1
Q
What is the littoral zone?
A
A zone that stretches out in to sea and on to the shore and is constantly changing. It is divided in to 5 parts: coast, backshore, foreshore, nearshore, offshore.
2
Q
What is the dynamic equilibrium?
A
Where the inputs and the outputs are balanced as changes are counteracted.
3
Q
Define offshore.
A
Far out to sea
4
Q
Define nearshore.
A
Closer to the shore but still deep water.
5
Q
Define foreshore.
A
Shallow sea e.g where you can paddle.
6
Q
Define backshore.
A
Usually above the influence of the waves.
7
Q
What factors effect the littoral zone?
A
Short-term- individual waves, daily tides, seasonal storms.
Long term- sea level and climate change
8
Q
What are some inputs of the coast?
A
- Waves
- Tides
- Storm surges
- Rock type
9
Q
What are some processes of the coast?
A
- Weathering
- Mass movement
- Deposition and transportation
10
Q
What are some outputs of the coast?
A
- Types of coasts
- Depositional and erosional landforms.
11
Q
What are the features of a coastal plain?
A
- Coastal plain landscapes are relatively flat, low-relief areas adjacent to the sea.
- They often contain freshwater wetlands and marshes due to the poor drainage of the flat landscape.
- Their littoral zone is composed of sand dunes, beaches, mud flats and salt marshes.
- Coastal plain landscapes form in low-energy environments where deposition > erosion, so they experience a net accumulation of sediment. They form through coastal accretion (a continuous net deposition of sediment.) This comes from:
- Offshore sources (transported by waves, tides or currents)
- Terrestrial sources (transported by rivers, glaciers, wind or mass movement)
- Coastal plains may be sandy coasts, composed of sands, shingles and cobbles.
- Estuarine (alluvial) coasts composed of mud (clays and silts)
They form most of the UK’s south and east coastline.
12
Q
What is the formation of a coastal plain?
A
- They usually form by coastal accretion, where continuous net deposition causes the coastline to extend seawards. This is often extended biologically as plants colonise shallow water, trapping sediment and forming organic deposits when they die.
- They also form by sea level change, when the falling sea level exposes a flat continental shelf. e.g. the Atlantic coastline of the USA.
- Where erosion = deposition dynamic equilibrium exists as there’s a continuous flow of energy and material through the coasts, but the size of stores (beach, salt marsh, mudflat) remains unchanged.
13
Q
What are the features of a rocky coast?
A
- Rocky coasts occupy about 1,000 km of the UK’s coastline, mainly in the north and west.
Cliffs vary in height from high-relief areas, - e.g. 427 m Conachair Cliff on the Isle of Hirta in the Outer Hebrides
- To low-relief
- e.g. 3m cliffs at Chapel Porth in Cornwall
- Rocky coasts usually form in areas of geology that are resistant to the erosive forces of the sea, rain and wind. Their lithology and structure mean they erode and weather slowly
14
Q
What are the characteristics of high-energy coasts?
A
- Destructive waves
- Largest waves
- Erosion
15
Q
What are the characteristics of low-energy coasts?
A
- Constructive waves
- Deposition
- Forms beaches, spits
16
Q
What are constructive waves?
A
- Low energy waves.
- Low, flat wave height (<1m).
- Long wavelength (up to 100 m).
- Low wave frequency (about 6-9 per minute).
- This means their swash is unimpeded by the previous backwash.
- A strong swash pushes sediment up the beach, but a weaker backwash is unable to transport all particles back down, so they have deposited it as a ridge of sediment (berm) at the top of the beach.
- A backwash that percolates into the beach material.
encouraged by a long, shallow nearshore, so friction slows down the wave and releases energy - Constructive (spilling or surging) waves have a stronger swash than backwash due to a low angle of wave impact.
17
Q
What are destructive waves?
A
- High energy waves.
- Large wave height (>1 m).
- Short wavelength (about 20 m).
- High wave frequency (13-15 per minute).
- They’re encouraged by a short, steep nearshore zone, quickly dropping away into deeper water, so that there is little energy loss through friction.
- They have strong backwash and weak swash due to the steep angle of impact.
