Coasts Flashcards

Question

What is the process of erosion and what types are there?

Answer 1

Erosion is a collaborative process which involves the removal of sediment from a coastline by different types of erosion, not one type acting by itself. The main types are: - Corrasion - Abrasion - Attrition - Hydraulic action

Answer 2

Sand and pebbles are picked up by the sea from an offshore sediment sink or temporal store and hurled against the cliffs at high tide, causing the cliffs to be eroded. The shape, size, weight and quantity of sediment picked up, as well as the wave speed, affects the erosive power of this process.

Answer 3

This is the process where sediment is moved along the shoreline , causing it to be worn down over time. It is like a sandpaper effect, causing the rock to often look smooth and polished

Answer 4

Wave action cause rocks and pebbles to hit against each other , wearing each other down and so becoming round and eventually smaller. Attrition is an erosive process within the coastal environment, but has little to no effect on erosion of the coastline itself.

Answer 5

As a wave crashes onto a rock or cliff face, air is forced into cracks, joints and faults within the rock. The high pressure causes the cracks to force apart and widen when the wave retreats and the air expands

Answer 6

The mildly acidic seawater can cause alkaline rock such as limestone to be eroded and is very similar to the process of carbonation weathering

Answer 7

- **Waves** - **Subaerial processes (weathering and mass movement)** e.g. landslides weaken cliffs. Rock fragments as a result of these processes may lead to increased corrasion and abrasion - **Rock type** - **Faults in the rock** - **Beaches** beaches will decrease effects of erosion

Answer 8

Coastal transportation is responsible for transferring sediment within a sediment cell and between other sediment cells. The four main processes of transportation are: ● Traction ● Saltation ● Suspension ● Solution

Answer 9

Large, heavy sediment rolls along the sea bed pushed by currents (like a tractor wheel)

Answer 10

Smaller sediment bounces along the sea bed, being pushed by currents . The sediment is too heavy to be picked up by the flow of the water

Answer 11

Small sediment is carried within the flow of the water. The Hjulström curve shows how greater velocities of water are able to suspend larger and heavier pieces of sediment

Answer 12

Dissolved material is carried within the water, potentially in a chemical form. This method of transportation is an important part of carbonation weathering

Answer 13

1. Waves hit the beach at an angle determined by the direction of the prevailing wind 2. The waves push sediment in this direction and up the beach in the swash 3. Due to gravity, the wave then carries sediment back down the beach in the backwash 4. This moves sediment along the beach over time

Answer 14

Deposition occurs when sediment becomes too heavy for the water to carry, or if the wave loses energy. Deposition tends to be a gradual and continuous process, so a wave won’t release all its sediment at the same time

Answer 15

This is an important process in salt and tidal marshes. Clay particles clump together and then sink due to their high density

Answer 16

Weathering is the breaking down of rocks in situ (where they are). It is caused by day-to-day changes in the atmosphere such as temperature and precipitation. The types of weathering are: - Mechanical - Biological - Chemical - Onion-skin

Answer 17

The breakdown of rocks due to exertion of physical forces without any chemical changes taking place ● **Freeze-thaw**: Water enters cracks in rocks and then the water freezes overnight during the winter. As it freezes, water expands by around 10% in volume which increases the pressure acting on a rock, causing cracks to develop. Over time these cracks grow, weakening the cliff making is more vulnerable to other processes of erosion ● **Salt Crystallisation**: As seawater enters cracks then evaporates, salt is left behind. Salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen. Salt can also corrode ferrous (materials that contains iron) rock due to chemical reactions ● **Wetting and Drying**: Rocks such as clay expand when wet and then contract again when they are drying. The frequent cycles of wetting and drying at the coast can cause these rocks and cliffs to break up ● **Onion-skin**: * During the day the sun heats up the surface of the rock, causing the rock to expand. During the night the rock cools down and contracts. As the rock expands and contracts over and over again small pieces of surface rock begin to fall and flake off

Answer 18

Frost-shattered pieces of rock

Answer 19

The breakdown of rocks by organic activity - Piddocks (shellfish that bore into rocks) - Seaweed and algae secretes chemicals capable of promoting solution - Plant roots can get into tiny cracks and open them up further - Decaying plant roots produce acid which chemically eats away at rocks - Burrowing animals such as Puffins

Answer 20

The breakdown of rocks through chemical reactions - **Acid rain**: nitrogen and sulphur oxide produce much more acidic rain that can rapidly chemically dissolve rocks - **Carbonation**: carbon dioxide gas dissolves into rain to form weak carbonic acid. This very slowly eats away at certain rocks like chalk and limestone - **Oxidation**: when rocks are broken down by oxygen in the air. It makes them go a rusty colour. Rocks which contain iron are prone to this

