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Geography - B - Coastal Landscapes > Block 8 (Variations In Coastal Processes, Coastal Landforms + Landscapes Over Different Time Scales) > Flashcards

Block 8 (Variations In Coastal Processes, Coastal Landforms + Landscapes Over Different Time Scales) Flashcards

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1
Q

What are the three time scales we look at in relation to coasts?

A
  • Seconds
  • Seasons
  • Millennia
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2
Q

What are the coastal changes over seconds?

A
  • High energy storm events

- Rapid mass movement

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3
Q

What causes high energy storm events?

A

Increased wave energy

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4
Q

What processes are increased during high energy storm events?

A
  • Erosion (more destructive waves)

- Transportation (more energy to carry larger/more material)

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5
Q

How do high energy storm events cause coastal change?

A
  • Change in beach profile (sediment removal, storm beach formed)
  • Destruction or breaching of sand dunes (increased erosion)
  • Coastal flooding (particularly if there is a storm surge)
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6
Q

What conditions facilitate a storm surge to form?

A
  • Storm with strong onshore winds
  • High (spring) tide
  • Low pressure (allows waves to rise)
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7
Q

When pressure decreases by 1mb, how much does wave height increase by?

A

1cm

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8
Q

What causes mass movement?

A

Material become unstable, and is moved downslope under influence of gravity

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9
Q

Give an example of change over seconds due to high energy storm events

A

North Sea Storm Surge of 1953

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10
Q

Give an example of change over seconds due to rapid mass movements

A

Hive Beach, Dorset - 2012

  • 50 m high cliffs made of soft sandstone
  • Heavy rain made cliff saturated, heavy - unstable
  • Landslide
  • 400 tonnes rock fell
  • 1 fatality
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11
Q

What changes to coast do rapid mass movements cause?

A
  • Change in cliff face profiles
  • Retreating cliff line
  • Potential damage to cliff top development
  • Change in beach profile (may have sediment on)
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12
Q

What are the changes over seasons we look at?

A

Seasonal changes to beach profile

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13
Q

What causes the seasonal change to beach profile?

A

Weather differences + how this influences wave type

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14
Q

What is typical summer weather + the waves this produces?

A

Anticyclonic weather

  • Dry, with few storms
  • Calm, with low wind speeds
  • Causes low energy waves that are predominantly constructive (spilling)
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15
Q

What is typical winter weather + the waves this produces?

A

Depressions

  • Wet, with more storms
  • High wind speeds
  • Causes high energy waves that are predominantly destructive (plunging)
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16
Q

What is the typical beach profile in summer?

A

Sandy, wide, dissipative beach

  • Sandy: Less energy, so only fine sand can be moved ashore
  • Wide
  • Dissipative: Shallow gradient, formed by constructive waves (spilling)
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17
Q

What is the typical beach profile in the Winter?

A

Rocky, narrow, reflective beach

  • Rocky: more energy, so large material can be moved ashore
  • Narrow
  • Reflective: steep gradient, formed by destructive waves (plunging)
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18
Q

Give an example of an area where beaches typically undergo seasonal change

A

California, USA

Sandy summer, rocky winter

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19
Q

Give an example of a freak seasonal change

A

Dooagh, Ireland

  • Rocky for 34 years
  • Freak tidal event in 2017
  • Became sandy for 2 months
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20
Q

What are the changes over millennia?

A
  • Eustatic sea level change

- Isostatic sea level change

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21
Q

What is the ‘absolute’ sea level?

A

Sea level based on volume of water, regardless of land position

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22
Q

What is eustatic change?

A

Global changes to the absolute sea level

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23
Q

What are the two main causes of eustatic change?

A
  • Glacio-eustatic change

- Thermal expansion

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24
Q

What is glacio-eustatic change?

A

Continental ice melts, releasing water into sea

Floating ice melting does not contribute - as vol ice lost = vol water gained

25
Q

What is thermal expansion?

A

As temp rises, water particles take up more volume

26
Q

What is the greatest cause of eustatic change to sea levels? Give figures to exemplify

A

Glacio-eustatic change

  • Est all Antarctica + Greenland’s ice melting would cause rise of 90m
  • Thermal expansion only makes difference of approx 10m
27
Q

What is isostatic change?

A

Regional changes to sea level caused by localised uplift/sinking land

28
Q

What are the three causes of isostatic change?

A
  • Isostatic rebound/readjustment
  • Glacio-isostasy
  • Hydro-isostasy
29
Q

What is isostatic rebound/readjustment?

A

Melting of ice removes weight from the crust in that area, causing that area to rise

  • Happens after glacio-isostasy
  • Sea level LOWERS relative to land
30
Q

What is glacio-isostasy?

A

Glaciated areas are depressed by the weight of the ice

- Sea level RISES relative to land

31
Q

What is hydro-isostasy?

