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Geography - B - Coastal Landscapes > Block 5 (Processes Of Coastal Weathering, Mass Movement, Erosion + The Characteristics + Formation Of Associated Landforms + Landscapes) > Flashcards

Block 5 (Processes Of Coastal Weathering, Mass Movement, Erosion + The Characteristics + Formation Of Associated Landforms + Landscapes) Flashcards

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1
Q

What are sub-aerial processes?

A

Land-based processes that alter the shape of the coastline

  • Weathering
  • Mass movement
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2
Q

What is weathering?

A

The breakdown or changing of rocks at the Earth’s surface, in situ

  • Biological/biotic
  • Chemical
  • Physical/mechanical
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3
Q

What is biological/biotic weathering?

A

The breakdown of rock caused by plants + animals

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4
Q

How can plants complete biological/biotic weathering?

A
  • Roots can open up faults in the rock

- This increases the rock’s vulnerability to destructive processes (e.g hydraulic action)

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5
Q

How can animals complete biological/biotic weathering?

A
  • Burrowing animals can weaken soft rocks
  • Animals can hive off chemicals that contribute to chemical weathering (chelation) - e.g. seagull guano is very acidic, and can break down calcium carbonates, limestone, chalk etc.
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6
Q

How can humans complete biological/biotic weathering?

A
  • Humans walking on rocks, etc, can break them down over time
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7
Q

What is chemical weathering?

A

The breakdown of rock caused by a change in its mineral composition

  • Solution
  • Hydration
  • Hydrolysis
  • Oxidation/reduction
  • Chelation
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8
Q

How does solution complete chemical weathering?

A

Certain minerals are dissolved by acidic water (acids in seawater + acid rain)
- E.g. Limestone dissolved easily by carbonic acid via ‘carbonation’

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9
Q

How does hydration complete chemical weathering?

A

Absorption of water by rock weakens its crystal structure, making it more susceptible to other weathering

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10
Q

How does hydrolysis complete chemical weathering?

A

Water reacts with minerals in rock - causing changes related to hydrogen ion concentration
- E.g. Feldspar minerals in granite are very affected by these changes

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11
Q

How does oxidation/reduction complete chemical weathering?

A

Oxidation - rocks gain oxygen
Reduction - rocks lose oxygen

  • E.g. Oxidation - (oxygen from water - mainly affects rocks with high ion concentration)
    Reduction - common in waterlogged conditions (less oxygen)
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12
Q

How does chelation cause chemical weathering?

A

Organic acids bind to metal ions, causing breakdown of rock

- E.g. Acids from plant roots + decaying animals

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13
Q

What is physical weathering?

A

The breakdown of rock by water + the environment, without a change in chemical composition

  • Salt water crystal growth
  • Freeze-thaw
  • Wetting + drying
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14
Q

How does salt water crystal growth complete physical weathering?

A

Salt left in cracks in rocks when seawater evaporates. Crystals grow, exerting pressure on rock + causing its breakdown.

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15
Q

How does freeze-thaw complete chemical weathering?

A

Repeated freezing + thawing causes ice crystal growth. Ice crystals exert pressure on rock, causing its breakdown.

  • Common in high latitude areas (cold) + in rocks with lots of faults
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16
Q

How does wetting + drying complete physical weathering?

A

Minerals repeatedly expand (wet) + contract (dry), causing outer layers to break off.

(Also known as ‘onion-skin weathering’)
- Common in clays

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17
Q

What are mass movements?

A

Downslope movement of material under influence of gravity

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18
Q

What are 5 things that affect mass movement?

A
  • Lithology - soft/hard rock, e.g clay is soft so slumps
  • Structural geology - bedding planes, steeper is weaker
  • Weathering - loose material from weathering makes cliff weaker
  • Vegetation - less veg makes cliff weaker, not held together
  • Water in cliff - more makes it heavier, weaker
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19
Q

What are the 4 rapid mass movements?

