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geography > Geology and the coast > Flashcards

Geology and the coast Flashcards

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1
Q

Definition of strata

A

layers of rock

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2
Q

Definition of bedding planes (horizontal cracks)

A

natural breaks in strata caused by gaps in time during periods of rock formation

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3
Q

Definition of joints (vertical cracks)

A

fractures caused by contraction as sediments dry out/ earth movement during uplift

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4
Q

Definition of faults

A

major fractures in rock produced by tectonic forces

-faults then move along fault planes

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5
Q

Definition of dip

A

the angle at which rock strata is

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6
Q

Definition of lithology

A

physical characteristics of particular rocks

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7
Q

Definition of coastal morphology

A

shape and form of coastal landscape and their features

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8
Q

Definition of coastal recession

A

another term for coastal erosion

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9
Q

What produces concordant and discordant coasts

A

geological structure

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10
Q

What is a concordant coastline

A

where bands of more-resistant and less-resistant rock run parallel to the coastline

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11
Q

When do concordant coastlines form

A
  • when rock strata runs parallel to the coast
  • outer hard rocks acts as a protective barrier to erosion of the softer rocks further inland
  • Sometimes outer hard rock is punctured- allowing sea to erode the softer rocks
  • cove is produced (a circular area of water with a relatively narrow entrance from the sea)
  • dalmatian
  • haff
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12
Q

Definition of deformation

A

the degree of tilting or folding of rock.

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13
Q

The Isle of Purbeck’s southern coast is a concordant coastline. Explain how Lulworth Cove has been formed

A
  • outer hard rocks acts as a protective barrier to erosion of the softer rocks further inland
  • outer hard rock is punctured- allowing sea to erode the softer rocks
  • cove is produced (a circular area of water with a relatively narrow entrance from the sea)
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14
Q

Name the 3 types of concordant coastlines

A
  • dalmatian coasts
  • haff coasts
  • south dorset coast
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15
Q

How did the Dalmatian coast become a concordant coastline

A
  • Geology is limestone
  • folded by tectonic activity into series of anticlines and synclines- parallel to coastline
  • drowned by rising sea levels creating
    concordant coastline
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16
Q

How did Lulworth Cove become a concordant coastline

A
  • The outer hard rock is limestone
  • less resistant clay and limestone behind portland limestone
  • sea has broken through barrier of portland in parts and eroded clays behind it
  • This has allowed the formation of a cove
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17
Q

Name the concordant features found at haff coastlines

A

-long spits of sand and lagoons- parallel to coast

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18
Q

What is a discordant coastline

A

where bands of more-resistant rock and less-resistant rock run at right angles to the coast

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19
Q

When do discordant coastlines form

A

when different rock strata intersect the coast at an angle

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20
Q

Why are discordant coastlines dominated by headlands and bays

A

less resistant rock erodes rapidly to form bays

more resistant rock erodes slowly, leaving headlands

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21
Q

Why is there little erosion at discordant coastlines

A
  • In deep water wave crests are parallel

 As waves approach the shallow water offshore of a headland they slow down and wave height increases

 In bays, wave crests curve to fill the bay and wave height decreases

 The straight wave crests refract, becoming curved, spreading into out in bays and concentrating on headlands

 The overall effect of wave refraction is to concentrate powerful waves at headlands (meaning greater erosion) and create lower, diverging wave crests at bays, reducing erosion

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22
Q

Give two examples of discordant coastlines

A
  • Dorset Coastline

- West Cork coast of Ireland

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23
Q

How did West Cork coast of Ireland become a discordant coastline

A
  • Rock strata that include: Limestone,
    Mudstone and sandstone meet the

coastline 90 degrees in parallel bands
- Weak rocks have been eroded, creating
elongated, narrow bays, whereas more-
resistant rocks for headlands

  • Especially resistant areas remain as
    detached islands
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24
Q

How did Dorset Coastline become a discordant coastline

A

The limestone is resistant to erosion; then
to the north at Swanage bay the rock

type is softer greensand
- North of Swanage, the chalk outcrop
creates the headland which includes Old
Harry Rocks

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25
Q

What 2 characteristics influence cliff profiles

A
  • resistance to erosion of the rock

- dip of rock strata in relation to the coastlin

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26
Q

What 3 geological features influence cliff profiles

A
  • faults
  • joints
  • fissures
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27
Q

