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Geography > Coastal environments > Flashcards

Coastal environments Flashcards

1
Q

Fetch

A

Length of time and distance over open water that the wind has blown to create a wave

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2
Q

Features of constructive waves

A
  • Long wavelength
  • Shallow gradient waves
  • Strong swash
  • Weak backwash
  • Deposition of material
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3
Q

Features of destructive waves

A
  • Steep gradient waves
  • Tall waves with short wavelength
  • Weak swash
  • Strong backwash
  • Erosion of material
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4
Q

Hydraulic action

A

Waves hit cliffs and force air into cracks

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5
Q

Abrasion

A

Waves pick up pebbles and hurl them against the cliff

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6
Q

Solution

A

The dissolving of soft rocks by the sea

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7
Q

Attrition

A

Pebbles carried by waves collide with each other and become smaller and more rounded over time

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8
Q

Deposition

A

Occurs when waves lose energy/material carried is too large to transport with the amount of energy the wave has

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9
Q

Longshore drift

A
  • Wave swash approaches beach at an angle (the same direction as the prevailing wind)
  • Backwash is at a 90-degree angle due to gravity
  • Process repeats, moving sediment along the beach
  • Smaller material is transported further as it requires less energy
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10
Q

Solution

A

When minerals in rocks like chalk and limestone are dissolved in seawater and carried within. The load is not visible

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11
Q

Suspension

A

Small particles such as silts and clay are in the flow of the water

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12
Q

Saltation

A

Where small pieces of shingles or large sand grains are bounced along the sea bed

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13
Q

Traction

A

Where pebbles and larger material are rolled along the sea bed

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14
Q

Weathering

A

The breaking down of rocks and other materials in situ

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15
Q

Mechanical weathering

A

Processes such as freeze-thaw, salt crystal growth, and wetting and drying of clay rich rocks

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16
Q

Biological weathering

A

When rocks are broken down by things such as plant roots, burrowing animals and nesting birds

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17
Q

Chemical weathering

A

Processes such as carbonation, oxidation and acid rain

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18
Q

Slumping

A

Waves erode the cliff base and cause instability. Rainwater permeates through the rock, saturating it, until it becomes unstable and slumps along bedding planes. Leads to a stepped appearance to the cliff

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19
Q

Sliding

A

Weathering loosens rock, which slides down off bedding planes. Leads to landslides and mudslides

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20
Q

Geology

A

Rock type e.g. granite or chalk

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21
Q

Lithology

A

Characteristics of the rock e.g. relative hardness and permeability

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22
Q

Discordant geology

A

Rock outcrops are at 90 degrees to the sea, leading to headlands and bays where there are bands of soft and hard rock interspersed within each other

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23
Q

Concordant geology

A

Rock outcrops are parallel to the sea, creating straight coastline, though it can create coves

24
Q

How does vegetation influence the coast?

A
  • Biological weathering
  • Can create sand dunes via encouraging deposition, and then stabilise them
  • Can protect and preserve coastal landforms by buffering and reducing wave energy e.g. mangroves
25
Q

How does sea level influence the coast?

A
  • Flooding, a huge issue associated with rising sea level, especially considering many urban areas are situated on the coast
  • Saltwater incursion
  • Creation of landforms (different depending on whether sea levels are rising or falling - remember this is different in different parts of the world)
26
Q

How do people influence the coast?

A
  • Settlements
  • Fishing
  • Trade
  • Tourism
27
Q

What is the influence of wave refraction?

A

Waves approach parallel to coastline. As sea shallows, waves refract. This causes energy to concentrate on headlands (due to converging waves) more than bays (due to diverging waves). Despite this headlands remain sticking out due to their harder lithology

28
Q

How do cliffs and and wave cut platforms form?

A
  • Erosion is concentrated at the base of the cliff between the low tide and high tide mark in the wave attack zone.
  • This creates a wave cut notch.
  • The cliff above is undercut, is therefore unsupported and collapses due to gravity.
  • This creates a wave cut platform.
  • Over time, this repeats and the cliff retreats inland.
29
Q

How are caves formed?

A

Cliff surfaces are naturally made up of layers of rock called bedding planes and the joints between them are more susceptible to erosion. Joints are eroded and quickly expand, turning into larger cracks or fractures. Continued erosion through hydraulic action and abrasion will see these cracks expand

30
Q

How are arches formed?

