EQ2- Coasts Flashcards
1
Q
How are waves formed ?
A
formed by the gravitational pull of the moon acting on the earths surface
2
Q
What are tidal bores ?
A
waves capable of erosion
3
Q
what tide is the highest tide
A
spring tide
4
Q
how is a spring tide formed ?
A
When the sun and moons gravitational pull align in the same direction
5
Q
What 4 factors determine the strength of a wave ?
A
-Water depth
-strength of the wind
-duration of the wind
-fetch
6
Q
what are swell waves ?
A
Waves that have moved away from their generated area, with low steepness and a regular pattern
7
Q
how does water depth affect waves ?
A
Particles of water move in a circular motion. As waves approach the shore , friction with the sea bed slows the waves base. When water depth is half the wavelength, orbital motion creates more friction, decreasing wavelength and increasing wave height.
8
Q
what is wave shoaling ?
A
When wave slow down in shallow water, causing them to bunch together and increase in height.
9
Q
What is fetch ?
A
Fetch is the uninterpreted distance over which the wind can blow to form waves
10
Q
How does fetch affect waves ?
A
a longer fetch allows waves to gain more momentum and wave energy
11
Q
what do constructive waves do ?
A
They deposit sediment
12
Q
What is the form of a constructive waves ?
A
They have a strong swash, weak backwash, low height and long wavelength
13
Q
what do destructive waves do ?
A
They erode coastlines by removing sediment
14
Q
What is the form of a destructive wave ?
A
They have a weak swash, strong backwash, steep height, and short wavelength
15
Q
what is beach morphology ?
A
Beach morphology refers to the shape of the beach, including its width, slope, and features - it also includes the different types of sediment
16
Q
What are beach landforms ?
A
Beach landforms are physical features found on a beach, such as berms, storm beaches, runnels, and offshore ridges. These features change overtime due to wave action, tides and sediment movement
17
Q
What are the 6 beach landforms ?
A
-storm beaches
-berms
-offshore ridges
-beach cusps
-runnels
-drainage channels
18
Q
what is a storm beach ?
A
A very steep beach composed of varying sediment created by waves with a strong swash
19
Q
What are berms and how are they formed ?
A
similar to a storm beach but not as high, formed by deposition usually by summer swell waves
20
Q
What is an offshore ridge and how are they formed ?
A
An offshore ridge is a raised area of sand or shingle located parallel to the coastline. It is formed by destructive wave erosion and the subsequent deposition of sand and shingle offshore.
21
Q
What are beach cusps and how are they formed ?
A
Arc formations caused by backwash flowing back into the sea unevenly. The points of the cusp show the plae where the backwash is dragging the material with it
22
Q
What are runnels and how are they formed ?
A
Runnels are narrow toughs running parallel to the sea that trap water, they are formed due to the interaction of tides, currents, sediment and the beach topography
23
Q
What are drainage tunnels and how are they formed ?
A
Long, thin streams of water running perpendicular to the sea. The backwash carves these channels and runs back to the sea within them
24
Q
What are the 4 types of erosion ?
A
Hydraulic action, abrasion, corrosion and attrition
25
plunging destructive waves can exert a force of ..?
50kg/cm3
26
what are the two ways that hydraulic action can occur ?
Plunging destructive waves can break off material or weak rocks OR the force of breaking waves can compress air into cracks in rocks, forcing them apart
27
What waves make hydraulic action the most effective ?
High energy waves with a high wave height and a lack of debris at the cliff foot
28
How does debris affect hydraulic action ?
Debris at the cliff foot absorb energy from the waves, making hydraulic action less effective
29
How does abrasion occur ?
Waves pick up sediment and throw it against rocks, causing repeated impacts that chip away at the rock face
30
What types of waves make abrasion the most effective ?
High - energy destructive waves with a large wave height
31
What rocks erode the quickest due to abrasion ?
Soft sedimentary rocks such as chalk, mudstones and clays, and unconsolidated material
32
How does corrosion occur ?
Water from waves and seaspray dissolves rock minerals, which are carried away in solution
33
What type of waves are most effective for corrosion ? give a reason why
Constructive waves, as their spilling motion prolongs contact between water and rock allowing more time for chemical reactions
34
What types of rocks are most vulnerable to corrosion ?
Carbonate rocks (e.g chalk, jurassic limestone) and sedimentary rocks with calcite sediment or cement.
35
How does attrition occur ?
Rocks transported by waves collide with each other, breaking into smaller smoother fragments
36
Where does attrition mainly occur ?
In the foreshore and nearshore zones, where sediment is moved by swash and backwash
37
which types of rocks are mostly affected by attrition ?
Soft rocks like poorly cemented sandstones, chalk and clay, which break down into silt and sand grains
38
Is erosion a constant process ?
No, most erosion occurs during large storms rather than continuously
39
Erosion mostly occurs from what 5 situations ?
