Coasts : PG Flashcards
1
Q
Define Coast.
A
A boundary zone where land and sea meet, and where both marine and terrestrial processes operate and interact.
2
Q
What is The littoral zone?
A
The wider coastal zone including adjacent land areas and shallow parts of the sea offshore.
3
Q
What qualities do Littoral Zones have?
A
- Exposed to air at low tide and underwater at high tide.
- Zone is divided into different sections.
- Back shore & foreshore areas are where physical processes and the greatest amount of human activity occur.
- Lots of coastal sediments (pebbles & sand particles)
- waves, current and tides move sediments around the zone.
- zones run from highest sea level line (high tide & storms) to the lowest sea level line (friction with sea bed) - 4 Zones: 1=foreshore 2=offshore 3=back shore 4=nearshore
4
Q
What are some examples of Natural Processes?
A
- Inputs of sediments from the sea from rivers flowing off land.
- Weathering
- Constructive & destructive waves
- Erosion
- Deposition
- Mass Movement
- Longshore Drift
- Tidal range
5
Q
What are some examples of Human Activities?
A
- Dredging in rivers
- Dredging offshore for sand
- The building of coastal defence — erosion & flooding
- Leisure activities
6
Q
What are Short term coastal change factors?
A
- Individual waves
- Daily tides
- Seasonal storms
7
Q
What are Long Term Coastal change factors?
A
- Changes to sea levels
- Climate change
8
Q
Why is the Coast a system?
A
- Constantly moving & changing
- Coastal systems have inputs, outputs & processes
- When inputs & outputs are balanced we can say they are in DYNAMIC EQUILLIBRIUM.
9
Q
What are some Examples of Inputs?
A
- Marine- waves, tides & storm surges.
- Atmospheric- weather/climate change & solar energy.
- Land- rock type, structure & tectonic activity.
- People- human activity & coastal management.
10
Q
What are some Examples of Processes?
A
- Weathering- wearing away of material.
- Mass Movement - movement of surface material.
- Erosion- wearing away of material.
- Transport- movement of sediment.
- Deposition- dropping off of sediment.
11
Q
What are some Examples of Output processes?
A
- Erosional landforms- arch, stack, stump, headland, bay.
- Depositional landforms- spits, tombolos, beaches.
- Different types of coasts- rocky shore, sandy beaches, coastal wetlands, coral reefs.
12
Q
Different types of Coasts: Rocky Coastlines.
A
- Cliffs of varying heights.
- Cliffs are formed from rock. The geology along the coastlines are particularly in relation to the hardness is very changeable.
13
Q
Example of a Rocky Coastline?
A
Boulby Cliffs, North Yorkshire.
14
Q
Different types of Coasts: Coastal Plains/Sandy Coastline
A
- Land slopes towards the sea across areas of deposited sediment.
- Find sand dunes & mudflats
- can also be called Alluvial coasts
- A low energy environment
- Less resistant geology
15
Q
Example of Coastal Plains?
A
Sand Dunes/banks, Swanage Bay Dorset.
16
Q
Different type of Coasts: Estuarine Coastlines.
A
- Found at the mouth of rivers.
- Deposition> erosion
- Low energy environment
- Area of Less resistant rock
17
Q
Example of Estuarine Coastlines?
A
Lymington Hampshire.
18
Q
What are the 5 different ways of Classifying Coasts?
A
- Tidal Range
- Geology
- Wave Energy
- Relative to sea level range
- Formation processes
19
Q
Classification of Coasts: Formation Processes.
A
- Primary Coasts: dominated by land based processes such as deposition at the coast from rivers or new coastal land formed from lava flows.
- Secondary Coasts: dominated by marine erosion or deposition processes.
20
Q
Classification of Coasts: Relative sea level change.
A
- Emergent coasts: where the coasts are rising relative to sea level, e.g. due to tectonic uplift.
- Submergent coasts: are being flooded by the sea, either due to rising sea levels and/or subsiding land.
