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Geography > Coastal Processes and Landforms > Flashcards

Coastal Processes and Landforms Flashcards

1
Q

Constructive Wave

A

A wave that leads to the build up of a beach, due to the swash of the wave being more effective in moving material than the backwash.

  • Low frequency
  • Wave height under 1 metre
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2
Q

Destructive Wave

A
  • Created in storm conditions.
  • Created from big, strong waves when the wind is powerful and has been blowing for a long time.
  • Occur when wave energy is high, and the wave has travelled over a long fetch.
  • Tend to erode the coast.
  • Usually occur in winter
  • High frequency
  • Wave height over 1 metre
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3
Q

What are the main coastal processes?

A

Transportation, Mass Movement, Erosion and Weathering.

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4
Q

Transportation

A

The movement of material in the sea and along the coast by waves

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5
Q

Weathering

A

The breaking down or dissolving of rocks and minerals in-situ (where it is found)

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6
Q

Erosion

A

The geological process in which earthen materials are worn away and transported by natural forces such as wind or water.

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7
Q

Mass Movement

A

The movement of material downslope under the force of gravity.

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8
Q

Physical (freeze-thaw) Weathering

A

Rocks break due to a change in temperature.

Eg. water moves into cracks then freezes and expands causing hte cracks to widen.

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9
Q

Biological Weathering

A

Plants and animals break up rocks.

Eg. plant roots grow into rock cracks eventually forcing the rock to break in half.

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10
Q

Chemical

A

Acid in rainwater dissolves the rock.

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11
Q

Hydraulic Action

A

Erosion due to sheer power of waves crashing into cliffsides.

Air gets compressed / trapped in cracks by waves and the pressure causes cracks.

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12
Q

Abrasion

A

Pebbles / other sediment carried in waves is grinded against the base of a cliff causing it to be worn away. (similar to sandpaper)

Causes the cliff to become very smooth.

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13
Q

Attrition

A

When rocks carried in waves are knocked together causing them to be eroded (usually become rounded and smooth like rocks deposited on beaches.)

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14
Q

Solution (erosion)

A

When seawater dissolves certain types of rocks. Eg. Limestone and chalk (soft rocks) usually are prone to solution erosion.

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15
Q

Traction

A

Pebbles / larger sediments are rolled along seabed.

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16
Q

Saltation

A

Load is bounced along the sea bed, e.g. small pieces of shingle or large sand grains. (small sediment (lighter) )

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17
Q

Suspension

A

Small particles are carried in water, e.g. silts and clays, which can make the water look cloudy.

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18
Q

Solution (transportation)

A

Minerals are dissolved in seawater and carried in solution. The load is not visible.

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19
Q

Types of Weathering

A

Physical, Biological, Chemical

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20
Q

Types of Transportation

A

Solution, Saltation, Suspension, Traction

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21
Q

Types of Erosion

A

Hydraulic Action, Attrition, Abrasion, Solution

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22
Q

Types of Mass Movement

A

Soil creep, Slumping, Cliff Collapse

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23
Q

Soil Creep

A

Slow down-slope movement of earth materials under the influence of gravitation.

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24
Q

Slumping

A

Area of saturated land (ground filled with water) slips downhill.

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25
Q

Sea Wall

A

A wall / embankment put in place to prevent the sea eroding to the coast.

Advantages - Protects the base of cliffs. Prevents flooding. Protects nearby land and buildings.

Disadvantages - Expensive to build and maintain. Curved wall reflect wave energy –> waves remain powerful therefore the wall will eventually erode.

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26
Q

Groynes

A

A wooden barrier built at right angles to the beach.

Advantages - Prevents movement of beach material along the beach. Prevents longshore drift. Allows the build-up of beach –> creates a beacha ttraction for tourists

Disadvantages - Can be seen as unattractive. Costly to build + maintain. Increases erosion further up the coast.

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27
Q

Rock Armour / Boulder barriers

A

Large boulders piled up on the beach to absorb the energy of waves and encourage the build up of beach material.

Advantagements - Absorbs energy of the waves. Allows the build-up of a beach.

Disadvantagements - Can be expensive to obtain and transport the boulders.

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28
Q

What are the different coastal landforms?

A
  • Cliffs (+ wave cut platforms)
  • Headlands and bays
  • Caves, Arches, Stacks and Stumps
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29
Q

Slumping

A

Also known as rotational slip. It is a process of mass movement. It is triggered by saturation.

30
Q

Saturation

A

When the soil is unable to absorb more water.

31
Q

Wave cut notch

A

A dent at the base of a cliff (or another coastal landform) formed by erosion.

32
Q

Wave cut platform

A

A narrow flat area found at the base of a cliff made of a hard rock in comparison to the adjacent cliff. Smoothed by the eroded material dragged in the backwash.