-When waves are at their largest (with the most energy)
-When waves approach a cliff at 90 degrees
-When the tide is high
- when there is heavy rainfall to weaken permeable rocks
-when previously eroded debris has been removed
40
What are the 4 erosional landforms ?
-Caves, arches, stacks ,stumps
-blow holes
-geos
-wave cut platforms
41
How do caves, arches, stacks and stumps form ?
Marine erosion widens cracks in rock, forming caves. Continued erosion breaks through to create arches. When arches collapse, stacks form, which erode into stumps
42
Where do caves, arches, stacks and tumps normally form ?
In horizontally bedded, medium - resistance sedimentary rocks
43
What is a blowhole and how does it form ?
When a cave is being eroded if there is a layer of weak strata or the presence of a fault line on the roof, the waves will erode this leaving a hole
44
What is a geo and how does it form ?
A narrow and deep split in the cliff face, formed due to marine erosion occurring along a line of structural weaknesses
45
How does a wave cut platform form ?
Hydraulic action and abrasion erode the cliff base between low and high tide, forming a notch. As erosion continues, the unsupported cliff collapses. Debris is removed by swash and backwash, and overtime compressed material forms a solid horizontal platform with a 5° gradient
46
What are the four types of transportation in coastal processes ?
Solution, suspension, saltation, traction
47
What is solution in coastal transportation ?
When soluble minerals, such as calcium carbonate are carried along any current as a solution
48
What is suspension in coastal transportation ?
When small particles such as clay and silt are carried and suspended in a weak current
49
What is saltation in coastal transportation ?
When sand-sized particles bounce and skip along the seabed under the energetic current
50
What is traction in coastal transportation ?
When larger pebbles, cobbles and boulders are rolled along the seabed only pushed by the strongest currents
51
What 4 factors influence sediment transportation ?
direction of wave attack, longshore drift, current and tides.
52
How does the direction of wave attack influence sediment transport ?
The direction of wave attack affects sediment movement, with swash transporting material up the beach and backwash moving it back down to the starting position.
53
How does longshore drift move sediment along the beach ?
Incoming swash moves sediment up the beach at an angle, and gravitational backwash transports it down at 90° to the coastline. Sediment moves in a zigzag pattern along the beach, with particles gradually coming to rest further along the shore
54
What wave angle causes the strongest longshore drift movement ?
30 degrees to the coastline
55
How do currents influence sediment transportation ?
Currents transportation sediment in nearshore and offshore zones, driven by wind, water density differences, temperature or salinity.
56
How do tides influence sediment transportation
Tides create tidal currents in the nearshore and offshore zones. moving sediment as they rise and fall due to the gravitational pull of the moon and sun
57
What are the two ways that sediment is deposited ?
Gravity settling, flocullation
58
What is gravity settling ?
When the energy of the transporting water becomes to low to move the sediment, causing it to settle
59
What is flocculation ?
When smaller particles, such as clay, clump together through electrical or chemical attraction and become havy enough to sink
60
What are the 6 depositional landforms ?
Spits, bars, offshore bars, tombolos, cuspate forelands, and beaches
61
How is a spit formed ?
When there is a change in direction of the coast material is still carried in the same direction. Due to the direction changing the sediment is now deposited out at sea, forming a spit. If the direction of the wind changes or wave refraction occurs this sill form a recurved spit.
62
How are bars formed ?
When a spit grows so long it extends across a bay closing it off
63
How are offshore bars formed ?
When waves approach a gently sloping coast, friction from the seabed causes waves to break at sea. This causes waves to lose energy and deposit any materials they are carrying, which causes an offshore bar to build up over time
64
What is a tombolo and how is it formed ?
A tombolo is a spit that connects the mainland to an island, formed through the same process as a spit.
65
How is a cuspate foreland formed ?
When longshore drift is operating at a coastline that changes direction. This causes the creation of two spits that meet and create a triangular shape
66
How are beaches formed ?
By material deposited by constructive waves as the backwash cannot carry all material deposited by the swash, leaving some material forming a beach
67
What can stabilise depositional landforms ?
Plant succession
68
What is a sediment cell ?
A closed system that indicates sediment movement along a coastline
69
How many main sediment cells ere there in the uk ?
11 main sediment cells
70
What physical feature helps define sediment cell boundaries ?
The coastlines topography, especially peninsulas
71
Why do peninsulas help define sediment cells ?
They block sediment movement between cells
72
What are sources in a sediment cell ?
Places where sediment originates
73
Give three examples of sediment sources within a sediment cell
Cliffs, offshore bars, and rivers
74
Some sources can also be ... ?
sinks
75
What are the 4 main types of mass movement ?
-Slumping
-landslides
- rockfall
-mudflow
76
Give three examples of sediment sinks within a sediment cell
Sand dunes, spits and offshore bars
77
How can an offshore bar be both a source and a sink ?