21
Q
Classification of Coasts: Tidal Range.
A
Tidal range varies on coast lines:
- Microtidal= tidal range 0-2m
- Mesotidal= tidal range 2-4m
- Macrotidal= tidal range greater than 4m
22
Q
Classification of Coastal: Wave Energy.
A
- Low energy sheltered coasts with limited fetch and low wind speeds resulting in small waves.
- High energy exposed coasts, facing prevailing winds with long wave fetched resulting in powerful waves.
23
Q
The Wash + North Norfolk Beaches Sediment Supply.
A
- Sand is carried Southwards along the Lincolnshire Coast.
- The main source is from cliffs eroding between West Ruston and Weybourne, East of the Wash. These cliffs have retreated at around 1 meter per year for thousands of years.
- Some sediment comes from tidal currents, which pick up glacial deposits from the shallow sea floor.
- The erosion of the Holderness cliffs further north also produce some sediment.
- Sand is carried southwards along the Lincolnshire coast.
- The fact that sediment comes from different locations (north & east) illustrates what is known as sediment cells (11 in total).
24
Q
What is a High energy coastline?
A
- They have very powerful waves
- Rate of erosion > rate of deposition
25
Example of High energy Coastlines?
Stretches of the UK Atlantic - facing coastline
- Cornwall
- North-West Scotland
Erosional landforms, such as headlands, cliffs and shoreline platforms tend to be found here.
26
What are Low energy coastlines?
- Have less powerful waves.
- Rate of deposition > rate of erosion.
27
Examples of Low Energy Coastlines?
Stretches along the UK coasts where waves are less powerful
- Lincolnshire
- Norththumberland
Deposition landforms such as beaches, spits and coastal plains tend to be found in these environments.
28
Rock Type: Igneous
- The earths oldest rocks, formed in lavas and deep magmas
- These rocks were once molten, then cooled and crystallised
- Most of these rocks are resistant to erosion
- E.g Giants Causeway, Ireland.
29
Rock Type: Metamorphic
- These were originally sedimentary rocks by having been heated and compressed during igneous activity.
- Heating & Compression harden them and make them resistant — shale becomes slate & limestone becomes marble.
30
Rock Type: Sedimentary
- Formed from sediments eroded and deposited by rivers, the sea or sea beds.
- Some are resistant e.g limestone whilst others crumble easily e.g shale.
31
What is Offshore?
The area of deeper water beyond the point at which waves begin to break.
32
What is Nearshore?
The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distort the waves distort the wave sufficiently to cause it to break.
33
What is Foreshore?
The area between the high tide and low tide mark.
34
What is Backshore?
The area above the high tide mark, affected by wave action only during major storm events.
35
How do Coastal Plains form?
> They usually form by coastal accretion, where continuous net deposition causes the coastline to extend seawards.
> They also form by sea level change, when the falling sea level exposes a flat continental shelf.
36
What is a Concordant Coastline?
> Usually forms where rock strata runs parallel to the coastline.
> Long, narrow islands featuring
> Also known a Dalmatian coastlines.
37
What is a Discordant coastline?
> Where rock strata runs perpendicular to the coastline.
> Headland and Bay features
> Also known as Atlantic coasts
38
Example of a Concordant Coast.
South Dorset Coast.
> Resistant Portland Limestone
> Less resistant Purbeck Limestone and Wealding Clay
> eg Lulworth Cove
39
Example of Discordant Coastline.
Swanage Bay
> Formed from less resistant Carboniferous Limestone
> Sheep’s head Peninsula formed from more resistant coarse sandstone.
40
What are Joints?
Fractures in rocks created without displacement.
> Igneous rocks— form when magma contracts and looses heat.
>Sedimentary rocks— form when rock is subject to compression or stretching.
41
Example of a Jointing Place.
Stair Hole
> Purbeck Limestone is heavily jointed.
42
What is a Fault?
Makoy fractures in rock created by tectonic forces.