- This directs most energy downwards and backwards, so the particle orbit is more circular than constructive breakers(?).
- Strong backwash erodes material from the top of the beach, carrying it down the beach to the offshore zone.
- It’s often deposited as an offshore ridge or berm.
18
Q
How do constructive waves alter the beach morphology?
A
- Constructive waves alter beach morphology by causing net movement of sediment up the beach, steeping the beach profile.
- They produce berms at the point where the swash reaches the high tide line. (A berm is a ridge of material across the beach).
- Swash carries sediment of all sizes up the beach, but weaker backwash can only transport smaller particles down the beach.
- This leads to the sorting of material in the foreshore zone, with larger, heavier shingles (pebble-sized sediment) at the back of the beach, and sand is drawn back closer to the sea.
Since the backwash flows down the beach and loses energy through friction and depletion of water through percolation, sediment is further sorted as coarser sands are deposited in the middle of the beach and only fine sands are carried to the area of the beach closest to the sea.
19
Q
How do destructive waves alter the beach morphology?
A
- Weak swash and powerful backwash produce a net transport of sediment down the beach, reducing beach gradient.
- Some sediment is thrown forwards in a detached spray of high-impact breaking waves. Accumulates above the high tide mark as a storm ridge.
- Large, pebble-sized sediment dragged down the beach by backwash to form a wide ridge of material below the low tide mark at the start of the offshore zone.
- Friction may be sufficient to cause backwash to down some sediment on the middle or lower beach, with deposited sediment size decreasing towards the sea.
20
Q
How does decadal variation alter beach morphology?
A
- Climate change is expected to produce more extreme weather events in the UK.
- Winter profiles may be present for a longer time over course of the year.
- More frequent and more powerful destructive waves may reduce beach size, allowing high tides to reach further inland and increasing the rate of coastal erosion in what was the backshore zone.
21
Q
How does seasonal variation in the UK alter beach morphology?
A
- Destructive, high-energy waves dominate in the winter, lowering the angle of the beach profile and spreading shingles over the whole beach. Offshore ridges/bars formed by destructive wave erosion and subsequent deposition of sand and shingle offshore.
- In summer, constructive, low-energy waves dominate, steepening the beach angle and sorting particles by size, with larger shingle particles towards the back of the beach. In summer, constructive waves build berm ridges, typically of gravel/shingle at the high tide mark.
-Low channels and runnels between berms.
22
Q
How does monthly variation alter beach morphology?
A
- Tide height varies over course of the lunar month, with the highest high tide occurring twice a month at spring tide and two very low high tides (neap tides).
- As the 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.
- Once the neap tide passes and moves towards the next spring tide, berms are successively destroyed as a material is pushed further up the beach by rising swash reach.
23
Q
How does daily variation alter beach morphology?
A
- Storm events during summer will produce destructive waves that reshape the beach profile in a few hours.
- Calm anticyclonic conditions in winter can produce constructive waves that begin to rebuild the beach, steepening the profile for a few days before the storm.
- Destructive waves change to constructive ones as the wind drops.
- Storm beaches, high at the back of the beach, resulting from high energy deposition of very coarse sediment during the most severe storms.
24
Q
The energy transferred by the wind depends upon:
A
1. wind strength
2. wind fetch
- (the uninterrupted distance of open water over which the wind blows)
- a larger fetch allows the wind to push against the water for a longer time, transferring more energy
- wind duration
- the longer the wind blows, the more energy it transfers
25
What are sea waves and swell waves?
- Sea waves are produced by winds currently blowing in the local area and vary in height and direction.
- When the wind drops, wave energy continues to be transferred across the ocean in the form of swell waves.
- As swell waves travel away from their origin they may absorb smaller sea waves and gain energy and height.
- They can travel long distances before they lose energy and dissipate.
- They produce waves on the coast even when there is no wind.
- Swell waves can form periodically larger waves amongst smaller, local sea waves at the coast.
26
How are igneous rocks formed?
Created by volcanic activity where magma or lava cools forming hard crystals that are usually hard. e.g granite and bassalt
27
How are metamorphic rocks formed?