Answer 21

Mass movement is the movement of material down a slope under the influence of gravity. The four categories are: - **Creeps** - **Flows** - **Slides** - **Falls** - **Slumps** e.g. rockfall, landslide, landslip

Answer 22

● Initially, faults in the headland are eroded by hydraulic action and abrasion to create small caves ● Marine erosion widens faults in the base of the headland , widening over time to create a cave ● The cave will widen due to marine erosion and sub-aerial processes, eroding through to the other side of the headland, creating an arch ● The arch continues to widen until it is unable to support itself, falling under its own weight through mass movement, leaving a stack as one side of the arch becomes detached from the mainland ● With marine erosion attacking the base of the stack, eventually the stack will collapse into a stump ● A wave-cut platform will be left afterwards

Answer 23

A blowhole is formed as sea caves grow landwards and upwards into vertical shafts and expose themselves towards the surface, which can result in blasts of water from the top of the blowhole is the gemoetry of the cave and state of the weather are appropriate

Answer 24

A bay is a crescent-shaped indentation in the coastline found between two headlands. It usually has a beach which is composed of sand or shingle (soft rock) For example, Swanage

Answer 25

A headland is a cliff that sticks out into the sea, so it is surrounded by water on three sides. Headlands are composed of hard rock such as granite, chalk or limestone, which are resistant to erosion For example, Durlstone Head

Answer 26

Bays and headlands are formed on discordant coastlines when there is a section of soft rock between hard rock on a coast line. The soft rock and hard rock have differential erosion with the soft rock eroding faster to the waves therefore the hard rock cliff stick out, creating headlands

Answer 27

A coastline where the geology is parallel

Answer 28

A coastline where the geology is perpendicular. Features such as headlands and bays will be sene here

Answer 29

**Swash-aligned**: Waves break perpendicular to coast so there is limited longshore drift. Sediment doesn’t travel far along the beach. Wave refraction may reduce the speed of high energy waves, leading to the formation of a shingle beach with larger sediment Swash aligned beaches are more influenced by constructive wave patterns, which are also important for building up large beaches. In contrast, drift aligned coasts bring in waves at an angle to the shoreline and so therefore, the waves tend to transport sediment down the coast, keeping beaches relatively narrow. **Drift-aligned**: Waves approach at an angle, so longshore drift causes the sediment to travel far along the beach, which may lead to the formation of a spit at the end of a beach. Generally larger sediment is found at the start of the beach and weathered sediment moves further down the beach through longshore drift, becoming smaller as it does, so the end of the beach is likely to contain smaller sediment

Answer 30

This is a long narrow strip of land which is formed when longshore drift causes the beach to extend out to sea, usually due to a change in direction of the coastline. This sediment projection can create a salt marsh due to the sheltered, saline environment where water flow speed is lower, allowing deposition of finer sediments to occur. The length of the spit depends on any changing currents or rivers, which will prevent sediment from being deposited . This means a spit can never extend across an estuary. A change in wind direction or wave direction can cause the end of the spit to curve

Answer 31

A barrier beach occurs when a beach or spit extends across a bay to join two headlands . This traps water behind it leading to the formation of a brackish lagoon which is separated from the sea. As well as forming from present day processes, some barrier beaches may have formed due to rising sea levels after the last glacial period , when meltwater from glaciers deposited sediment in the coastal zone. If a barrier beach becomes separated from the mainland, it becomes a barrier island. T hey are common in areas with low tidal ranges

Answer 32

A tombolo is a bar or beach that connects the mainland to an offshore island and is formed due to wave refraction off the coastal island reducing wave velocity , leading to deposition of sediments. They may be covered at high tide if they are low lying.

Answer 33

An offshore region where sand is deposited , as the waves don’t have enough energy to carry the sediment to shore. They can be formed when the wave breaks early, instantly depositing its sediment as a loose-sediment offshore bar. They may also be formed as a result of backwash from destructive waves removing sediment from a beach. Offshore bars may absorb wave energy, reducing erosion in some areas.