> Increase the rate of erosion
43
Example of a Faulting Place.
Bantry Bay
> The Carboniferous limestone is weakened by faulting.
44
What are Folds?
Bends in rocks. Produced by sedimentary rock layers being squeezed by tectonic forces.
45
What is a Dip?
The angle of inclination of the rock strata from the horizontal. Sedimentary rocks are deposited horizontally but can be tilted by folding and faulting.
46
How Lithology affects resistance: Mineral composition.
Some rocks contain reactive minerals easily Brocken down by chemical weathering.
47
How Lithology affects resistance: Rock class.
Sedimentary rock are very weak.
Igneous rocks are crystalline and strong
48
How Lithology affects resistance: Structure.
Rock with fissures or air spaces erode rapidly.
49
What is Rate of recession influenced by?
> How reactive minerals in rocks are when exposed to chemical weathering.
> Whether rocks are crystalline (more resistant) or clastic (less resistant)
50
What are Permeable rocks?
These are rocks that allow water to flow through them. Because:
1. They are porous
2. They have joints
51
What are Impermeable rocks?
Rocks that don’t allow water to flow through them
52
A spring creating erosion.
1. Where a permeable rock overlays an impermeable layer, groundwater is unable to percolate down into the lower layer.
2. Water accumulates in permeable layer, filling its pores with water.
3. Spring will form on the cliff face on top of saturated layer.
53
Groundwater flow removes cement.
Water flows through the permeable but can’t flow through impermeable so flows along the interface. Groundwater flows through the rock layers weakening the rock by removing the cement that binds it together.
54
Pore water pressure leads to slumping and sliding.
> Pore water pressure in the saturated layer pushes rock particles apart.
> Reduces friction between grains in unconsolidated material.
> Lubricates lines of weakness.
> Effects stability.
55
Saturation leads to slumping and sliding.
Saturation promotes mass movement through lubrication and by adding weight. Leads to slumping in unconsolidated material and sliding in consolidated — producing a complex cliff profile.
56
What does Wave size depend on?
- The strength of the wind
- The duration for which the wind blows
- Water depth
- Wave fetch
57
How does a wave break?
> When waves reach the shore, the internal orbital motion of water within the wave touches the sea bed.
> Friction between the sea bed begins to distort the wave particle orbit from circular to elliptical and slows down the wave
58
What are Constructive waves?
- Short wave height
- Long wave length
- Low wave frequency
- Strong swash, Weak Backwash
59
What are Destructive waves?
- High energy waves
- Large wave height
- Short wavelength
- High wave frequency
_ Strong back wash, weak swash
60
What is Beach Morphology?
The shape of the beach.
61
What is Decadal variation?
> Climate change is expected to produce more extreme weather events.
> More frequent and more powerful destructive waves may reduce beach size
62
What is Seasonal Variation?
Destructive, high energy waves dominate in the winter. Whilst constructive low energy waves dominate in summer.
63
What is Monthly Variation?
Tide height varies over course of lunar month, with highest high tide occurring twice a month at spring tide and two very low high tides (neap tides)
As month progresses from spring down to neap tide, successively lower high tides may produce a series of berms at lower and lower points down the beach.
64
What is Daily Variation?
Storms will produce destructive waves that can reshape the beach profile within a few hours.
Destructive waves change to constructive as wind drops.
65
What is Hydraulic Action?
Force of water hitting the cliff and squeezing air into the cracks in rock. Air forces the cracks to get bigger and eventually break small pieces of rocks away.
66
What is Abrasion?
Force of the bits of rock hitting each other and breaking into smaller rocks.
67
What is Attrition?
The process of rocks hitting each other and breaking into smaller rocks.
68
What is Solution/Corrosion?
A chemical reaction between the sea water and the minerals in the rock. Sea dissolves minerals and rocks begin to break up.
69
What is a Wave cut platform?
A curved intention of about 1-2m high extending along the base of a cliff. The depth of the notch depends on the resistance of the rock.
70
What are Headlands and Bays?