Formed by extreme heat and pressure, usually form bands of crystals and very hard. e.g marble
28
How are sedimentary rocks formed?
Formed of small particles that have been eroded, transported and deposited into layers or form from the remains of plants or animals. e.g limestone, chalk
29
Where in the UK are metamorphic rocks found?
North
30
What is coastal morphology?
Shape and form of coastal landscapes and their features.
31
What is wave reflection?
Is the bending of a wave due to its interaction with the seabeds topography and/or shape of the coastline.
32
What is coastal recession?
Another word for coastal erosion.
33
What is lithology?
Physical characteristics of rocks.
34
What are strata?
Layers of rock.
35
What are bedding planes?
Horizontal cracks in the rock. Natural breaks in the strata.
36
What are joints?
Vertical cracks are caused by contraction as sediments dry out.
37
What are folds?
Formed by pressure during tectonic activity which makes rocks crumble.
38
What are faults?
Formed when the stress or pressure to which a rock is subjected to.
39
What is a dip?
Refers to the angle at which the strata lie.
40
What are the six phases that occur due to geological structure that link to cliff profiles.
1. Horizontal dip: Steep profiles of 70/80 degrees produces a very stable cliff with reduced rockfalls.
2. Seaward dip, High angle: Vertical or near vertical profile with notches reflecting strata that are more easily eroded through weathering.
3. Seaward dip, low angle: Sloping, low angle profile. Causes rock falls.
4. Landward dip: Produces stable cliffs with reduced block fall and a steep profile.
41
What are micro features?
- Micro-features are small-scale coastal features such as caves and wave-cut notches which form part of a cliff profile.
- They form in areas weakened by heavy jointing, which have faster rates of erosion, enlarging the joint to form a sea cave.
- The location of micro-features found within cliffs, is often controlled by the location of faults and/or strata which have a particularly high density of joints and fissures.
42
How are complex cliff profiles formed?
- Complex cliff profiles are produced where cliffs are composed of strata of differing lithology. Less resistant strata erode and weather quickly, being cut back rapidly, wave cut notches may be formed. Resistant strata erode and weather slowly, retreating less rapidly. They may form a 'bench' feature at the cliff base. Higher up, they form overhanging sections until they collapse by a mass movement. However, generally, the overall rate of cliff recession is determined by the resistance of its weakest rock layer.
- Rocks show different levels of resistance to marine erosion in the foreshore zone.
- Rocks show different levels of resistance to weathering or mass movement in the foreshore and backshore zones.
43
How can cliff profiles be produced when there are alternating permeable and non-permeable strata?
- Permeable rocks are those that allow water to flow through them. This may be because:
- They're porous (e.g. chalk)
- These are rocks containing voids called pores, for example, chalk and poorly cemented sandstones
they have numerous joints (e.g. carboniferous limestone).
- Examples of permeable rocks are many sandstones and limestones.
Permeable rocks tend to be less resistant to weathering because water percolating comes into contact with a large surface area that can be chemically weathered.
- e.g. Limestone weathered by carbonation converting calcium carbonate to soluble calcium bicarbonate.
- Feldspar in granite weathered by hydrolysis into kaolin (china clay).
- Impermeable rocks do not allow water to flow through them.
- Clays, mudstones, and most igneous and metamorphic rocks are impermeable.
44
What are the 4 ways in which cliff profiles are produced due to alternating permeable and non-permeable strata?
1) A spring creating erosion
2) Groundwater flow removing cement
3) Pore water pressure leads to slumping and sliding
4) Saturation leads to slumping and sliding
45
What are the two types of cliff profiles?
- There are two main types of cliff profiles:
Steep, unvegetated cliffs:
- Produced where marine erosion dominates
- There is little or no debris at the base because it is broken up by attrition and transported offshore or along the coast.
Shallow-angled, vegetated cliffs:
- They have a convex profile (convex = curved like the interior of a circle).
- There is debris at the base.
- Because sub-aerial processes (weathering, mass movement and surface run-off erosion) slowly move sediment downslope, marine erosion is unable to remove it from the base.
- Produced where there is little active marine erosion.
46
How do geology and lithology affect the coastline?
