Enquiry Question 1 - Key Idea 3 Flashcards

Rates of coastal recession and stability depend on lithology and other factors

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1
Q

What is Key Idea 3?

A

Rates of coastal recession and stability depend on lithology and other factors

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2
Q

Meaning of rates of recession:

A

How fast a coastline is moving inland.

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3
Q

What are the three rock types:

A
  • metamorphic
  • igneous
  • sedimentary
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4
Q

Examples of igneous rock

A
  • Granite
  • Basalt
  • Dolerite
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5
Q

Examples of metamorphic rock

A
  • Slate
  • Schist
  • Marble
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6
Q

Examples of sedimentary rock

A
  • Sandstone
  • Limestone
  • Shale
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7
Q

What is the lithology of igneous rock?

A

They are crystalline with interlocking crystals

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8
Q

What is the structure of igneous rock?

A

Rocks such as granite have a few joints so there are limited weaknesses

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9
Q

What is the erosion rate of igneous rock?

A

Very slow. The interlocking crystals make for strong, hard erosion-resistance rock.
Rocks such as granite have few joints, so there are limited weaknesses.

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10
Q

What is the lithology of metamorphic rock?

A

Crystalline. Many exhibit a feature called foliation, where crystals are all orientated in one direction (producing weaknesses)

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11
Q

What is the structure of metamorphic rock?

A

They are often folded and heavily fractured

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12
Q

What is the erosion rate of metamorphic rock?

A

Slow. They are resistant to erosion. Many exhibit a feature called foliation, where crystals are all orientated in one direction (producing weaknesses). They are also often folded and heavily fractured, which are weaknesses that erosion can exploit.

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13
Q

What is the lithology of sedimentary rock?

A

Clastic and are younger than igneous and metamorphic rock.

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14
Q

What is the structure of sedimentary rock?

A

Tend to have many bedding planes and fractures e.g shale. The weakness materials is known to be unconsolidated sediment. However, some limestones and sandstones are actually crystalline sedimentary. They have been compressed and compacted over hundreds of millions years.

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15
Q

What is the erosion rate of sedimentary rock?

A

Moderate - fast. Geologically younger rocks are weaker and therefore erode faster.

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16
Q

Permeable rocks:

A

Allows water to flow through the rock.
- Includes many sandstones and limestones

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17
Q

Impermeable rocks:

A

Do not allow groundwater flow
- Include clays, mudstones, and most igneous and metamorphic rocks

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18
Q

Permeability is important because…

A

groundwater flow through rock layers can weaken rocks by removing the cement that binds sediment in the rock together.
+ can create high pore water pressure within cliffs - affects stability
+ water emerging from below ground onto cliff face at a spring can run down a cliff face and cause surface runoff erosion, weakening the cliff
+ groundwater flow and pore water pressure can cause slumping in unconsolidated sediments on the cliff top

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19
Q

Pore water pressure:

A

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

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20
Q

Why are coasts difficult for vegetation to grow?

A
  • Because coasts are high saline / salty environments so vegetation needs to adapt and it leads to plants becoming inundated
  • There is a lack of hummus (dead, organic materials) so soil lacks nutrients
  • Destructive waves / storms could damage vegetation
  • Erosion can damage plants
21
Q

What is the importance of vegetation at the coast?

A
  • Provides shelter/habitat for organisms (coastal species)
  • Help add nutrients to sand by litter (due to decomposition when the plants lose their leaves and die)
  • Roots of vegetation stabilise sand and soil, reducing the rate of erosion, as landscapes become more stable (roots bind sediment particles together)
  • Prevents flooding by providing a barrier between land and sea
  • When submerged, plants growing in sediment provide and protective layer, the surface of the sediment is not directly exposed to moving water and therefore erosion.
  • Plants protect the sediment from wind erosion by reducing speed at the surface.
22
Q

Pioneer species

A

Highly adaptive to challenging environments. They allow less adapted species to colonise the area creating a climal community.

23
Q

What happens as Pioneer species die

A

They die and drop off organic material, making the soil more nutrient dense, allowing more dense vegetation to grow

24
Q

Plant succession

A

The evolution of plant communities at a sight over time - from pioneer species to climate vegetation

25
Q

Halosere

A

Mud flat / salt marsh environment, inundated

26
Q

Psammosere

A

Sand dune environment, dry

27
Q

Xerophytic

A

Plants adapted to incredibly dry environments with very little nutrients (deep roots, leaves with small surface area to reduce water loss) e.g marram grass which have roots up to 3m deep.