Protruding outing into the sea in the background with sandy bays between them.
71
Cave—Arch—Stack—Stump Sequence.
Rocks have joints, faults, or vertically, dipping, bedding planes in their geological structure, these are rated more rapidly forming a sea cave. A line of weakness extends through the headland cave, Marina erosion deepens this cave, creating a tunnel and forming an arch. Erosion Attacks. This further forming wave cut notches Material is aped forming an arch. Eventually, the roof of the arch will collapse, forming a stack. Once the stack has collapsed through erosion, a stump will form.
72
What is Traction?
Sediment rolls along pushed by waves and currents. E.G boulders, cobbles and pebbles.
73
What is Saltation?
Lighter sediment bounces along. Usually on a dry, windy day.
74
What is Suspension?
Where sediment is carried in a column of water. EG Holderness.
75
What is Solution?
Where dissolved minerals are carried in the water as a solution.
76
How do waves approach the beach?
True incoming swash transports the material up the beach at 90’ to the coastline. Backwash then transports sediment perpendicularly back down to the beach to its original starting position. Sediment travels up and down the beach in this way.
77
What is Longshore Drift?
When waves approach the coast at an angle. The incoming swash transports sediment up the beach at an angle. The gravitational backwash then transports the sediment back down at 90’.
78
What is Current?
This is the flow of water in a particular direction , they can transport sediment nearshore and offshore. Influenced by water density, temperature and salinity.
79
Depositional Landforms: Beaches.
Beaches are accumulations of sand or shingle in the foreshore and backs shore zones. Produced by material deposited by constructive waves. Swash has strength to carry material up the beach but backwash only has enough energy to transport some material back down.
80
What are Bayhead Beaches?
Bayhead beaches are curved beaches found at the back of a bay.
They’re common on swash-aligned coastlines where wave refraction disperses wave energy around the bay perimeter.
81
What are spits?
A Long narrow feature which extends from the land into the sea. Made of sand or shingle, which is moved along the coast by longshore drift, but suddenly the coastline changes direction then sediment will begin to be deposited and build up.
82
What are Offshore Bars?
Ridges of sand or shingle running parallel to the coast in an offshore zone. They form from sediment eroded by destructive waves and carried seawards by backwash.
83
What are Barrier Beaches?
Where the beach or spit extends across a bay to join two headlands up. Where the beach is separated from the mainlands it is referred to as a barrier island.
84
What is a Tombolo?
Linear ridge of sand and of shingle connecting an offshore island to the coastline of the mainland. Deposition occurs when the waves loose their energy and tombolos begin to build up. Can occur on swash aligned or drift aligned coastlines.
85
What is a Cuspate Foreland?
Low lying triangular shaped headlands, extending out from a shoreline, formed from deposited sediment. This occurs when a coast is exposed to longshore drift from opposite directions.
86
What is a Sediment Cell?
A linked system of sources, transfers and sinks of sediment along a section of a coastline.
> Operates as a closed system with no inputs or outputs of sediment from the cell.
87
Examples of Sediment Cells.
1. Flanborough Head
2. Holderness Coast
3. Spurn Head
88
What are inputs?
Places where sediment is generated, such as cliffs or eroding sand dunes.
89
What are transfers?
Places where sediment is moving along shore through longshore drift and offshore currents.
90
What are outputs?
Locations where depositional landforms are created.
91
What is a Dynamic System?
Sediment cells are dynamic because the sediment is constantly generated in the source region, transported through the transfer region and deposited in the sink region. Dynamic equilibrium is reached when inputs of sediment from the source region are balanced by the amount being deposited in sinks.
92
What is Negative Feedback?
When the change produced. Created effects that operate to reduce or work against the original change.
93
What is positive feedback?
When the changed produces an effect that operates to increase the original change.
94
What is Physical/ Mechanical Weathering?
The application of force to physically fragment rock into smaller pieces.