A

When two caves back into one another, across a headland

31
Q

How are stacks formed?

A

Weathering processing, particularly freeze-thaw, weaken the roof of the arch until it eventually collapses leaving behind an isolated column

32
Q

How are stumps formed?

A

A stack continues to be impacted by weathering and erosion, until it can no longer be seen at high tide

33
Q

How are beaches formed?

A

Often form in bays, where the coast is sheltered from high-energy, erosional waves or where longshore drift provides a large supply of material

34
Q

Beaches

A

Areas where there is an accumulation of sand and shingle caused by deposition

35
Q

Spits

A

Long narrow beaches of sand or shingle, attached to the land at one end

36
Q

Bars

A

Long, narrow beaches of sand or shingle across bays or estuaries

37
Q

How are spits formed?

A
  1. Sudden change in coastline shape/direction
  2. Longshore drift has momentum and so continues to transport and deposit material at sea, following its original direction
  3. Over time sediment builds up creating a sandy ridge outcrop
38
Q

How are tombolos formed?

A

When a spit connects the mainland coast to an island or wave refraction around an island cause sediment to build up

39
Q

What is the distribution of coral reefs?

A

Between 30oN and S of the equator between the tropics

40
Q

Limiting factors of coral reef formation

A
  • Temperatures of 23-25o
  • <25m deep water as sunlight needed
  • Salinity
  • Clean water - too much sediment obscures sunlight and clogs feeding structures
  • Moderate wave action
41
Q

Features of coral reefs

A
  • Cover 1% of the ocean floor but have 25% of marine biodiversity contained within
  • Composed of coral polyps that have a symbiotic relationship with algae
42
Q

Biotic characteristics of the Great Barrier Reef

A

Coral, algae, fish, sharks, turtles, plankton, etc

43
Q

Abiotic characteristics of the Great Barrier Reef

A
  • Temperature
  • Water flow
  • Salinity level
  • pH of seawater
  • Light level
  • Nutrition availability
44
Q

Threats to coral reefs

A
  • Tourism, accidental trampling, carrying capacity could be exceeded
  • Industrialisation, water pollution, air pollution => rising temperatures => rising ocean temperatures => coral bleaching
  • Agriculture and deforestation, increased runoff => increased siltation, fertiliser runoff => eutrophication => decline in water quality
45
Q

Distribution of mangroves

A
  • 32oN and S of the equator
  • Sheltered intertidal areas that receive high annual rainfall
46
Q

Limiting factors of mangrove formation

A
  • Average temperature in coldest months above 20oC
  • Fine-grained substrate or sediment
  • The shores must be free of strong wave action and tidal current
  • Salt water
47
Q

Features of mangroves

A
  • Trap silt to create new land
  • Provides timber for building materials
  • Provides protection from storms, storm surges and tsunamis
48
Q

Threats to mangrove

A
  • Timber for fuel and building material
  • Aquaculture
  • Land reclamation for tourist hotels and other amenities
  • Diversion of fresh water
  • Farming requires application of herbicides to prepare for cultivation
49
Q

Distribution of sand dunes

A

Form worldwide at the interface between sea and land

50
Q

Limiting factors of sand dune development

A
  • Wide beach
  • Lots of sand
  • Obstacle e.g. marram grass
  • Onshore prevailing wind
51
Q

Features of sand dunes

A
  • Plant succession on dunes
  • Embryo dunes, foredunes, yellow dunes, grey dunes progression
  • Mature dunes contain more humus and have a higher pH
52
Q

Threats to sand dunes

A

Recreation e.g. trail biking, horse riding and golf courses

53
Q

Distribution of salt marshes

A
  • The intertidal zone
  • Sheltered areas e.g. bays, coves and behind spits
54
Q

Features of salt marshes

A
  • Either adapted to salt water or brackish water
  • Mudflats are colonised by vegetation over time, stable carr woodlands are permanently waterlogged at the back of the marsh
55
Q

Threats to salt marshes

A
  • Reclamation to create farmland and sites for industrial and port development
  • Industrial pollution, agricultural pollution
  • More storms, higher water levels

Geography (3 decks)

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