33
Q

How are cliffs formed

A
  1. Waves attack the base of the cliff and erode it through processes like hydraulic action and abrasion.
  2. A wave cut notch is created at the base of the cliff.
  3. The cliff becomes unsupported (by base) and collapses.
  4. Material at the base of the cliff is smoothed out through abrasion forming a wave cut platform.
34
Q

How are headlands and bays formed?

A
  1. Headlands and bays form on discordant coastlines where there are layers of hard and soft rock next to the coast.
  2. Waves erode the different types of rock at different types of rates - soft rock erodes mroe quickly.
  3. Soft rock is eroded by processes like hydraulic action. It cuts backwards forming a concave shaped bay.
  4. The hard rock is eroded more slowly and the headland is left protruding out to sea.
35
Q

Discordant coastlines

A

Coastlines where the geology alternates between strata (bands) of hard rock and soft rock.

36
Q

How are caves, arches, stacks and stumps formed?

A

These landforms were headlands that have been eroded.

Headland –> caves –> arches –> stacks –> stumps

  1. Abrasion and Hydraulic action forms a cave.
  2. Erosion and waves cut through headland (cave) to form an arch which is continually widened at its base.
  3. The roof of the arch becomes too heavy to be supported and collapses.
  4. Wave cut notches undercut the stack. It collapses leavinga stump. The stump gradually disappears after time.
37
Q

Longshore Drift

A
  • Waves approach at an angle because of prevailing wind.
  • The swash deposits material at said angle.
  • Backwash carries material back at a 90 degree angle.
  • Zig Zag motion is continuous and slowly transports material up the beach.
38
Q

Gabions

A

Basket / container filled with rocks / stones and earth.

Pros

  • Easy to transport, good drainage and the cheapest form of hard engineering.

Cons

  • Can be broken and lost / moved in storms + unattractive.
  • Birds may be hurt by the wire on the gabions
39
Q

Dune stabilisation

A

Planting vegetation on dunes in order to stabalise them. (soft engineering)

Pros

  • Only checked twice a year, cheap, provides habitats for animals + maintains natural look.

Cons

  • Have to be protected from pedestrians, can be damaged by waves, some areas may not be able to support dunes.
40
Q

Beach replenishment/reprofiling

A

Replenishment - Artificial sand placed on beach (dredged from seafloor)

Reprofiling - Beach sand moves up beach

(Soft engineering)

Pros

  • Preserves beach, widens beach, safe for visitors.

Cons

  • Temporary (will erode again - longshore drift will move it) + very expensive
  • Construction can kill wildlife.
41
Q

Beaches

A

Deposits of sand that lie between the high and low tide levels. Mainly found in bays because the waes that enter the bay are constructive waves that have a strong swash and weak backwash, –> thus build up the beach.

Most beaches are formed of sand and shingle as well as mud and silt.

42
Q

Beach formation

A

Beaches are made up from eroded material that has been transported and then deposited by the sea.

Deposition occurs when waves have limited energy, so beaches often form in sheltered areas like bays.

Constructive waves build up beaches as they have a strong swash and a weak backwash.

Sandy beaches are usually found in bays where the water is shallow, and the waves have less energy.

Pebble beaches often form where cliffs are being eroded, and where there are higher energy waves.

Beaches profile has lots of ridges called berms. They show the lines of high tides and storm tides.

A sandy beach typically has a gentle sloping profile, whereas a shingle beach can be much steeper.

The size of the material is larger at the top of the beach, due to the high-energy storm waves carrying large sediment.

The smallest material is found nearest the water as the waves break here and break down the rock through attrition.

43
Q

Spit

A

A spit is an extended stretch of sand or shingle jutting out into the sea from the land. Spits occur when there is a change in the shape of the landscape or there is a river mouth.

  1. Sediment carried along the coastline by longshore drift.
  2. Coastline change direction but longshore drift continues in the same direction.
  3. Material is deposited in the sheltered water beyond the headlnd. It builds upwards and outwards forming a spit.
  4. Winds blow in another direction forming a hooked end on the spit.
  5. Salt march develops in sheltered area behind the spits.
44
Q

Sand Dunes

A

Large heaps of sand that form on the dry backshore of a sandy beach.

For a sand dune to form it needs…

  • An obstacle (eg. driftwood) for dune to form against
  • Large flat beach, lare supply of sand, onshore wind to move sand to the back of the beach
  • Large tidal range (time for the sand to dry)

Berm – Embryo – Fore – Yeallow – Grey –Slack – Mature

Least – Most vegetation

45
Q

Dune types

A

Embryo - Mainly sand + some marram grass (dune forms around wood/rock/shingle)

Fore - Sand + plants (embryo dunes are stabilised by vegetation)

Yellow - Yellow sand + marram grass

Grey - Grey sand + more fiverse (soil nutrients high bc of rotting vegetation)

Slack - pond

46
Q

Slumping

A

Area of sturated land slips downhill.