A
  • Rock fall (FASTEST)
  • Rock slides
  • Rock toppling
  • Rotational slides + slumps
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20
Q

What are the 2 slow mass movements?

A
  • Creep (SLOWEST)

- Solifluction

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21
Q

How does mass movement happen through rock fall?

A

Blocks of rock, loosened by weathering, fall to cliff face

  • Often when bedding planes are vertical
  • E.g. Svalbard - rocks loosened by freeze-thaw
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22
Q

How does mass movement happen by rock slides?

A

Blocks of rock slide down cliff face

  • Often when bedding planes are tilted backwards
  • E.g. Gower Peninsula - limestone cliffs
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23
Q

How does mass movement happen through rock toppling?

A

Whole columns/blocks of rock fall seawards

- E.g. Giant’s Causeway - columnar basalt

24
Q

How does mass movement happen through rotational slides/slumps?

A

Sections of cliff give way along a concave slip surface, leaving fallen material as visible mass until eroded

  • Often when bedding planes are tilted backwards/concave
  • Often when permeable overlays impermeable rock, so rock becomes saturated and lubricated slip plane forms
  • E.g. Barton on Sea
25
Q

How does creep cause mass movement?

A 
Extremely low (1-3mm per year) downslope movement of regolith (loose material) 
- Almost imperceptible - seen by tilted fences + poles
26
Q

How does mass movement happen through solifluction?

A

Slow downslope movement of regolith that is saturated by melting of active layer above permafrost
- E.g. In summer of periglacial regions (UK may have had this after Ice Age)

27
Q

What are marine processes?

A

Processes associated with the action of waves

  • Erosion
  • Transportation
  • Deposition
28
Q

What is erosion?

A

The wearing away and/or removal of material (rock)

  • Hydraulic action
  • Abrasion/corrasion
  • Solution/corrosion
  • Attrition
29
Q

How does erosion happen through hydraulic action?

A

Waves break against coast, entering rock faults + applying great pressure on air inside. Waves then retreat + pressure released with explosive force. Mini explosions break rock, which is removed by waves.

  • Common in rock with many joints/faults - e.g. limestone
30
Q

How does erosion happen through abrasion/corrasion?

A

Material carried by waves is thrown against cliff face, breaking down and removing the rock

  • Common in high energy conditions, e.g storms
31
Q

How does erosion happen by solution/corrosion?

A

Salt water (+ acids within it, e.g from waste) can slowly dissolve + remove rock on coastline

  • Common in carbonates that are soluble in slightly acidic water, e.g limestone + chalk
32
Q

How does erosion happen by attrition?

A

Weathered material carried by waves hit into each other, becoming increasingly smaller + smoother

  • Breaks down material carried by waves, NOT coastline
33
Q

What is a cliff? Give an example

A

A steep rock face, common next to the Sea

  • E.g resistant - Cliffs of Moher, Ireland
  • E.g less resistant - Holderness Coast, England
34
Q

How does a cliff form?

A
  • Destructive waves attack base (mainly ha+abrasion), forming wave cut notch
  • Cliff becomes undercut + unsupported
  • Concordant coastline
  • Weathering from above + notch enlarged, until gravity causes rock collapse
  • Steep cliff face left, with old cliff base as smooth wave cut platform
  • Cliffs continuously retreat + are shaped through erosion, weathering, mass movement
35
Q

How are cliffs affected by geology?

A

More resistant geology forms tall, steep cliffs
- Harder rock
- Insoluble
- Permeable
- Few joints, bedding planes, faults, folds (weaknesses)
(E.g. Cliffs of Moher - Ireland)
Less resistant geology forms small, gentle cliffs
- Softer rock
- Soluble
- Impermeable
- Many joints, bedding planes, faults, folds (weaknesses)
(E.g. Holderness Coast - receding fastest in EU, by 2m/yr)

36
Q

What is a headland? Give an example

A

Point of land (often high) that extends out into body of water

  • E.g Ballard Point, Dorset Coast
37
Q

What is a bay? Give an example

A

An inlet of the sea where land curves inwards, usually with a beach

  • E.g Swanage Bay, Dorset Coast
38
Q

How do headlands and bays form?