> Freeze Thaw: water seeps into cracks in rocks, when the water freezes it expands in volumes, this opens the faults more allowing more water to enter. Until repeated processes of thsi break the rock entirely.
95
What is Chemical Weathering?
Where chemical reactions attack individual minerals in the rock, forming chemical compounds.
> Carbonation, attacks calcium carbonate in limestones. Rainwater mixed with carbon dioxide from the air forms weak carbonic acid.
96
What is Biological Weathering?
When the break down of rock occurs through the interaction of it with living and non living organisms.
EG. Plant grows through a rock or animals scurrying repetitively over rock
97
What landforms can be created from Weathering?
1. Repeated freeze thaw can lead to scree slopes
2. Where eroded material/scree is built up a slope or cliff can be created
3. Rotational slumping will leaves marks on landscapes known as rotational scars,
98
What is Mass Movement?
The downslope movement of material under the force of gravity.
99
What is Rockfall?
Occurs on sloped where a rock fragment breaks away and drops. It is initiated by mechanical weathering and marine erosion.
100
What is Rotational Slumping?
Involves rock failure and movement along a curved rock plane. Occurs in weak rocks and unconsolidated material.
101
What are Landslides?
The downslope movement of discrete blocks of rock down a flat plane.
102
What is Eustatic change in sea level?
The change in global sea level, usually due to a change in the volume of water in the oceans. Rising water temperatures may lead to thermal expansion of water, increasing its volume even further.
1. Fall in sea level during the glacial periods whe ice sheets form on land in high latitudes.
2. Rise in sea level at the end of a glacial period, melting ice sheets return water to the sea and sea level rises globally. As temps increase the sea level rises.
103
What is Isostatic Changes?
A change in local land level.
1. Rises in local land level causes a fall in local sea level rise. Due to post glacial adjustments and accretion.
2. A fall in local land level produces a ride in local sea level. Due to post glacial adjustment and subsidence.
104
Eustatic in Tectonic events.
Rising magma reduces capacity of the ocean and produces Eustatic sea level rise.
105
Isostatic in Tectonics.
1. Folding of sedimentary rock by compressive forces at a destructive plate margin produces an Isostatic fall in sea level.
2. Lava or ask produces Isostatic fall
106
What are Emergent Coastlines?
A stretch along the coat that has been exposed by the sea by relative fall in sea levels.
107
What are Submergent Coastlines?
Stretches along the coast that have been flooded by the sea by a relative rise in sea levels.
108
Emergent: Raised Beach.
>A relict beach now above high tide level.
>A flat surface covered by sand or rounded pebbles
>Vegetated.
109
Emergent Coastlines: Fossil Cliffs
> A steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level.
110
Submergent: Fjord
> Drownded glacial valley
> Shallow entrance
> Relatively straight profile
111
Submergent: Rias.
> A drowned river valley
> Most common coastal landform
112
Past sea level change.
> Sea levels have risen by 125m since the Devensian Glacial
> Rate of sea level has increased since 1870
> Attributes this to global warming due to anthropogenic forcing greenhouse gas emissions.
113
Future sea level change.
> IPCC Predicts sea level rise of 18-59cm by 2100.
> Complete melting of Greenland ice sheet would raise global sea levels by 7m.
> Low lying coastlines and volcanoes at risk
114
What are Rocky Coastlines?
High relief, high energy, resistant rock and destructive waves.
115
What are Sandy Coastlines?
Low relief, low energy, low resistant rock, constructive waves.
116
What are Estuarine Coastlines?
Low relief, form at river mouths, low energy areas, less resistant rock.
117
What is a Swash aligned coast?
Waves approach parallel to the coast limited longshore drift.
118
What is a Drift aligned coast?
Waves approach at an angle consistent longshore drift.
119
What are the types of tide?
1. Spring Tide= highest monthly tide, twice a month.
Moon, sun and earth align.
2. Neap Tide= lowest monthly tide twice a month. Moon and sun at 90°
3. Tidal range= the difference in level between high and low tides.
