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OCR A level Geog p1-Coastal landscape systems > 2.a. Coastal landforms develop due to a variety of interconnected climatic and geomorphic processes > Flashcards

2.a. Coastal landforms develop due to a variety of interconnected climatic and geomorphic processes Flashcards

1
Q

5 different geomorphic processes

A
  • waves
  • aeolian
  • weathering
  • fluvial
  • mass movement
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2
Q

What is weathering

A
  • energy to produce physically or chemicaly altered materials on the surface
  • important for formation of landforms
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3
Q

What is physical/mechanical weathering

A
  • smaller fragments of same rock
  • rock breakdown achieved
  • increasing the exposed surface area of rock=weathering takes place
  • sea prevents air temp dropping from 0°C- reduces some of weathering processes
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4
Q

What is chemical weathering

A
  • chemical reactions between moisture and minerals to decay rock
  • alter chemical and mineral composition
  • residue removed by erosion or transportation
  • rate of reaction icreases with temp- tropical coastlines experience higher rates
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5
Q

What is Van’t Hoff’s Law

A

a 10°c increase in temperature leads to 2.5 times increase in chemical reaction rates

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6
Q

What is biological weathering

A

some physical actions such as plant root growth of chemicals e.g. organic acids

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7
Q

Processes of biological weathering- tree roots

A
  • grow into cracks/joints in rocks and exert outward pressure
  • trees topple, roots can exert leverage on rock and soil, bringing them to surface and exposing further weathing
  • cliff tops/faces
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8
Q

Processes of biological weathering- organic acids

A
  • oa produced during decomposition of plant and animal litter cause soil water to become more acidic and react with some materials (chelation)
  • blue green algae has this effect- producing a shiny film of iron and manganese oxides on rocks
  • shore platforms- malluses secrete acids to produce small hollows in rock
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9
Q

Processes of physical weathering- free thaw

A
  • water enters cracks/joints and expands by nearly 10% when it freezes
  • in confined spaces, this exerts pressure on the rock, causing it to split or pieces to break off, even in very resistent rocks
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10
Q

Processes of physical weathering- pressure release

A
  • when overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface
  • sub surface rocks such as granite
  • paraller fractures sometimes called pseudo-bedding planes
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11
Q

Processes of checmical weathering- carbonation

A
  • rainwater combines with dissolved carbon dioxide from atmosphere to produce a weak carbonic acid
  • this reacts with calcium carbonate in rocks e.g. limestone, to produce calcium bicarbonate (this is soluble)
  • this process is reversible and precipitation of calcite happens during evaporation of calcium rich water in caves
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12
Q

Processes of chemical weathering- hydrolysis

A
  • chemical reactopn between rock minerals and water
  • silicates combine with water, producing secondary minerals e.g. clays
  • Feldspar in granite reacts with hydrogen in water to produce kaolin
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13
Q

Fluvial processes- erosion

A
  • fluvial erosion- main source of a river’s sediment load
  • rivers channel erosion occurring during high flow, high energy events
  • sediment derived from eathering and mass movement processes- result in material moving into river channels
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14
Q

Fluvial processses-transportation

A

-rivers transport sediment by traction, suspension, saltation and solution

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15
Q

Fluvial processes- deposition

A
  • as rivers enter the sea, there is reduction in their velocity as the flowing water moving through the channel enters the static body of sea water
  • available energy reduced, so river’s sediment load is deposited
  • as reduction in energy is progressive, deposition is sequential
  • meeting of fresh water and salt water causes flocculation of clay particles. These clump due to electrical charges between them in saline conditions, and sink to the sea bed
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16
Q

Aeolian processes- erosion

A
  • wind able to pick up sand particles and move them by deflation
  • sand grains moved by surface rolling and saltation
  • carried in suspension which restrics erosion by abrasion to a high of 1m
  • erosive force increases exponentially with increases in wind velocity
  • dry sand is easier for wind to pick up as moisture sticks particles together
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17
Q

Aeolian processes- transportation

A
  • moving air is able to transport material- once particles have been entrained, they can be carried at velocities as low as 20km/hour
  • grains which are too heavy move by surface creep, and the smallest grains are carried in suspension
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18
Q

Aeolian processes- deposition

A
  • material carried by wind will be deposited when the wind speed falls- result of surface friction
  • in coastal areas, this will happen inland
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19
Q

Marine erosion- abrasion

A
  • when waves armed with rock particles scour the coastline, rubbing agaisnt the rock
  • this process acts like sandpaper on wood
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20
Q

