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Geography > Coasts EQ2 > Flashcards

Coasts EQ2 Flashcards

1
Q

Describe the form of Blockfalls

A

They may involve the detachment of single fragments or of a whole section of cliff that breaks up as it descends

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2
Q

What does wave size depend on?

A
  • the strength of the wind
  • the duration the wind blows for
  • water depth
  • wave fetch
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3
Q

What are berms?

A

A series of smaller ridges formed beneath a storm ridge.

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4
Q

How are tombolos formed?

A

LSD builds a spit from land until it meets an island

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4
Q

What are blowouts

A

Blowouts are sandy depressions in a sand dune ecosystem (psammosere) caused by the removal of sediments by wind.

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5
Q

How do flows occur

A

When unconsolidated fine grained sediment mix with large volumes of water. They become saturated, lose their cohesion and flow downslope

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6
Q

Explain how salt crystillisation works.

A

When waves break on coastal rocks, the water evaporates, leaving sodium and magnesioum salt compounds in joints and cracks. These salt compounds grow and expand and exert pressure and fore the rocks apart.

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6
Q

What is abrasion?

A

Abrasion is where sediment picked up by breaking waves is thrown against the cliff face. This sediment then acts in the cliff like a tool, chiselling away at the surface and gradually wearing it down.

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7
Q

How are cuspate forelands formed

A

When longshore drift currents from opposing directions converge at the boundary of two sediment cells.

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8
Q

What do transfers include

A

LSD, Waves, Tides, currents and wind

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8
Q

How do offshore bars form?

A

Forms in shallow water, where destructive wave break before reaching the beach

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8
Q

What is negative feedback?

A

Tends to maintain equilibrium, e.g. wave erosion causes rock falls which protects the base of a cliff from further erosion.

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9
Q

What is a barrier beach

A

Linear ridges of sand/shingle extending across a bay and are connected to land on both sides. Forms a lagoon behind

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10
Q

Describe the wave break of destructive waves.

A

When wave breaks material is thrown up on beach creating a steep shingle beach

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11
Q

How are waves formed?

A

Waves are caused by friction between wind and water transferring energy from the wind into the water
–> ripples –> waves

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11
Q

What develops behind a barrier beach.

A

Since it is a low energy environment, salt marshes and other natural ecosystems may develop.

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11
Q

Explain the effects of freeze-thaw

A

Angular rock fragments and a jagged clifface with a scree slope at the base.

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12
Q

What do cliffs prone to blockfall have?

A

Geological structure of many joints, faults or bedding planes
Steep, near vertical dip of strata.

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12
Q

What are cuspate forelands

A

Cuspate forelands are low lying triangular shaped headlands, extending our from a shoreline, formed from deposited sediment

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13
Q

What is corrosion?

A

Corrosion is where carbonate rocks (limestone) are vulnerable to solution by rainwater, spray from the sea and seawater.

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13
Q

What are the effects of oxidisation

A

The rock minerals will no longer be bonded together so erosion is easier.

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14
Q

What is an example of a barrier beach.

A

Chesil beach in dorset.

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15
Q

How are barrier beaches formed

A

LSD extends a spit across the bay
Rising sea level so that waves move the sand towards the shore.

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16
Q

What is rotational slumping?

A

Rotational slumping is where a section of a cliff remains intact as it moves down a cliff along a curved slip plane

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16
Q

What is percolation

A

Percolation is the process by which water moves downward through the soil under gravitational forces

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17
Q

What are double spits?

A

Where spits form on either side of a large bay, but do not join because river currents pass out into sea between the spits.

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18
Q

Define mass movement

A

Mass movement is the transport of rock down a slope as a result of gravity.

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19
Q

Why does rotational slumping occur / occur in?

A

Weak rocks
Unconsolidated materials
Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction

19
Q

How are storm ridges created

A

From destructive waves throwing pebbles or scouring sediments away.

20
Q

Where do blockfalls occur and Explain the process of blockfalls

A

Occurs on slopes >40 (steep slope), where rock fragments break away and drops vertically or bounces downslope. Its initiated by mechanical weathering and marine erosion

21
Q

What is an example of a cuspate foreland and briefly give details.

A

Dungeness in Kent
-11km in a south east direction
2 spits converging at distal ends

22
Q

What is a tombolo?

A

Tomobolos are linear ridges (or bar) of sand and shingle connecting an offshore island to the coastline of the mainland.

