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GEOGRAPHY > Coasts > Flashcards

Coasts Flashcards

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1
Q

What causes waves?

A

Transfer of energy from the wind to the sea due to the friction of the wind on the water’s surface

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2
Q

What effects the strength of waves?

A

Speed of wind
Time - how long wind has been blowing
The fetch, maximum distance of open sea the wind can blow over

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3
Q

Characteristic of constructive waves.

Where are they found?
What beaches do they form?
Swash ><Backwash ?

A

Found: Sheltered bays and spits

Low and long

Form sandy beaches

Waves lose energy when in friction with sand so swash is relatively stronger than the backwash so material is deposited.

Low, long wavelengths and low frequency

Build up beaches.

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4
Q

Characteristics of destructive waves

Where are they found?
What beaches do they form?
Swash ><Backwash ?

A

Exposed bays

Pebble beach

High and steep with high frequency

Backwash is stronger than the swash so it removes material from the beach

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5
Q

How do the waves wear away the coast

A

Hydraulic power

Abrasion

Attrition

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6
Q

How does longshore drift occur?

A

Direction of longshore drift is determined by prevailing wind

The swash travells in this direction transporting sediment.

The backwash however moves back at 90 degrees to the beach due to gravity

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7
Q

Why does deposition occur?

A

Water carrying sediment loses energy and slows down.

Occurs when:
Constructive waves are dominant
Large expanses of flat beach so swash spreads out, backwash doesn’t have enough energy to carry sediment back to sea
Where engineered structures like groynes trap material.

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8
Q

What are the two different weathering processes?

A

Mechanical (physical)

Chemical

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9
Q

What is chemical weathering?

A

Chemical reaction when rainwater hits the rock and decomposes or eats it away

Carbonic acid (rain) reacts with rock containing calcium carbonate - limewater
Rocks are then dissolved

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10
Q

What is mechanical weathering

A

Breakdown of rock without changing its chemical composition

Freeze thaw: Water enters cracks in the rocks. Overnight temp drops, the water freezes and expands. Exerting pressure on the rock.
During the day it melts again (thaw)
Repetition causes the cracks in the rocks to break up

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11
Q

What are the types of mass movement?

A

Slumping - A saturated material slumps down a concave slip plane and eotates

Sliding - Material shifts in a straight line along a slide plane

Rockfall - Broken up material along a bedding plane, falls down a slope

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12
Q

What is mass movement?

What factors affect it?

A

Shifting of rocks down a slope when the force of gravity is greater then the force supporting it.

When wet the water acts as a lubricant and makes the material heavier

What’s left behind is a scarp a steep cut in the side of the slope

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13
Q

What is a concordant coastline?

A

Alternating bands of hard and soft rock parallel to the sea

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14
Q

What is a discordant coastline?

A

Alternating bands of hard and soft rock are perpendicular to the coast.

Form headlands and bays. Bays form where the soft unconsolidated material is eroded fast forming a bay with a gentle slope

Headlands form where the hard, consolidated material takes longer to erode so it juts out forming a headland with steep sides.

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15
Q

How does cliffs being eroded form wave cut platforms?

A

Due to preferential erosion (Hydraulic action and Abrasion) at the base of the cliff, between high tide and low tide mark a wave cut notch is formed.

Due to repeated erosion the rock above the notch eventually collapses. Material is washed away.

REPEAT

What is left behind is a wave cut platform - A rocky level of bed rock gently sloping up towards the bottom of the cliff. Represents the base of the old cliff and marks the retreat of the cliff.

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16
Q

How are caves, arches and stacks formed?

A

The hard consolidated rock that makes up a headland often has weaknesses. Joints and faults.

Waves crash into the weaknesses and through erosion (HA + AB) Enlargement of these cracks forces a cave to form.

When the same thing happens on the other side the two caves join to form an arch.

Preferential Erosion from waves and mechanical and chemical weathering continues to wear away the rock until the arch collapses. This forms a stack

16
Q

How are spits formed?

A

Where the is a sharp bend in the coast line eg. river mouth.

Longshore drift transports sand and shingle past the bend and deposits it in the sea. Over time this builds up forming a spit.

Area behind is sheltered from waves so plants are able to grow due to the accumulated material.

17
Q

How do bars form?

A

When two spits join two headlands together this leaves a lagoon behind the bar

18
Q

How are sand dunes formed?

A

When sand deposited by longshore drift it carried up the beach by the wind. Obstacles slow the wind down so it deposits the sand forming small embryo dunes.

As plants grow on the dune the roots stabilise the sand encouraging more sand to be deposited

This then forms foredunes and eventually mature dunes.

19
Q

Hard engineering strategies for coasts

A

Sea walls
Groynes
Gabions
Rock armour

20
Q

Soft engineering strategies for coasts

A

Beach nourishment
Dune regeneration

21
Q

What is a sea wall

P+C

A

Concrete wall that reflects waves back out to sea

Prevents erosion and acts as a flood barrier

Expensive to build and maintain

22
Q

What are gabions?

P+C

A

Wire cage filled with rocks

Absorb wave energy decrease rate of erosion

Ugly

23
Q

What is rock armour?

P+C

A

Big boulders piled against coast

Absorb wave energy so decreases the rate of erosion

They can be moved by waves so need replacing

24
Q

What are groynes?

A

Wooden/ stone fences that prevent longshore drift

Wider beaches - absorb more wave energy and slows them down

Starve beaches further down the coast so increases erosion there

25
Q

What is beach nourishment?

A

Soft engineering strategy involves adding sand and shingle to the beach.

Wider beaches, slows waves.

Expensive and has to be frequently repeated

26
Q

What is sand dune regeneration?

A

Creating or restoring sand dunes by adding sand or plants to stabilise the sand.

Barrier between land and sea. Absorbs wave energy

Protection limited to small area. Nourishment is very expensive

27
Q

What is managed retreat?

A

Remove defences to allow sea to flood land behind it. Which overtime becomes marshland protecting land behind from flooding and erosion.

Cheap and easy

Agricultural land destroyed

28
Q

Why is the Holderness coastline rapidly eroding?

A

Unconsolidated boulder clay, prone to slumping when wet.

Narrow beaches.

Beaches are being starved by Groynes higher up the coast

Long fetch across north sea - powerful waves.

29
Q

What are the coastal management strategies in place on the Holderness coast

A

Hornsea has: Sea wall, Groynes and gabions

Mapleton has groynes however causing conflict in Great Cowden due to increased rate of erosion

30
Q

What are the conflicts on the Holderness coast

A

Great Cowden is experiencing increased rates of erosion due to Mapleton’s groynes

Reduced rates of tourism due to the sea defences

Some people disagree with the placement of sea defences. Protecting settlements over agricultural land/

31
Q

What affects the rate of erosion?

A

Length of fetch
Strength of winds - destructive waves formed
Area under the cliff to act as a buffer and reduce the energy of the waves
Consolidation of rocks and if it has areas of weakness eg. Joints and faults

GEOGRAPHY (16 decks)

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