Igneous rock:
- Very resistant. Annual recession is 1mm per year.
- Impermeable with very few spaces or joints
- Few strata
Metamorphic rock:
- Very resistant. Impermeable with very few spaces of joints for water to pass through.
- 0.1-0.3cm a year erosion
Sedimentary:
- Thinly bedded. Annual recession is 2.5cm per year.
- Often porus- makes it susceptible to weather.
- Have weak bedding planes
Unconsolidated material:
- 1m per year is an annual recession. loose material and so permeable.
47
What is the difference between a concordant and discordant coastline?
Concordant coast is where bands of hard and soft rock run parallel to the coast. Discordant coasts are where layers of hard and soft rock run at right angles to the coast.
48
What's a haff coastline?
Type of concordant coastline. Long ridges of sand and mud run parallel to the shoreline with lagoons behind them.
49
What's a Dalmatian coastline?
Valley and ridges run parallel to eachother. When the valleys are flooded, tops of ridges remain above the surface.
50
What are salt marshes?
Areas where flat silty sediments accumulate around estuaries or lagoons.
51
How do salt marshes develop?
- In sheltered areas where deposition occurs.
- Where salt and fresh water meet.
- Where theres no strong tides or winds.
52
What are halophytes?
Plants that are adapted to salty conditions and the dry conditions.
53
How does vegetation stabilise the coast.
They stabilise the coast through sand dune succession and salt marsh succession.
- In addition, vegetation increases the rate of sediment accumulation:
1. Plant stems and leaves interrupt the flow of wind and water, reducing their velocity and encouraging deposition.
2. When the vegetation dies it adds its organic matter (hummus) to the soil.
Pioneer species:
- These are the first plants to colonise freshly deposited sediment.
They modify the environment:
- Stabilising sediment
- Adding organic matter that retains moisture, contributes nutrients and provides shade.
- Reduce evaporation in the sand.
Sand dune succession:
- Embryo dunes form when seaweed driftwood or litter provides a barrier or shelter to trap sand.
- As the embryo grows, it is colonised by xerophytic pioneer plants, like sea couch grass, lyme grass, saltwort and sea rocket.
- Pioneer plants stabilise the sand allowing marram grass to colonise.
Marram grass is marvellous because of it:
- Has waxy leaves to limit water loss through transpiration and resist wind-blown sand abrasion.
- Has roots that can grow to 3m to reach down the water table and the stem can grow 1m a year to avoid burial by deposited sand.
- Allows the dune to grow, rapidly forming a yellow dune
it's called this because the surface is mainly sand, not soil
- As the marram grass and sedge grass dies, it adds hummus to the sand, creating soil. A grey dune develops, with plants such as gorse.
Salt marsh succession:
- Halophytic plants are specially adapted to saline conditions to colonise mud.
- The mixing of fresh water and seawater in the estuary causes clay particles to stick together and sink - called flocculation.
- Blue-green algae and gut weed colonise mud, exposed at low tide for only a few hours.
- The algae bind mud, add organic matter, and trap sediment.
- As the sediment thickens, water depth is reduced, and the mud is covered by tide for less time.
54
What are the 5 types of sand dunes?
- Embryo dunes
- Yellow dunes
- Grey dunes
- Dune slacks
- Climax
55
What are embryo dunes?
Pioneer species colonise the bear sand, e.g. prickly saltwort has a high salt tolerance and leaves that retain moisture. The root of these plants binds the Sand together.
56
What are yellow dunes?
The pioneer species die and decompose, helping to form a thin swim. Other species move in e.g. Marram grass. The soil is still alkaline but will begin to tolerate a wide range of plants.
57
What are grey dunes?
The soil deepens and becomes less alkaline as more organic matter forms. This is called Hummus. Small plants e.g. hawkweed and larger plants e.g. Heather move in.
58
What are dune slacks?
Dune slacks are very large depressions that are often deep enough to expose the water table. As freshwater is exposed at the surface, new types of vegetation such as reeds grow.
59
What is the climax?
The soil can eventually support large trees. Fast-growing trees e.g pine followed by slower-growing e.g Ash and oak. These gradually become the dominant climax species.