Marine erosion- attrition

A
  • when rock particles transported by waves collide

- progressively the coastal rocks become worn away, and are smoother and more rounded

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21
Q

Marine erosion- hydraulic action

A
  • when waves break on a cliff face, the water and air gets trapped in crevices
  • the compression is released when the wave retreats
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22
Q

Marine erosion- pounding

A
  • when the mass of the breaking wave exerts pressure on the rock, causing it to weaken
  • high energy waves exert as much as 30 tonnes per m²
23
Q

Marine erosion- solution

A
  • dissolving of minerals

- the pH of around 7 or 8 means there is little significance unless the local eater id polluted or acidic

24
Q

Marine transportation- suspension

A

-fine materials e.g. clay and sediment are carried by the sea

25
Q

Marine transportation- solution

A

-dissolved minerals are carried by the sea

26
Q

Marine transportation- traction

A

-large boulders and pebbles are rolled long the sea bed

27
Q

Marine transportation- saltation

A

-small stones, pebbles and silt bounces along the sea bed

28
Q

How is sediment moved along the coastline

A

longshore drift

29
Q

Why is material deposited whe water loses velocity or energy

A
  • when rates of sediment accumulation exceeds the rate of removal
  • when waves slow down immediately after breaking
  • at the peak of a wave
  • in law energy environments that are sheltered from the wind and waves
30
Q

Explain the settling velocity

A
  • velocity of water at which sediment particles are deposited
  • as flow velocity decreases, the largest particles being carried out are deposited first
31
Q

When does mass movement occur

A
  • when the force acting on the slope, mostly gravity, exceed the forces trying to keep the material on the slope, mostly friction
  • when a mass movement event occurs, potential energy has been released
  • most significant mass movement processes are those that act on cliffs and add rocks to the sediment budget
32
Q

Forms of mass movement- rock fall

A
  • on cliffs of 40° or more, especially where the cliff face is bare and rocks become detached through mechanical weathering processes
  • gravity causes these rocks to fall to the foot of the cliffs and wave processes often remove them
33
Q

Forms of mass movement- slides

A
  • occur on more horizontal levels and along a fault or bedding plane
  • wave processes erode material at the base of the cliff
34
Q

EROSION LANDFORM- How is a wave cut notch and steep cliff profile formed

A
  • destructive waves breaking repeatedly on steep coastlines
  • this undercuts between the high and low tide mark (creates wave cut notch)
  • continued undercutting causes mass movement and creates a steep cliff profile. The cliff retreates inland, parallel to the coast. Cliff profiles influenced by their geology
35
Q

EROSION LANDFORM- How is a shore platform formed

A
  • as undeructting continues, the cliff becomes higher and a gently sloping shore platform is cut from the solid rock at the base of a cliff
  • shore platforms are often deeply dissected by abrasion, due to the large amount of rock debris being dragged across the surface
  • as shore platformbecomes wider, shallow water means friction with waves slows them down- reudes energy and the rate of undercutting
36
Q

EROSION LANDFORM- Example of a cliff and shore platform

A

Kimmeridge Bay in Dorset

37
Q

EROSION LANDFORM- What are geos and how is it formed

A
  • narrow steep sided inlets of the coastline
  • form by eroding vertical joints and faults in the geology
  • hydraulic action is influential in forming them
  • example- Huntsman Leap which is a 35m deep geo
38
Q

EROSION LANDFORM- How are blowholes formed

A
  • when geos form as tunnel-like caves that run at 90° to the cliff line
  • sometimes they suffer from roof collapse after continued erosion forming a geo
  • if a vertical fault along the roof of a cave weakens and collapses, then a glow hole will have formed
  • storms means large waves are funnelled through the cave and blasted out the blowhole
39
Q

DEPOSITION LANDFORM- What are spits and how are they formed

A
  • long, narrow beaches of sand or shings that are attached to the land at one end and stretch across a bay or estuary at the other
  • generally formed by longshore drift, occurring in one dominant direction, which carries material to end of beach
  • storms build up larger material so makes spits more permanent
40
Q

DEPOSITION LANDFORM- How does wave refraction and secondary wind/wave directions affect the spit

A
  • causes the end of the spit to recurve
  • this can take place several times- spit ends up with multiple recurved featues
  • if a spit forms across an estuary, its growth may be limited by the influence of a rivers current
41
Q

DEPOSITION LANDFORM- Example of a spit- Orford Ness in East Anglia

A
  • north easterly prevailing wind result in longshore drift movement from north to south
  • spit had formed across the estuary at the River Ore but river’s current has stopped it from joining with the coastline on the opposite side
42
Q