A
  • Discordant coastline
  • More resistant rock erodes slower (forming headlands)
  • Less resistant rock erodes faster (forming bays)
  • After formation, wave refraction reverses erosion rates (converging orthogonals increase erosion of headlands, diverging orthogonals decrease erosion of bays)
39
Q

How are headlands + bays affected by geology?

A
  • Always form on discordant coastline - with rocks of contrasting resistance running perpendicular to coast
40
Q

What is a cave? Give an example

A

Natural opening in the rock

  • E.g caves at Durlston Head, Dorset Coast
41
Q

What is an arch? Give an example

A

A cave that extends through the headland

  • E.g Durdle Door, Dorset Coast
42
Q

What is a stack? Give an example

A

Detached pillar of rock located off a headland

-E.g Old Harry, located off Ballard Point (Dorset Coast) - headland folded by tectonics 65 mill yrs ago made line of weakness to start sequence

43
Q

What is a stump? Give an example

A

Collapsed stack that is less than half the height of the original cliff

  • E.g Old Harry’s Wife, Dorset Coast
44
Q

How does a CASS system form?

A
  • Line of weakness (e.g. fault) enlargened by erosion (e.g. ha)
  • Crack grows to cave, as destructive waves converge on headland
  • Cave grows from wave refraction + may form back to back
  • Waves break through headland to form arch
  • Weathering attacks top of arch, waves attack base, weakening it
  • Top of arch collapses to leave detached stack
  • Waves attack base of stack
  • Stack eventually becomes too unstable + falls to leave stump
45
Q

How are CASS systems affected by geology?

A
  • Rock must be resistant (as headland needed)
  • Rock must have some lines of weakness (e.g faults) that can be exploited by destructive waves during wave refraction to start sequence
46
Q

Does the CASS system always form in a linear order?

A

No

47
Q

Give an example of the rocks involved in a headland/bay system

A
  • Bagshot beds (less resistant)
  • Chalk (more resistant)
  • Wealdon clays + greensands (less resistant)
  • Purbeck + portland limestone (more resistant)
48
Q

What is a wave cut platform? Give an example

A

Wide, horizontal/gentle sloping section of rock (that was once the cliff base) backed by cliffs

-E.g Nash Point, South Wales

49
Q

How are wave cut platforms formed?

A
  • Waves attack base of cliff
  • Wave cut notch (indent) formed at high tide mark
  • Over time, notch enlargenedl, undercutting cliff
  • Cliff becomes unstable + collapses
  • Wave cut platform left, smoothened over time by abrasion
  • Process continues, causing cliff retreat + growing platform
50
Q

How are wave cut platforms affected by geology?

A
  • Rock is resistant - must be able to be undercut without crumbling
51
Q

What is a geo? Give an example

A

Deep inlet in a cliff face

-E.g Sclaits Geo, Scotland

52
Q

How do geos form (2 ways)?

A
  • Line of weakness is exposed to significant erosion + widened
  • Roof of a sea cave collapses
53
Q

How are geos affected by geology?

A
  • If formed from erosion, must have a line of weakness (e.g fault)
54
Q

What is a blowhole? Give an example

A

Opening in ground connected to underground cave system, out of which water is forced

  • E.g Kiama Blowhole, New South Wales, Australia - can spray 50L of water 25m into air, accompanies by Little Blowhole
55
Q

How are blowholes formed?

A
  • Sea cave exposed to erosion
  • Vertical line of weakness in cave exploited + widened to form small blowhole
  • Water forced up through blowhole, due to pressure difference between large cave + small blowhole
56
Q

How are blowholes affected by geology?

A
  • Must have vertical line of weakness within cave
57
Q

What are the 6 landforms of erosion?

A
  • Cliffs
  • Headlands + bays
  • CASS sequences
  • Wavecut platforms
  • Geos
  • Blowholes

Geography - B - Coastal Landscapes (10 decks)

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