  1. Soft boulder clay holds rainwater and runoff.
  2. Waves erode the base of the cliff. Wave cut notch is formed - Clay becomes saturated, forms a slip plane.
  3. Weight of saturated cliff causes it to slump. Cliff collapse occurs.
47
Q

Headlands + Bays

A

Formed at coastlines with alternating layers of rock (hard, soft) - called discordant coastlines.

Soft rock = Bay , bc it erodes faster.
Hard rock = Headland, bc it erodes slower.

48
Q

Cliffs (+ How they are created)

A
  • Most common feature on a coast, steep faces of rock and soil.
  • Shaped by erosion / weathering
  • On soft rock cliffs (eg. clay) cliff slumping occurs –> thus concave shaped shape.
  • On hard rock cliffs, cliff collapse is more common –> thus vertical face.
  1. Waves erode the base of the cliff through processes such as hydraulic action.
  2. Wave cut notch is created at the bottom of the cliff.
  3. Cliff becomes unsupported and collapses.
  4. Material at the base of the cliff is smoothed through material being pulled back (abrasion).
49
Q

Wave cut platform

A

Narrow, flat area found at the base of a cliff caused byt hardrock + eroded material dragged in backwash.

50
Q

Holderness (Causes of Erosion)

A

Made of boulder clay → soft (easily eroded)

Erosion = wave cut notch → saturated sediment + slip plane = slumping

Strong currents transport material along shore → less beaches → cliffs are exposed = faster erosion.

Northern part = chalk = headland = Flamborough head.

51
Q

Holderness (Effects of cliff recession)

A
  • 14 villages have been lost since Roman times.
  • Farmers have lost property → force to migrate / diversify.
    Eg. Ringborough farm lost ½ of property since 1939 → had to migrate backwards from coast + diversify → also sells bottled gas.
  • Hard engineering necessary by Hornsea + other places.
  • Means that it speeds up erosion further down the coast.
  • Bad for other settlements + Spurn Point.
  • Spurn Point is home to several bird species, mostly waders –> at risk of eroding –> loss of habitat.
52
Q

Holderness (Coastal management - Defenses)

A
  • Use of groynes to trap moving beach material and provide a protective beach in front of the cliff
  • The construction of sea walls and revetments as wave-resistant structures at the base of the cliffs
  • Artificial off-shore breakwaters like tyres and concrete blocks, forcing waves to break off-shore.
  • Sea wall used to protect Easington Gas Station (cost 4.5 million)
53
Q

Holderness (Defences at Mappleton)

A
  • 1991 rock revetment + 2 rock groynes built to encourage beach buildup. –> decreases erosion bc waves break on beach.
  • However caused erosion to speed up south of Mappleton.
54
Q

Managed Retreat

A
  • Small villages + farmland don’t get protection (at least not hard engineering)
  • Eg. Kilnsea has not been defended.
  • Managed retreat is when settlements / people are slowly moved backwards away from the coast.
  • Eg. Caravan park for every 4 caravan bases lost to the sea, the council pays for 5 more bases. –> managed retreat.
55
Q

Tropical Storm (Formation)

A
  • Made when thunderstorms move across tropical ocean (27C )
  • Warms air above ocean → warm air rises → forms clouds + low pressure area
  • Air moves into low pressure area → increase in wind speed etc etc
  • Trade winds blow wind + spinning of earth causes the tropical storm to spin.
  • May take hours / days to fully form
56
Q

Hurricane Katrina Case Study (Impacts)

A
  • August 2005
  • Category 4 storm + storm surges above 6 metres.
  • New orleans worst affected → Levees broke → flooding → evacuation order but poor stayed
  • 1.2 million homeless + 1200 people died
    People sought refuge in superdome stadium → unhygienic
  • Oil facilities damaged → petrol prices rose in UK + USA
57
Q

Hurricane Katrina (Responses)

A
  • UK sent food aid.
  • National guard mobilised (maintain + restore law and order)
  • $50 billion dollars by the government in aid.
58
Q

U.S. Gulf Coast (Threats)

A

Annually approx. 10 tropical storms develop over the ocean in this area → about 6 become hurricanes. Eg. Hurricane Katrina

BP oil spill 2010 → economic consequences for fishing, tourism + oil industry. + consequences for human health. (Largest marine oil spill)

Rising sea levels = flooding risk.

59
Q

U.S. Gulf Coast (Oppurtunities)

A

Beaches in Florida = tourism = jobs + economic growth

Commercial fishing = multi-million dollar industry in gulf of Mexico.

Oil industry → home to ⅕ of crude oil production in US + 45% of US petroleum refinement.