EROSION LANDOFORM- how are headlands and bays formed

A
  • form where there are bands of different rock with different resistance to erosion
  • where these bands of rock lie perpendicular to the coastline, the weaker rock erodes more quickly forming a bay, and the hard rock is left as a headland (discordant coastline)
  • where the bands of rock lie parallel to the coastline, the hard rock lies on the seaward side of the coastline and bays develop when a weakness is eroded landwrd (concordant coastline)
  • example- Isle of Purbeck
43
Q

EROSION LANDFORM- how are caves, arches, stacks and stumps formed

A

1) weaknesses e.g. joint in a redistant rock e.g. chalk are attacked by waves
2) erosion widebs the weakness and undercuts the base to form a cave
3) erosion processes concentrate on the headland. Often a cave meets another and a hole through the headland is opened up to form an arch
4) as cliff face recedes, a wave cut platform develops. Arch eventually collapses leaving an isolated stack
5) sea attacks base of stack. Eventually a wave cut notch will udercut the stack and a raised portion of the wave cut platfrorm will be left as a stump
EXAMPLE- OLD HARRY ROCKS

44
Q

DEPOSITION LANDFORMS- how are beaches formed

A
  • formed by the accumulation of sand and shingle deposited by high and low tides
  • features- cusps, ripples
  • beaches are dynamic and will change according to wind strength
  • equilibrium profile develops with a balance between erosion and deposition
45
Q

DEPOSITION LANDFORMS- what are tombolos and how are they formed

A
  • beaches that connect the mainland to an offshore island
  • formed from spits that have continued to grow seawards until they reach to join an island
  • thought the 30km long shingle beach at Chesil was formed this way- eastern end, flinty pebbles, western end, smaller pea sized shingle. Strong longshore currents have moved sediments from all sizes eastwards
46
Q

DEPOSITION LANDFORMS- how are onshore bars formed

A
  • develop if a spit continues to grow cross an indentattion, and there is no strong flow of water from the landward side
  • 100m wide bar at Slapton Sands in Devon may have been formed in this way. However no dominant direction of longshore drift on east facing coastline. This feature may have been formed by onshore movement during the post glacial sea level rise
47
Q

Deposition LANDFORM- what are salt marshes

A
  • features of low energy environments on the landward side of spits
  • UK gas 45,500 ha of salt marsh (eastern/northwest England)
  • vegetated reas of deposited silts and clays
  • subjected twice daily
  • stems and leaved trapsediment while roots stabilise the sediment
  • form a flat landscape in low lying estuarine areas
  • rates of 10cm per year
48
Q

DEPOSITION LANDFORM- how are salt marshes form

A

1) pioner specied develop (halophytes- salt tolerant). Ecology- glasswort which slows he movement of water and encorage stabilisation
2) soil develops, lower slinity, current sloes, more deposition, orgamic matter produced. The marsh increases in height. Biodiversity and plant cover increase. Ecology- sea aster, sea lavender
3) mud level rises, land rises above sea level, rushes and reeds grown. Salinity levels fall and soil develops. Ecology- climax vegetation: ash

49
Q

DEPOSITION LANDFORM- deltas- what are they

A
  • large areas of sediment found at the mouths of many rivers

- deltatic sediments are deposited by rivers and tidal currents

50
Q

DEPOSITION LANDFORM- deltas- how do they form

A
  • when rivers entering the sea are carrying large sediment loads
  • where a broad continental shelf margin exists at the river mouth to provide a platform for sediment accumulation
  • when low energy environments exist in the coastal area
51
Q

DEPOSITION LANDFORM- deltas- what is their structure

A
  • submergd delta plain- lies below mean low water marks. Is composed of marine sediments
  • lower delta plain- intertidal zone and composed or river/marine deposits
  • upper delta plain- furthest inland, and composed of river deposits
52
Q

DEPOSITION LANDFORM- deltas- distributaries

A
  • they are crissed crossed by distributaries
  • deposition in the channel forms bars, causes channel to split into two
  • channels lined with levèes
  • flood means natural enbarkments are breaches and sediment deposition takes place in crevasse splays
53
Q

DEPOSITION LANDFORM- deltas- different types

A
  • cuspate- pointed extension to the costline and occurs when sedimen accumulate
  • artcuate- sufficient sediment supply is available for delta to grow seawards. Wave action can smooth its edge
  • birds food- distributaries built out from coast in branching pattern

OCR A level Geog p1-Coastal landscape systems (9 decks)

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