2.3 - Coasts Flashcards

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1
Q

What is the size/type of waves controlled by?

A

-wind velocity (speed)
-wind duration (time)
-fetch (product of the first 2)

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2
Q

What is the fetch?

A

-area of contact between the wind and the water, and is where wind-generated waves begin

(friction upon surface causes ripples then waves)

-waves keep growing until limited by wind duration or fetch restriction

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3
Q

Describe destructive waves:

A

-from strong winds (common during winter)

-weak swash, strong backwash
-causes erosion

-shorter wavelength + higher frequency, larger amplitude

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4
Q

Describe constructive waves:

A

-from weak/no winds (common during summer)

-strong swash, weak backwash
-causes deposition

-longer wavelength + lower frequency, smaller amplitude

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5
Q

Name and describe the points of weaknesses (POWs) on a coastline:

A

-bedding planes (gaps between rock layers)
-joints (vertical cracks)
-fault line (a very big joint)

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6
Q

How is a wave-cut platform formed?

A

-waves undercut the foot of a cliff (attacking the POWs by the 4 erosional processes), forming a wave-cut notch

-notch gets larger, unsupported cliff above collapses causing the cliff to retreat over time (cliff increases in height too)

-the gently sloping expanse of rock at the foot of the cliff is the WCP (only exposed at low tide)

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7
Q

Describe the formation of a cave/arch/stack/stump:

A

-wave-cut notch develops at cliff base (by erosional processes at POWs)

-continued erosion causes the sea cave to form (large notch)

-cave eroded through, forms arch

-arch widens at base, roof collapses forming stack

-stack is eroded at base (forming another WCN), collapses, forming a stump

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8
Q

Describe the 2 types of coastline:

A

-discordant, rock types are perpendicular to shore
(can form headlands + bays)

-concordant, rock types are parallel to shore
(can form coves)

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9
Q

Formation of headlands/bays/beaches:

A

-discordant coastline eroded (at POWs by erosional processes), softer rocks eroded quicker and form bays

-bays sheltered from D-waves and have material deposited by longshore drift + C-waves to form beaches

-headlands protrude as the rock type is harder and is more vulnerable to further erosion

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10
Q

What is differential erosion?

A

erosion that occurs at varying rates due to the differences in resistance/hardness of the rock

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11
Q

Describe longshore drift and the motion it causes:

A

the ZIGZAG movement of material along a coast by constructive waves which approach at an angle to the shore (in the direction of the P-wind) but recede at 90 from it

-always draw arrows for P wind and direction of sediment movement

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12
Q

Explain how a spit/bar/tombolo forms:

A

-LSD transports sediment down a coastline, until a change in direction of coastline

-LSD continues to deposit material in a straight line away from coastline, until storm winds create a hook at the end

-bar crosses a section of water, encloses it (lagoon)
-tombolo forms a bridge to an island

Make sure to fully explain LSD and backwash/swash

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13
Q

Name 5 characteristics of a spit:

A

-salt marsh
-hook
-low in height
-attached at one end (although can be bar/tombolo)
-made of sand/shingle (+sand dunes)

(SHLAM)

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14
Q

What do groynes do for a coastal town?

A

-stop erosion and longshore drift to maintain the beach size
-maintains tourism for the beach
-visual pollution
-the larger beach will protect coastal houses

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15
Q

How do coastal sand dunes form?

A

-sand blown by wind further up beach and initially deposits it around an obstacle (rock/plant) and it accumulates, forms an embryo dune

-grows, forms a yellow dune, inhabited by marram grass

-grey dune forms due to increased amount of hummus (soil) from plants in dune

-mature dunes form, can support less specialised plants

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16
Q

What types of coral reefs are there? Describe them and give an example for each:

A

-fringing (close to land and extends out long distances, Tahiti)

-barrier (well defined coral zone separated from land by a shallow sandy bed lagoon, GBR)

-atoll (ring-like formation of reefs with lagoon in the middle, Palmerston)

17
Q

What are the conditions required for coral reefs to form?

A

-warm water (20-28°C)
-shallow (15-25m)
-pH 7-8
-oxygenated water
-no strong upcurrents to damage coral
-unpolluted (Queensland manages waste)

The units given are the ones specific to the Great Barrier Reef case study

18
Q

What is coral?

A

an animal with a symbiotic relationship to the zooxanthellae algae, based on top of a limestone skeleton

19
Q

What is a mangrove?

A

coastal forest in brackish water

Brackish water has more salt than freshwater but not as much as seawater

20
Q

What are the requirements for mangroves to form?

A

-brackish water
-C-waves to deposit sediments
-no strong currents
-in intertidal zone
-tropical climate

21
Q

Give some unique adaptations of mangroves trees:

A

-evergreen + halophytic trees
-aerial roots (support + aids to get oxygen from air during low tide)
-prop roots (support tree in soft sediments)
-sacrificial leaves that excrete excess salt

Too much salt can damage the mangrove trees as it draws water out of its plant cells

22
Q

Give 3 benefits of mangroves:

A

-dissipates storm surge energy which minimises coastal erosion + saves money
-builds soil to elevate coastline
-high biodiversity

23
Q

What are 3 reasons for the removal of mangroves?

A

-agri/aquaculture (shrimp farming)
-firewood
-land for tourists

24
Q

Why is coastal erosion faster in some places than others?

A

-rock type
-amount of POW’s
-wind strength/direction
-sheltering (by wave refraction)

(RAWS)

25
Q

Define corrosion/solution:

A

Small rocks being dissolved by acid/chemicals

26
Q

What do sea walls do?

A

deflect waves

27
Q

What do revetments do?

A

they cause waves to break earlier to minimise erosion to the coastline