A

Increased volume of water in ocean basins weighs down ocean floor, depressing it
- Sea level FALLS relative to land

32
Q

How much of the 90m eustatic rise is thought to be cancelled out in Antarctica + Greenland areas due to hydro-isostasy?

A

60m

33
Q

What impact does rising/falling sea levels have on the coastline?

A
  • Rising sea levels cause SUBMERGENT COASTLINES

- Falling sea levels cause EMERGENT COASTLINES

34
Q

What are emergent coastlines?

A

Coastlines building out, as a result of MARINE REGRESSION (relative fall of sea levels)

35
Q

What 3 scenarios can cause the formation of emergent coastlines?

A
  • Sea levels fall faster than land falls/stays same/rises
  • Sea levels stay same + land rises
  • Sea levels rise but land rises faster
36
Q

What are the emergent landforms?

A
  • Raised beaches

Often accompanied by: old landforms, relic/fossil cliffs, marine terrace

37
Q

What are raised beaches?

A

Beaches left stranded above the new sea level, no longer affected by waves

38
Q

What 3 features often accompany raised beaches?

A
  • Old landforms (e.g. old CASS sequence)
  • Relict/fossil cliffs (old, steep cliffs, now weathered but not eroded)
  • Marine terrace (old wave cut platform, often used for agriculture)
39
Q

Give an example of a raised beach

A

Raised beaches in Western Scotland

  • Beaches have been raised up to 30m above sea level
  • Isostatic rebound is happening at approx 2mm/yr there
  • Raised beach backed by relict cliffs can be seen at Gruinard Bay
40
Q

What is a submergent coastline?

A

Coastline drowned, as a result of MARINE TRANSGRESSION (relative rise in sea levels)

41
Q

What 3 scenarios cause formation of submergent coastlines?

A
  • Sea level falls + land falls faster
  • Sea level stays same + land falls
  • Sea level rises + land falls/stays same/rises slower
42
Q

What are the submergent landforms?

A
  • Rias
  • Fjords
  • Fjards
  • Dalmatian coasts
43
Q

What is a ria?

A

Flooded river channel

44
Q

What are the characteristics of a ria?

A
  • Form on discordant coastlines
  • V-shaped (with gentle sides)
  • Widest at sea, getting narrower inland
  • Maintain dendritic drainage system (tributaries)
45
Q

Give an example of a ria

A

Kingsbridge estuary, Devon

46
Q

What is a fjord?

A

Flooded glacial valley

47
Q

What are the characteristics of a fjord?

A
  • U-shaped (steep sides)
  • Narrow (get narrower moving inland) (never wider than they are long)
  • Deep (deepest in middle)
    Often accompanied by:
  • Hanging valleys + waterfalls
  • Skerries (small rocky islands at the shallow fjord entrance - threshold)
48
Q

Give an example of a fjord

A

Sognefjord, Norway

  • 204km long
  • 1308 km deep
49
Q

What is a fjard?

A

Flooded inlet (geo) rather than a whole valley

  • Very similar to fjords
50
Q

Give an example of a fjard

A

Hjortsholm, Denmark

51
Q

What is a Dalmatian coast?

A

Group of small islands parallel to the coast, formed by flooded valleys called ‘sounds’

52
Q

Where are Dalmatian coasts found?

A

On concordant coastlines, where valleys lie parallel to coast

53
Q

Give an example of a Dalmatian coast

A

Dalmatian Coast, Croatia

  • Originally folded into synclines + anticlines
  • After Ice Age, low synclines + low points on anticlines flooded, leaving ridges
54
Q

What eustatic + isostatic sea level changes occur during a glacial period?

A

Eustatic - Ice freezes, temps fall - eustatic absolute fall in sea levels

Isostatic - Ice weighs down land - localised relative sea level rise (glacio-isostasy)

55
Q

What eustatic + isostatic sea level changes occur during an interglacial period?

A

Eustatic - Ice melts, temps rise - eustatic absolute rise in sea levels

Isostatic - Weight of ice removed from land and seabed weighed down- localised relative fall in sea levels (isostatic rebound) (hydro-isostasy)

56
Q

What was the last Ice Age called + when did it end?

A

The Devensian, ended 10,000 yrs ago

57
Q

What period are we in now + what is happening?

A

The Holocene, interglacial period where temps + eustatic sea levels have risen, rate accelerated by humans

58
Q

What is the risk of the current eustatic sea level rise?

A

Over 600 million people live less than 10m above sea level
Could face…
- Settlement loss
- Coastal flooding
- Increased insurance/management costs
- Salt + fresh water mixing in underground stores, reducing potable water
- Environmental damage, e.g habitat loss

Geography - B - Coastal Landscapes (10 decks)

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