Answer 34

1. Sand accumulates against a feature and builds upper beach height 2. Wind speed drops behind accumulation resulting in more sand deposition 3. Marram grass colonises embryo dunes stabilising further dune migration 4. Marram leaves further reduce wind speed and capture more blown sand. Decaying plants add humus 5. Microclimate and soil conditions change allowing colonisation by additional species

Answer 35

- **Embryo dunes**: Upper beach area where sand starts to accumulate around a small obstacle (driftwood, wooden peg, ridge of shingle) - **Yellow dunes**: – As more sand accumulates and the dune growns, vegetation may develop on the upper and back dune surfaces, which stabilises the dune. - **Grey dunes**: – Sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth and giving it a greyer colour - **Dune slacks**: The water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of moisture-loving plants (e.g. willow grass) - **Heath and woodland**: Sandy soils develop as there is a greater nutrients content, allowing for less brackish plants to thrive. Trees will also grow (willow, birch, oak trees) with the coastal woodland becoming a natural windbreak to the mainland behind

Answer 36

Salt marshes tend to develop in sheltered areas such as behind a spit where there are no strong tides or currents to prevent sediment deposition and accumulation. As most of the sediment is small, this leads to a build up of mud via flocculation, which over time builds up until it is above the water level. Pioneer plants colonise this area, leading to more sediment becoming trapped. A meadow is formed as sections of the salt marsh rise above the high tide level, leading to the climatic climax of the vegetation succession

Answer 37

- Thermal expansion (as ocean water warms, it expands) - Increased melting of land-based ice - Human-induced global warming (1.7mm per year sea level rise)

Answer 38

Isostatic change occurs when the land rises or falls relative to the sea and is a localised change caused by a growing or declining ice sheet. Isostatic sea level change is often a result of isostatic subsidence (glaciers weigh down the land beneath, and so the land subsides). When the glaciers melted, this has lead to isostatic recovery and the coastline to rebound and rise again in the areas that were covered by ice. In the UK, Scotland and the north-west of England are rising at around 1.5mm per year as they were previously covered by glaciers, but the land in the south-east subsides at around 1mm a year as the ice was thinner and so there was less pressure on the crust

Answer 39

A rise or fall in sea level because of the amount of sea water across the whole planet is called Eustatic change. Eustatic change may be due to thermal expansion/contraction or changes in glacial processes. Thermal expansion is the process of water expanding when it gets warmer, and so the volume of water increases leading to rising sea levels. In the last ice age, sea levels were over 100m lower than they are currently due as the water was stored in large ice caps as the majority of precipitation fell as snow. When the ice caps melted, this lead to rising sea levels. As a result of global warming, both processes are acting to increase sea levels

Answer 40

Where the land has been raised in relation to the coastline, landforms such as arches, stacks and stumps may be preserved

Answer 41

Landforms of submergence occur when the sea level rises or the coastline sinks in relation to the sea. Rising sea levels leads to the following landforms: - Rias - Fjords - Dalmation Coastlines

Answer 42

Composed of long, narrow islands running parallel to the caostline separated by narrow sea channels. They are produced by sea-level rise flooding the shoreline where geology creates valleys aligned parallel to the caost. The best example of a dalmation coast is the Dalmation Coast in Croatia

Answer 43

A ria is a drowned (flooded) river valley (V-shaped). Rias are formed when rising sea levels flood narrow winding inlets and river valleys . They are deeper at the mouth of the inlet, with the water depth decreasing further inland.

Answer 44

Fjords are drowned glacial valleys rather than drowned river valleys. Deep water + predominently salt water. They are dangerous due to mass movement causing tsunamis (large rocks breaking off and falling into water) Fjords are formed when rising sea levels flood deep glacial valleys to create natural inlets and harbours

Answer 45

**Cost-benefit analysis.** This is carried out before a coastal-management project is given the go ahead. Coasts are forecast e.g. a sea-wall along with its design, maintenance, cost and then compared with the expected benefits e.g. the value of land saved, housing protected, savings. Costs and benefits are either: - **Tangible** - where costs and benefits are known and can be given monetary value - **Intangible** - where costs may be difficult to assess but are important

Answer 46

- **Hard engineering** - man made structures that aim to prevent erosion . They are often very effective at preventing erosion in the desired area, but are high cost and have a significant environmental impact due to the use of concrete and other man-made materials. - **Soft engineering** - aims to work with and complement the physical environment by using natural methods of coastal defence. They are useful for protecting against sea-level change as well as coastal erosion.