23
Q

Where happens in the source

A

Erosion, subaerial processes, river transport etc

24
Q

What are talus scree slopes?

A

Where angular rock fragments fall to the base of the cliff
They are steep, fan shaped mounds of angular material.
Larger boulders at their core

24
Q

Explain how sea weed acids work.

A

Some seasweed cells contain pockets of sulfuric acid so when these cells break in contact with rock, the acid will disolve some rock minerals

25
Q

What happens in the sinks

A

Deposition and depositional landforms are created.
spits, offshore bars, sand dunes.

26
Q

What are the effects of salt crystallisation

A

Angular rock fragments are loosened and fall to create scree-slopes at the base of the cliff, or rock faces crumble away.

26
Q

why has sea levels risen in the risen since the end of the ice age?

A

Thermal expansion due to climate change

26
Q

How can a sediment budget be calculated?

A

The amount of sediment gained from sources and lost to sinks can be calculated.

27
Q

What is fetch?

A

Fetch is the uninterrupted distance across water over which a wind blows - and therefore the distance waves have to grow in size.

28
Q

What are constructive waves?

A

Where the waves have a strong swash due to being elliptical, and a weak backwash as water percolates into the material instead of running off the surface.

29
Q

What is the most optimum angle for waves to approach the beach in LSD

A

30 degrees

30
Q

What is the sediment cell concept briefly

A

A sediment cell is a linked system of sources, transfers and sinks of sediment along a section of coastline.

30
Q

Explain how frost-shattering works

A

Only found where the temperature changes daily above or below 0. Water seeps into the rock and freezes and the rock expands –> exerts pressure and breaks the rock.

30
Q

What are beach cusps?

A

beach cusps are when waves are being refracted (bending) and have a bending swash from two opposite directions and has a single backswash

30
Q

What is the frequency of constructive waves?

A

6-8 per minute.

31
Q

What are runnels

A

Runnels are water-filled troughs on the beach.

32
Q

What are recurved spits?

A

As a spit grows longer, tides, river currents, and other wave directions turn the end of the spit into a hook

32
Q

Explain how oxidation works.

A

OXygen combines with iron-based minerals in the rock, causeing a chemical breakdown of the rock.

32
Q

Describe the process of weathering.

A

Break down of rocks in situ, by exploiting the weakness in the rock and produces loose sediments

33
Q

Explain the processes of caves, arches, stack and stumps.

A

Caves: Marine erosion attacks base of headlands widening it to form a cave
Arch: Subaerial processes and erosion erodes to the other side of the headland.
Stack:The arch continues to widen until it cannot support itself –> falls under gravity and own mass.
Stump:Marine erosion attacks the base of the stack –> collapses –> stump

34
Q

What is positive feedback?

A

tends to increase change in a system until a new equilibrium is reached e.g. a blow out in a sand dune allows more sand to be eroded by the wind, reducing vegetation cover.

34
Q

What do sources include?

A

Erosion of cliffs, land sediments transported by rivers, wind-blown sediment from the land, onshore currents bringing sediment to shore

35
Q

What are the characteristics of a destructive wave.

A

Have a stronger backwash and a weak swash - removes sediment.

36
Q

When are erosion rates highest in the year

A

Winter months

36
Q

How much pressure is exerted during hydraulic action?

A

50kg/cm3

37
Q

Explain how boring molluscs work

A

Marine molliscs scrape away rock to get food or bore away rock to make a home

38
Q

What is hydraulic action?

A

where large destructive waves break on a cliff and the water exerts pressure on the cliff

39
Q

What is attrition

A

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.

40
Q

Explain how a wave cut platform is formed

A

Cliff erodes at base –> collapses due to gravity –> cliff retreats –> sloping rock in between low and high tide

40
Q

What is the wave form of destructive waves?

A

circular

41
Q

What are the effects of boring molluscs

A

Holes provide weak points for erosion.

41
Q

What happens in the transfers

A

How the sediment moves e.g. longshore drift, swash, ocean currents etc.

41
Q

What are swell waves?

A

Where sea waves, usually during a storm, continue under their own momentum.

41
Q

What are subaerial processes?

A

Weathering and mass movement that alters the shape of the coastline.

41
Q

What are the 4 main erosional processes?

A
  • hydraulic action
  • abrasion
  • attrition
  • corrosion (solution)
41
Q

What is the wave form of constructive waves?

A

Elliptical so it has a strong forward motion.

41
Q

What are offshore bars used for

A

Windfarm
Dredging

Geography (8 decks)

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