Port of Louisiana + Houston = very important for the economy.

60
Q

What are Coral Reefs

A

Coral reefs = large underwater structures made of the skeletons of coral, = marine invertebrate animals.
Individual coral = polyp → excrete calcium carbonate → produces hard exoskeleton to protect the soft body. Polyps grown on the exoskeleton
New polyps grow on existing exoskeletons → coral → coral reefs.
Several polyps form a colony (coral) → several colonies form a reef.
Algae live in the tissue of polyps → symbiotic relationship (coral house algae + algae makes food for both)
Polyp = translucent → take on colour of algae.
Coral under stress → evict algae = coral bleaching

61
Q

Where are coral reefs located?

A
  • Coral reefs located in tropical oceans near the equator.
  • Found 30 degrees north and south of the equator.
  • Largest coral reef is the Great Barrier Reef in Australia.
  • Second largest coral reef can be found off the coast of Belize, in Central America.
  • Other reefs found in Hawaii, the Red Sea, + other areas in tropical oceans.
62
Q

What conditions do coral reefs need to develop?

A
  • Usually found 30 degrees north south of equator –> ocean temperatures perfect. Cant survive below 18 degrees celsius.
  • Optimum temp 22-25 C
  • Need shallow water (max 60m) + clear water –> light can reach reefs –> algae can photosynthesise –> coral feed on algae
  • If sediment settles on polyps, they are unable to feed.
  • Cant grow above tide level bc they need oxygen + water brought by breaking waves + can’t survive lone periods above water.
  • Grow best in conditions of high salinity as freshwater kills coral. For this reason, breaks in reefs often occur at river mouths.
63
Q

Fringing reefs

A

Fringing reefs, the most common type, extend outward from a body of land with no water separating the reef from land.

64
Q

Barrier reefs

A
  • Barrier–> Barrier reefs are platforms separated from the shoreline by a channel or a lagoon.
  • Barrier reefs are created due to the sea level rising or the land sinking. The coral grows upwards so they can continue to photosynthesize, and this leaves a gap between the land and the reef.
  • The longest barrier reefs are found along the coasts of Belize and Australia.
65
Q

Atoll Reef

A
  • Atolls are coral islands that consist of a narrow, horseshoe shaped reef with a shallow, central lagoon.
  • They often form around volcanic islands that have sunk due to the process of subduction.
  • Over 300 atolls are found throughout the South Pacific.
66
Q

The Great Barrier Reef

A
  • A barrier reef
  • Sits on remains of the Great Dividing Range (mountain system NorthEast of Australia)
  • Polyp’s attached to remains of mountain range
  • Largest and longest reef complex in the world –> 1,250 miles.
  • Largest structure made of living organisms.
  • Very little variation in sea temperature –> optimum temperature achieved –> perfect for coral growth.
  • Water also crystal-clear up to 100 feet
  • Very biodiverse –> contains 400 types of coral, 1500 types of fish + 4000 types of mollusk. + has sea cow + green turtle (nearly extinct)
67
Q

What are mangroves?

A
  • Mangroves are trees or shrubs which grow in tidal, tropical, coastal swamps.
  • They have tangled roots that grow above ground and form dense thickets.
  • It is thought that they originate from South-east Asia and then spread across the globe.
  • Because they grow in the intertidal zone, they live in a constantly changing environment.
68
Q

Where are mangroves located

A
  • In sheltered tropical and subtropical coastal areas.
  • In general, this is an area between latitudes of 30 degrees north and 30 degrees south of the equator.
69
Q

Conditions needed for development (Mangroves)

A
  • Thrive in hot, muddy, salty conditions (would quickly kill most plants)
  • Most grow in warm waters (30 degrees north + south of the equator)
  • Only grow in areas where the temperature remains above 20 degrees Celsius
  • Grow in calm, shallow, sheltered areas with no strong waves or currents.
  • Develop in areas where there is a large area between the high and low water mark.
70
Q

Characteristics (Mangroves)

A
  • Mangrove swamps contain many different species of tree.
  • Live in salty water as they are halophytes (salt tolerant plants).
  • Home to a diverse range of species including fish, birds, frogs, snakes, crocodiles, swamp rats, monkeys and tigers.
  • Create a barrier to the shoreline and protect it from storms.
71
Q

The Sundarbans, Bangladesh (Mangroves)

A
  • Sundarban = large 10,000 km² mangrove forest in Bay of Bengal (formed by super confluence of Ganges + other rivers)
  • Freshwater swamp first lie inland from mangrove forests
  • Intersected by a network of waterways + small islands = accessible by boat.
  • Fertile soils → converted to agriculture.
  • Home to spotted deer, Bengal tiger + crocodiles.
  • Protective barrier for millions against flooding.
  • UNESCO world heritage site

Geography (14 decks)

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