28
Q

Halophytic

A

Plants adapted to survive in environments with high concentrations of salt, thrive in hacoseres. (e.g Samphire)

29
Q

Why is plant succession so important in Haloseres and Psammoseres?

A
  • The roots of pioneer species stabilise the sediment, preventing it from erosion
  • Decomposition of pioneer species allows more nutrients in the soil, allowing for colonisation of less adaptive plant species
30
Q

What are the similarities and differences between the haloseres and psammoseres?

A
  • Halosere environments are inundated whereas psammoseres are very dry
  • Psammosoes have a lack of nutrients whereas haloseres have an abundance of nutrients
  • Both have plant succession occuring
  • Both have coastal accretion
  • Both are in low energy environments
31
Q

Foredune

A

An object such as a plant or rock causes sand to build up on the lee side

32
Q

Mobile dunes

A

Plants begin to bind sand together

33
Q

Semi-fixed dunes

A

The dunes could be 20m high here

34
Q

Explain the formation of embryo dunes

A

Early accumulations of sand at the back shore where dry sand is blown on shore at low tide and accumulates around rocks and wood. these accumulations are prone to wind and wave erosion during storms

35
Q

What are dune slacks

A

At high tide or under storm conditions, sea water may reach dips in the sand dunes, called slacks and collect. blow out caused by strong winds stops when it reaches damp sand at the water table as damp and is less easily blown away.

36
Q

Apart from colour what distinguishes yellow dunes from grey dunes

A

Grey dunes are older with fixed by developing vegetation and have a higher humus content. grey dunes tend to be more acidic. due to the grater vegetation cover and roots from the vegetation mean they are more stable.

37
Q

Why is marram grass important for the formation of sand dunes

A

Effective in stabilising blown sand and acts as a natural buffer to erosion of the areas behind it. flexible waxy leaves which can cope with harsh environment of the coast (water deficient environment). it has roots up to three metres long so can reach water far below the surface and also the anchoring roots provide strength and stabilising properties.

38
Q

Explain why estuaries are ideal for the development of salt marshes (6)

A

They are normally sheltered stretches of water and the lack of strong waves, this encourages the deposition of mud silt. sediment is supplied to an estuary by its river. this is added to by the marine sediment flowing into the estuary at high tide. mudflats are gradually built up in the sheltered water and they will eventually be colonised by the pioneer plants. those plants prosper in the sheltered conditions and help trap more sediment. so the plant succession is set in motion.

39
Q

What is the final stage of salt marsh succession called?

A

Climax Vegatation

40
Q

What is the correct order of plant succession of a sand dune?

A

Embryo dunes, foredunes, yellow dunes, fixed dunes, health/woodland

41
Q

How does vegetation stabilise sediment?

A

As the roots of vegetation bind sediment particles together, stabilising the sand and soil to become more stable, reducing the rate of erosion.
When submerged, plants growing in sediment provide a protective layer, so the surface of the sediment is not directly exposed to moving water and therefore erosion.

42
Q

Sand dune succession formation:

A

1- Begins with colonisation of embryo dunes by pioneer species. They stabilise mobile sand with their root systems.
2- Embryo dunes alter environment conditions from harsh salty mobile sands to environment conditions from harsh salty mobile sands to environment other plants can tolerate
3- New plant species colonise embryo dunes creating foredunes
4- Soil develops, nutrients/water become more available so plants that had better conditions can concieve the area.
5- Dune slacks: periods of raw erosion can create low areas
6- Foredunes become more stabilised and grow to yellow dunes
7- Other species are introduced, e.g marram grass, eventually grey dune forms
8- New embryo dunes form as long as there is a supply of sediment returns, this protects original dune, allowing vegetation.

43
Q

Salt marsh succession:

A

1- Starts in low energy environments, e.g estuaries since they are sheltered from strong waves so sediment can be deposited
2- Algal stage: (e.g blue green algae) grow on and within bare mud, binding it together
3- Pioneer stage: (e.g glasswart) roots begin to stabilise the mud allowing further mud acretion
4- Establishment stage: (e.g Salt marsh grass) a continous carpet of vegetation is established and the salt marsh height increases
5- Stabilisation: (e.g Sea lavender): this area of salt marsh is rarely submerged
6- Climax vegetation: (e.g rush, sedge): developed soil profile and only submerged for x2 each year.

44
Q

Example of Algal stage

A

Blue green algae

45
Q

Example of Pioneer stage

A

Glasswart

46
Q

Example of Establishment stage

A

Salt marsh grass

47
Q

Example of Stabilisation (plant)

A

Sea lavender

48
Q

Example of Climax vegetation

A

Rush, sedge