter material carried in suspension
40
Solution
Dissolved sediment carried in solution
41
Name the Landforms of coastal transportation and deposition
1. Beaches
2. Offshore bar
3. Barrier beaches
4. Nearshore bars
5. spit
6. Tombolo
7. Cuspate foreland
42
Spits form when? (3 things)
- what moves the sediment?
- what happens overtime?
- what do spits shelter?
- what eventually grows and forms in the area?
- what happens as the spit grows longer & why?
- there is a dominant main longshore drift direction
- there are plenty of sediments from mass movement & erosion
- there is a gap in the coastline= e.g. estuary or bay
- LSD carries sediments along coast until they reach a gap in the coastline= then deposited on seabed
- Overtime the material breaks through the surface of the sea= forms narrow strip of land across part of the bay or estuary
- shelters the area of seawater behind it so sediments from sea are deposited in the calm area
- eventually salt-tolerant plants grow to form mudflats and a salt marsh
- Secondary wind, wave direction, tides and river currents= turn end of spit into a hook (recurved spit)
43
What is a salt marsh?
A coastal wetland dominated by salt-tolerant plants, like grasses, that are regularly flooded and drained by tides
44
What 2 things cause a double spit to occur?
(give a real life example)
When there are local variations of longshore drift and a large bay with strong river currents
e.g. Poole Harbour, Dorset
45
How does a tombolo form?
After LSD carries sediments across a gap between the mainland & an island, forming a narrow ridge of sand and pebbles.
46
What is a cuspate foreland?
An open landscapes with parallel ridges of shingle and sand, marking the stages in the formation of a spit and the foreland
47
How are cuspate-forelands formed?
A low-lying headland
- formed when significant LSD is from opposite directions along a coast, so sand and pebbles are deposited across a bay from both directions, forming two spits
- eventually the two spits meet and shelter the area behind in the bay
- further coastal deposition causes the bay to fill up with sediment
- mudflats and salt marshes form and the deposition will eventually be enough to form a new area of lowland
Open landscapes with parallel ridges of shingle and sand, marking the stages in the formation of a spit and the foreland
48
Are sediment cells considered an open or closed system? and why?
Closed - as most sediment movement is contained within the cell
49
What can sediment cells be divided into? and what can be found here
Sub-cells - where the sources, transfers and sinks are found
50
Give an example of a flow diagram of a source, sink and transfer in a sediment cell
Erosion in one place (source) - will be balanced by deposition in another place (sink) - and LSD and currents transfer sediment within the cell (transfer)
51
What is the sediment budget?
- what should the sediment budget be like in a coastal system?
- what can disrupt this state?
The balance between the inputs and outputs of sediment in the system
- In a state of dynamic equilibrium
- human activity & natural changes (e.g. climate change) can disrupt the state of dynamic equilibrium
52
What do both positive & negative feedback do for a sediment cell?
(Give an example of both)
PF= change the balance until a new equilibrium is reached
e.g. damage to sand dunes during storm= may create 'blow-out'= allowing wind to move more sand away= prevents grasses from growing= allows for further erosion
NF= helps maintain a balance within a system
e.g. wave erosion causes rock falls= then protects base of cliff from further erosion
53
What 2 things can the sediment budget be useful in assessing?
1. coastal change
2. The effect of coast management schemes
54
Sources in a sediment cell
- erosion of cliffs
- onshore currents supplying sediments to shore
- land sediment eroded by rivers
- wind blown (aeolian) sediments from land
- subaerial processes (weathering & mass movement)
55
Transfers in a sediment cell
- Longshore drift
- Wave transport through swash & backwash
- tides moving sediments in and out
- currents e.g. rips
- wind
56
Sinks in a sediment cell
- Backshore depositional landforms
e.g. sand dunes
- Foreshore depositional landforms
e.g. beaches
- Nearshore depositional landforms
e.g. bars
57
What are the 2 subaerial processes?
- what do they alter?
Weathering & mass movement
- alter the shape of a coastline
58
Landforms of coastal mass movement case study example?
Happisburgh, North Norfolk
59
What is weathering?
The breakdown of rock in its place or origin
60
What are the 3 different types of weathering? describe each one
Mechanical (Physical) - when rocks break down, with no chemical changes
Biological - rock breaks down due to organic activity
Chemical - rock breaks down due to a chemical reaction - rock changes
61
Mechanical (physical) weathering: Name & describe two
Freeze-thaw weathering
- only happens in places where temp changes daily above and below zero
1. water seeps into joints & cracks in rock
2. when it freezes it expands exerting pressure & forcing rock to crack
Salt crystallisation
- occurs bc salt crystals are bigger than water molecules
1. water collects in the cracks in the rock when it rains
2. when the sun shines, water evaporates, salt crystals are left behind in the cracks
3. salt crystals grow over time & create stress on rock causing it to break up
62
Chemical weathering: Name & describe one
Oxidation
- when iron minerals in the rock react with oxygen in the air to cause rust and breakdown the rock
63
What is mass movement?
The downslope movement of material under the influence of gravity
64
What 2 things cause a slope/cliff to become unstable & increase likelihood of mass movement?
1. After waves have undercut resistant rocks
2. When rainwater enters unconsolidated rocks and forces particles apart
65
What are the 3 types of mass movement?
Blockfall, rotational slumping, landslides
66
What determines the TYPE of mass movement?
Water content
67
What factor determines the stability of a slope/cliff?
The slope angle
68
What else makes cliffs more vulnerable to weathering? (geology)
- what does this contribute to & eventually result in?
Strata
- contributing to formation of wave-cut notches= resulting in mass movement
69
Blockfall:
- what is it?
- where do they occur?
- what can happen to blocks of rock on a coast?
- how can this lead to large falls?
- what type of landform does this create?
- Rapid form of mass movement
- occur on steep slopes
- can be dislodged by mechanical weathering or hydraulic action
- wave erosion creates a wave-cut notch= cliff no longer supported
- Talus scree slope
70
Rotational slumping:
- what is it?
- what does this leave?
- what will a sequences of slumps cause?
- where a section of a cliff remains intact as it moves down a cliff along a curved slip plane
- leaves a crescent-shaped rotational scar above it on the cliff
- terraced cliff profiles
