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Coastal Environments Flashcards

1
Q

How do waves form? (8 steps)

A
  1. The wind blows over the sea
  2. This creates ripples
  3. These ripples that become bigger swells
  4. Swells approach land
  5. The sea becomes shallower
  6. The base of the wave slows due to friction
  7. The top of the wave keeps moving forward & forms a crest
  8. The crest topples, releasing energy, forming a breaking wave
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2
Q

What is wave energy determined by?

A

Wind velocity
Duration of wind
Fetch

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3
Q

What is fetch?

A

The distance the wind blows over the sea

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4
Q

Define swash and backwash:

A

Swash: The movement of a wave up the beach
Backwash: The movement of a wave back down the beach towards the sea

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5
Q

Define the terms wavelength, wave frequency, wave crest, wave trough and wave steepness, wave period and wave energy:

A

Wavelength- the distance between 2 successive crests
Wave frequency- number of waves per minute
Wave crest- highest point of a wave
Wave trough- lowest point of the wave
Wave steepness- the ratio of the wave height to the wavelength
Wave period- the time taken for a wave to travel between one wavelength
Wave energy- a product of wind velocity, duration and fetch

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6
Q

What are the 2 types of waves and their properties?

A

Constructive: created by short fetch, small, low energy, deposit, swash stronger than backwash, 7 per minute

Destructive: created by large fetch, big, high energy, erode, backwash stronger than swash, 14 per minute

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7
Q

Briefly explain wave refraction:

A
  • As waves leave deep water they’re slowed by the frictional drag of contact with the bed
  • Irregular coastlines do not let waves break parallel to the coast, so wave energy is focused on the headlands (orthogonals converge but diverge in bays)
  • Where wave energy is focused and orthogonals converge: a coastline of convergence
  • Here the coastline is exposed to the full energy of the wave so erosion rates will be greatest
  • Opposite to this: divergent zones (bays) will have less energy so deposition occurs
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8
Q

What is a sediment cell?

A

A section of coastline that is involved in the complete cycle of sediment transport and deposition

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9
Q

Define sediment budget, sediment source and sediment sink:

A

Sediment budget: describes the movement of sand sized particles and larger sediment, into and out of a sediment cell

Sediment source: Inputs of sediment

Sediment sink: Outputs of sediment

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10
Q

How many sediment cells are there around the coast of England and Wales?

A

11

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11
Q

What are tides?

A

The regular rising and falling of the surface of the sea

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12
Q

What are tides caused by?

A

The gravitational pull of the sun and moon on the ocean

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13
Q

When the moon is between the Earth and the Sun their combined gravitational pull creates a __________. The tidal range is at its _________.

A

Spring tide- high tide is at its highest and low tides are at their lowest .
Tidal range is at its highest.

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14
Q

When the Earth, moon and Sun form a right angle their gravitational pull interferes with one another giving a _______. The tidal range is at its ______.

A

Neap tide- the lowest high tides and the highest low tides

Tidal range is at its lowest.

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15
Q

What is longshore drift?

A

The zig zag movement of sediment down the beach: the swash carries material up the beach at an angle and then the back wash carries it away in a straight line

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16
Q

What are the 4 types of transportation and their descriptions?

A

Solution- dissolved
Suspension- fine/light material
Saltation- small pebbles bouncing
Traction- large boulders

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17
Q

What is the definition of deposition:

A

The dumping of sediment by the sea- occurs when the waves lose energy.

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18
Q

What are the 2 types of coastline and their definitions?

A 
Concordant coasts: Occur when rock structure is parallel to the coast. Hard bands of rock protect the softer rocks. 
HARD
SOFT
HARD 
SEA

Discordant coasts: Bands of geology are perpendicular to the sea.
HARD SOFT HARD
SEA

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19
Q

What is a headland?

A

An area of hard rock protruding out to sea.

20
Q

What is a bay?

A

An area of soft rock creating an inlet or embayment.

21
Q

How are headlands and bays formed?

A
  • Discordant coastline
  • Soft rock is eroded at a faster rate (by hydraulic action/abrasion) more quickly than hard rock
  • Soft rock retreats creating a bay
  • Hard rock erodes more slowly- stays protruding out to sea
22
Q

Explain the formation of cliffs, wave cut notches and wave cut platforms:

A
  • Waves attack the base of the cliff through the processes of abrasion and hydraulic action
  • Over time the cliff will be undercut and a wave cut notch is formed
  • Eventually the cliff becomes unstable and collapses
  • Further cliff retreat will form a wave cut platform
23
Q

Explain cracks, caves, arches, stacks and stumps:

A
  • Marine erosion enlarges any zones of weakness like joints and fissures
  • Erosion continues to excavate debris and cave forms
  • An arch may form as the cave develops- wave action eventually breaks it through to other side of the cliff
  • When the arch becomes unstable and collapses, a stack forms
  • Continual erosion leads to the formation of a stump
24
Q

Define the terms offshore, nearshore, foreshore and backshore:

A

Offshore: beyond the influence of waves
Nearshore: where the friction with the sea bed causes the waves to slow/break
Foreshore: zone of constant change. Swash and backwash operate here and littoral drift occurs. Berms, ridges and runnels are created by breaking waves and the action of swash and backwash
Backshore: affected by spring high tides that deposit larger calibre sediment here (neap tides don’t reach)

25
What are berms and how are they developed?
- A nearly horizontal plateau on the beach face or backshore - shingle ridges - Formed by the deposition of beach material by wave action- smaller waves with less energy
26
What are ridges and runnels? How are they formed?
Ridges: areas of the foreshore that are raised above the adjacent to the shore Runnels: dips after ridges (think of hills and valleys) Formed by the spreading out of waves energy across a wide area of beach- tends to produce ridges and depressions
27
How are spits formed?
- Swash and backwash in direction of prevailing wind - Change in the shape of the land means longshore drift deposits sediment away from the coastline - Curved end caused by secondary wind - Salt marshes develop behind a spit
28
What is the spit case study?
Hurst Castle spit (Keyhaven marshes behind)
29
How are bars formed?
-When a spit grows across 2 headlands due to deposition of sediment moved by longshore drift, enclosing an area of water called a lagoon
30
How are tombolos formed?
- Where a spit grows away from a headland and links it to an offshore island - Same process as a spit - Island prevents curved laterals as it reaches island before the wind can reach it
31
What are salt marshes?
- Sheltered area behind a spit protected from strong wave action - Plant succession allows it to develop
32
How do salt marshes form? (plant succession)
Mudflats: Algae, eel grass and cordgrass begin to colonise - they must tolerate being submerged for up to 12hours and saline conditions Low Marsh: Mud builds up- seal lavender colonises Vegetation forms a thick mat, hollows that trap sea water High Marsh: Area is covered by spring tides but gradually rises above tidal influence
33
How do salt marshes develop? (summary)
- Start as an accumulation of sand and silt - Deposition builds up sediment in a sheltered part of the coast - Salt tolerant plants colonise - Over time more species develop building up the vegetation
34
Definition of succession:
A sequence of vegetation species that develop within an environment Over time vegetation will develop from small tough plants to large shrubs and trees and as conditions improve more species move into the area
35
What is eustatic and isostatic sea level change?
Eustatic: change in volume of sea water as glaciers/ice caps melt Isostatic: uplift &subsidence of land (weight of ice)
36
What are the impacts of sea level rise?
- 60% of pop live within 60km of the coast - IPCC predicts that the sea level could rise as much as 1m by 2100 - Islands can be affected - Increase in risk of flooding/coastal erosion in UK - Increased cliff/beach erosion - Coastal flooding through inundation/storm surges - Salinisation of farmland/water supply - Destruction of coastal ecosystems and habitats
37
Why is there sea level rise?
- Global warming: as temperatures rise, sea absorbs heat from the atmosphere- it expands and causes sea level rise - Ice sheets are melting faster than the snow is replacing them - Land glaciers are melting - Post glacial rebound: north of UK is rebounding back up as ice sheets are melting
38
What are submergent coastlines and what features do they have?
Stretches along the coast that have been inundated/submerged by the sea due to relative sea level rise Features: Drowned river valleys/rias, drowned glaciated valleys/fjords
39
What are emergent coastlines and what features do they have?
Stretches along the coast that have been exposed due to a fall in sea level (opposite to submergent) Features: Raised beach/machair, wave cut platform, sea cave
40
What and where is Tuvalu?
A Polynesian island nation, located in the Pacific Ocean
41
What are the threats to Tuvalu?
King tides- highest tides, increasing by 5mm a year Storm surges- from the Pacific, flood the land Groundwater flooding- thin, porous coral soil- sea water comes up through pores and contaminates soils
42
What are the environmental impacts of sea level rise in Tuvalu?
- Salt water intrusion affects ecosystems and habitats - Floods/storm surges erode soils- supports less plants and animals - Damage to coral reef- warm temperatures bleach the coral which kills it and the organisms it supports - Beaches are sinking - Floods that used to occur twice a year are occurring every month - Coconut trees swallowed up by sea
43
What are the social impacts of sea level rise in Tuvalu?
- Population forced from their homeland (4000 live in New Zealand) - Families are being separated - Cultures and traditions are dying - family burial plots are having to be moved - Health problems (stress & water borne diseases) are more common - Flooding damages infrastructure and damages water supplies
44
What are the economic impacts of sea level rise in Tuvalu?
- Islands 2 main industries are being hit - Bleaching of coral reef ecosystems reduces fish stocks- hitting fish industry - Salt water intrusion is hitting farmers and agriculture - Cash crops (pulaka) are killed by contaminated groundwater supplies - Downturn in GDP since 2002
45
What are the political impacts of sea level rise in Tuvalu?
- Government has to plan the evacuation/migration of the remaining 10,000 inhabitants - Government is campaigning to try and get its voice heard - Tuvalu relies on aid from New Zealand - Need to campaign to show need to control greenhouse gases

AS Geography (5 decks)

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