Answer 47

- Beach nourishment - Cliff regrading (make cliff less steep) - Dune stabilisation - Marsh creation

Answer 48

- Groynes - Sea walls - Concrete tetrapod (tetrahedral shape to dissipate the force of incoming waves by allowing water to flow around rather than against them) - Revetments (wooden/concrete ramps) - Offshore breakwater (rock barrier forcing waves to break) - Rock armour/riprap

Answer 49

Stretch of coast begins at Flamborough Head and ends at Spurn. _Flamborough Head_ Cliffs made of chalk -> resistant rock, distinctive white colour The sea is actively undercutting and eroding the base of the cliffs leading to fequent rockfalls. Wave refraction concentrates wave energy on the headland and lack of beach renders cliffs more vulnerable. One of the most recognisable features on the map in the UK (tourist attraction). Natural environment is economically beneficial. SMP: Do Nothing. This is because of the slow erosion rate withing this area meaning no settlements or properties are at threat _Hornsea & Mappleton_ Land made of boulder clay deposited by glaciers -> retreats at 10x the rate of chalk cliffs Management is aimed at protecting hotels, arcades and creating a sandy beach as they are economically valuable and there is settlement. Spent money on wooden groynes, gabions and a concrete sea wall alongside riprap, groynes and beach nourishment at Mappleton to produce a sandy beach. Hornsea cliffs are a popular tourist destination but have a rapid rate of cliff retreat SMP: Hold the line _Easington_ 2.25% of all UK gas comes through gas terminal at Easington. £4.45 million spent on riprap to protect the terminal/village. The terminal is one of the six main gas terminals in the UK Locals disagreed about where sea defences are located as they mainly protect the terminal and not the village SMP: Hold the line _Spurn_ Spit made of sand and shingle. 6km long. Salt marsh developed behind it due to the saline conditions. Groynes in the north on Hornsea disrupt LSD, spit recieves less sediment opening it up to erosion. Protected with groynes and rock armour but is at risk of losing habitats due to the lack of sediment to maintain the spit. Extremely narrow for much of its length and has been frequently breached and destroyed by major storms. Plays an important role in protecting the town and land bordering River Humber from effects of flooding and storm waves SMP: No active intervention/managed realignment

Answer 50

The Sundarbans is a coastal zone occupying the world's largest delta, that extends over 10,000km2 of southern Bangladesh and India on the Bay of Benga. The delta is formed from the sediment deposited by the Ganges, Brahmaputra and Meghna rivers. The natural climax ecosystems of the Sundarbans are mangrove forests and swamps where Bengal tigers use as their habitat. **Challenges** - Tiger attacks - Coastal flooding - Salinisation of soil - Remoteness/ lack of accessibility due to few roads - Cyclones - Lack of knowledge of coastal issues by those in charge - Deforestation of mangroves due to population growth inceasing flood risk and conflict with bengal tigers - Located on big flood plain - Destructive shrimp farming - Poor communications - High poverty - General lack of employment **Resilience** - Solar energy project set up so people spend less time in forests meaning less exposure to tigers - The light deters the tigers and means shops can stay open at night - Trackers on tigers - Better roads and bridges being built - Public Health Engineering department is improving access to clean water and sanitation **Mitigation** - Investment in physical infrastructure - Government plan to move 1.8mil people to cyclone shelters - Planting of 16 million mangroves to strengthen existing manmade structure as mangroves decease windspeed by 20km - Mangrove restoration stores 700,000 tonnes of CO2 **Adaptation** - Salt-resistant rice planted by countless farmers to help feed the Sundarbans population as rice usually requires an abundance of water, this is disrupted when storm surges cause salt-water flooding - US-Aid provides better info on climate change and biodiversity. Promotes green energy and solar panels and has helped 100,000 people from 15,000 hectares of land with better tools

Answer 51

**Integrated Coastal Zone Management** Brings together those involved in department, management and use of the coast because human actions in one place affect other places down coast. Management occurs between different political boundaries , which is both beneficial and problematic as decision making is likely to be a longer process. Aim is to establish sustainable levels of economic and social activity, resolve environmental, social, economic challeneges and protect coastal environment. ICZMs provide a more holostic overview of the coast

Answer 52

**Shoreline Management Plans** For each sediment cell in the UK, an SMP has been created to help with coastline management. Each SMP identifies all of the activities, both natural and human which occur within the coastline area of each sediment cell. Four options are considered for each stretch of the coastline: ● **Hold the Line**: Defences are used to maintain the current position of the shoreline ● **Managed Retreat**: Defences and engineering techniques are used to allow the coastline to advance inland and create its own natural defences such as salt marshes ● **Advance the Line** : Defence are built to try and move the shoreline seawards, potentially to protect an important population centre or tourist amenity ● **No Active Intervention**: The coastline is exposed to natural processes

Answer 53

[4 marks] Saltmarsh environments develop in sheltered estuaries behind spits. Silt is deposited by the river which gradually builds up to form an intertidal mud flat. The mud flat continues to build and rise above sea level with the addition of further silt. Vegetation which is highly adapted to environment colonises the mud which itself traps further sediment.

Coasts Flashcards

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