What is differential erosion

A

When different types of rocks are eroded at different rates

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28
Q

What type of cliff profile does horizontal dip produce

A

-vertical/ near vertical profile

with notches reflecting strata that are more easily eroded

29
Q

What type of cliff profile does seaward dip, high angle produce

A
  • sloping, low angle profile
  • with one rock layer facing sea
  • vulnerable to rock slides down dip slope
30
Q

What type of cliff profile does seaward dip, low angle produce

A
  • profile may exceed 90 degrees
  • producing overhanging rock
  • very vulnerable to rock falls
31
Q

What type of cliff profile does seaward dip, landward dip produce

A
  • steep profiles of 70-80 degrees

- producing very stable cliff with reduced rock falls

32
Q

What controls the location of microfeatures

A

the location of faults and/ or strata which have a high density of joints and fissures

33
Q

Explain how faulting influences the features of a Cliff profile

A
  • Represents major weaknesses within rock
    layers (cracks in crust)
  • Either side of a fault line, rocks are often
    heavily fractured and broken and these
    weaknesses are exploited by marine
    erosion
34
Q

Explain how jointing influences the features of a Cliff profile

A
  • Occur in most rocks, often in regular
    patterns, dividing rock strata up into

blocks with a regular shape

35
Q

Explain how Folding influences the features of a Cliff profile

A
  • Folding occurs due to crust compression
  • Horizontal strata can be folded into a

series anticlines and synclines

36
Q

When do headlands and bays form

A

when rocks of different strengths are exposed at the coast

37
Q

What are folds and what are they produced by

A

bends in rocks

-produced by sedimentary rock layers being squeezed by tectonic forces

38
Q

What are the 2 main types of folds

A

anticlines and synclines

39
Q

Why are folds more easily eroded

A

Folded rock is often more heavily fissured and jointed

40
Q

What is unconsolidated sediment

A

material such as sand, gravel, clay, silt

that are loose and easily eroded- haven’t been compacted

41
Q

Name 2 geological factors affecting coastal erosion

A

lithology- soft rock type, weak cohesive bonds, porous rocks

geological structure- well jointed rocks, seaward dipping beds, heavily faulted rocks

42
Q

Name 3 characteristics of igneous rocks

-give one example of this type of rock

A
  • erode very slowly
  • crystalline -> interlocking crystals -> resistant rocks
  • impermeable
  • > granite
43
Q

Name 4 characteristics of metamorphic rocks

-give one example of this type of rock

A
  • erode slowly
  • crytalline -> hard and resistant
  • many exhibit feauture called foliation -> crystals orientated in one direction - produces weaknesses
  • Often heavily folded and faulted
  • > slate
44
Q

Name 4 characteristics of sedimentary rocks

-give one example of this type of rock

A
  • erode moderately to fast
  • clastic
  • weak bedding planes
  • heavily jointed -> formed by the compaction and cementation of deposited material
  • younger rocks
45
Q

Name 3 ways lithology affects the resistance of rocks

A
  • mineral composition -> some rocks contain reactive minearls- chemically wetahered -> some are inert -> slowly chemically wetahered
  • rock class -> igneous, sedimentary, metamorphic
  • structure -> fissures, joints, faults, air spaces (porous) erode quicker
46
Q

Why are older rocks more resistant than younger rocks

A

Older rock- buried deeper -> more intense compaction -> stronger sedimentation -> more resistant than younger rocks

47
Q

What is differential erosion

A
48
Q

Explain how complex cliff profiles are formed

A
  • formed where cliffs are made of strata of differing lithology
  • composite cliffs with diff rock layers
49
Q

What is pore water pressure

A

pressure water experiences at a particular point below water table due to weight of water above it

50
Q

What can complex cliff profiles be influenced by

A
  • permeablity of strata
  • permeable rocks allow water to flow through them
  • impermeable rocks don’t allow water to flow through them
51
Q

Name the 4 stages that occur in the erosion of complex cliff profiles

A

1) spring creating erosion
2) Groundwater flow removing cement
3) Pore water pressure -> slumping and sliding
4) Saturation -> slumping and sliding