Depends on wether constructive or destructive waves are present
78
What is the roles of transfers in a sediment cell ?
They move a sediment from a source to a sink
79
Why is the theory of sediment cells useful ?
It helps predict coastal erosion and manage coastal defences
80
What are sinks in a sediment cell ?
Places where deposition is the dominant process
81
What is slumping ?
Slumping occurs when waves erode the base of a cliff made of boulder clay and soil, causing the saturated cliff to slump across a slip plane due to gravity
82
Where does slumping occur ?
In weak rocks, unconsolidated material and in rocks with complex geology
83
How do landslides occur ?
Occurs in areas of resistant rock where waves erode the base of a cliff. As the size of the wave-cut notch increases so does the instability of the cliff as the weight cannot be supported causing a landslide
84
Where do landslides occur ?
In consolidated rocks with joints or bedding planes that slope seawards
85
How does rockfall occur ?
Rockfall occurs when fragments of rock break off a cliff, often due to freeze-thaw weathering
86
Where does rockfall occur ?
Cliffs with many joints, faults or bedding planes that have a steep or near vertical dip of strata and are also im earthquake-prone areas
87
How does mudflow occur ?
When saturated soil and weak rocks flow down a slope
88
What is an example of a rockfall mass movement event ?
St. Oswald's bay
89
What type of rockfall occur at in the st.oswalds bay rockfall ?
cretaceous rock fall
90
How large was the section of cliff that collapsed at st. oswald's bay ?
80 - 100m
91
The rockfall occured overnight without... ?
warning
92
What are the 3 landforms created by mass movement ?
-scree slope
-Terraced cliff profile
--back scar/rotational cliff
93
What is a scree slope ?
A large slope of material left due to the formation of a wave-cut notch or from rock fall
94
What causes a terraced cliff profile ?
Caused by slumping, where sections of the cliff move downward. creating horizontal layers
95
What is a back scar or rotational scar ?
Formed by slumping and is the exposed surface of a cliff where material has moved down and rotated, leaving a scar
96
What 3 features of geological structure can affect mass movement ?
Presence of joints, low angle seaward dip, landward dip
97
How does the presence of joints affect mass movement ?
Joints create weaknesses in rocks, making rockfalls more likely as marine erosion exploits them
98
How does a low angle seaward dip affect mass movement ?
A low angle seaward dip make rockfalls more likely due to erosion weakening cliffs and causing rock strata to become more unstable
99
How does a landward dip affect mass movement ?
It prevents rockfalls and rock topples but increases the likelihood of a landslide
100
What are the 3 main types of weathering ?
Mechanical, biological and chemical
101
What are the two different types of mechanical weathering ?
Freeze thaw and salt crystallization
102
How does freeze thaw weathering occur ?
Water expands by 9% when frozen, exerting force within cracks and fissures, which can cause rocks to crack and break apart
103
What types of rocks are vulnerable to freeze thaw weathering ?
Rocks with cracks and fissures, especially those high on cliffs away from salt spray
104
How does salt crystallization occur ?
The growth of salt crystals in cracks and pore spaces can exert a breaking force in cracks and pores
105
What rocks are more vulnerable to salt crystallization ?
Rocks with many pores or cracks, particularly those in hot climates where salt crystals can form due to evaporation and precipitation
106
What are the three types of chemical weathering ?
Carbonation, Hydrolisis, oxidation
107
How does carbonation weather rocks ?
Carbon dioxide dissolves in rainwater to form carbonic acid, which reacts with calcium carbonate in limestone to form calcium bicarbonate, gradually weathering the rock
108
What rocks are most vulnerable to carbonation ?
All carbonate rocks
109
What happens. during hydrolysis in weathering ?
Water reacts with minerals in rocks, causing chemical changes that create new clay minerals and make the rock unstable
110
What rocks are vulnerable to hydrolysis ?
Rocks that contain feldspar or other silicate minerals
111
How does oxidation weather rocks ?
Oxygen reacts with minerals, particularly iron compounds, leading to the formation of iron oxides, which increases volume and contributes to mecahnical weathering
112
What rocks are most vulnerable to oxidation ?
Rocks containing iron, such as sandstones and siltstones
113
What are the two types of biological weathering ?
Plant roots and rock boring
114
How do plants contribute to weathering ?
Trees and plant roots can grow in cracks and fissures, forcing rocks apart
115
What rocks are vulnerable to plant root weathering ?
All rocks with cracks and fissures, especially those near vegetated areas or cliff tops
116
How does rock boring weather rocks ?
Many species of clams and molluscs bore into rock, they may also secrete chemicals that dissolve rocks
117
What rocks are most vulnerable to rock boring ?
Sedimentary rocks, particularly carbonate rocks like limestone, found in the inter tidal zone