52
Q

Explain the stages that occur in terms of erosion that [produces complex cliff profiles

A
  • permeable rock overlays impermeable rock -> groundwater unable go down into impermeable roc
  • water flows along impermeable rock weakening it (removes cement binding rock) -> slumping
  • also produces pore water pressure -> pushes rock particles apart -> affects stability

-surface run off erosion -> groundwtaer emerges onto cliff face

  • Saturation promotes mass movement -> adds weight.
  • > slumping and sliding producing a complex cliff profile.
53
Q

Name the 2 main types of cliff profile

A

-steep, unvegetated cliffs ->
where marine erosion dominates -> steep profile -> active undercutting ->
little/ no debris at base -> broken up by attrition, transported offshore/ along coast

Shallow-angled, vegetated cliffs -> sub-aerial process dominated -> curved slope profile -> lower angle face
-> debris at the base- sub-aerial processes (weathering, mass movement, surface run-off erosion) slowly move sediment downslope, but marine erosion is unable to remove it from base
produced

54
Q

What are the three types of coastal vegetation that can protect a coastline from erosion

A
  • Coastal sand dunes
  • Coastal salt marshes, found in many river estuaries
  • Coastal mangrove swamps
55
Q

How does vegetation stabilise sediment, slowing erosion

A

roots of plants bind sediment particles -> stronger

  • submerged plants growing in sediment -> protective layer -> surface not exposed to moving water
  • plants protect sediment -> reducing wind speed at surface -> friction w vegetation -> reducing wind erosion
56
Q

What are Halophytes

A

Plants -> tolerate salt water,

around their roots/ being submerged at high tide/ salt spray from the sea

57
Q

What are Xerophytes

A

Plants -> tolerate very dry conditions

e.g found on coastal sand dunes where sandy soil retains very little water due to drainage

58
Q

What is Plant succession

A

changing structure of plant community over time as an area of initially bare sediment is colonised.

59
Q

What are pioneer plants

A

first plants to colonise freshly deposited sediment

60
Q

What 3 steps do embryo dune pioneer plants initally do to begin first stage of plant succession

what does this allow?

A

modify the environment:

  • Stabilising sediment
  • reduce wind speed at sand surface -> more sand deposited
  • Add dead organic matter -> that retains moisture, contributes nutrients and provides shade
  • alters harsh, salty sand -> environment other plants can tolerate
61
Q

What occurs after the pioneer species have successfully modified the environment

A

new plant species colonise the embryo dune -> creating fore dune

-as environment changes overtime -> diff species colonise until its stable

62
Q

What is (climatic) climax community

A

The end result of plant succession when final community are adjusted to climatic conditions of area

63
Q

Explain the timeline of plant succession

A
  • embryo dunes -> dry sand
  • fore dunes -> sea rocket
  • yellow dunes -> marram grass
  • grey dunes -> low shrubs
  • dune slack -> aquatic plants
  • woodland -> pines
64
Q

What is plant succession on sand known as

A

psammosere

65
Q

Explain the 7 steps that occur during Psammosere

A

1) embryo dunes form _> barrier/ shelter forms -> trap sand
2) embryo grows -> colonised- xerophytic pioneer plants -> alter conditions
3) Pioneer plants stabilise sand-> marram grass colonises
4) dune grows rapidly -> yellow dune
5) marram grass dies -> adds hummus to sand -> grey dune
6) dune -> above sea level -> soil has nutrients -> non-xerophytic plants colonise
7) climax plant community -reached

66
Q

What are salt marshes

A

areas of flat silty sediments that accumulate around estuaries or lagoons

67
Q

Explain the 7 steps that occur during Halosere

?do i need to know seral stages

A

1) fresh water, sea water mix -> clay particles stick together and sink -> flocculation
2) Blue-green algae, gut weed grow and bind mud,
3) roots stablise mud -> mud accretion
4) continous carpet of vegetation established -> salt marsh height increases
5) area of salt marsh -> rarely submerged
6) Rainwater washes salt out of the high marsh’s soil, allowing land plants to colonise.
7) continues until climax community is reached.

68
Q

Where do salt marshes develop

A
  • sheltered areas
  • where salt, fresh water meet
  • no strong tides

geography (55 decks)

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