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Physical geography > Coasts 4 - Sea level changes > Flashcards

Coasts 4 - Sea level changes Flashcards

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1
Q

What scale are the affects of eustatic change on

A

Global

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1
Q

What is eustatic sea level change caused by?

A

A change in the volume of water in the sea or by a change in the shape of ocean basins (worldwide level change)

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2
Q

What causes these global affects?

A

Changes in climate and tectonic movement of crust

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3
Q

How does an increase in temperature change sea levels

A

Causes ice sheets to melt increasing sea level. Also causes water to expand increasing sea levels

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4
Q

How does a decrease in temperature change sea levels

A

Causes more precipitation to fall as snow, increasing the volume of water stored in glaciers and reduces the volume of sea decreasing sea levels

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5
Q

What does tectonic movements of crust do

A

After the shape and volume of ocean basins eg - sea floor spreads increases the volume of the basin and decreases sea level

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6
Q

What is isostatic sea level change caused by

A

Vertical movements of the land relative to the sea

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7
Q

What does downward and upward land cause

A

Downward - Sea level to rise locally
Upward - Sea level to fall locally

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8
Q

What are the 3 causes of isostatic sea level change

A

1) Tectonic processes - eg - 1 plate is forced beneath another at a plate margin
2) Subsidence of land due to shrinkage after abstraction of ground water like drainage or marshland
3) Uplift or depression of the earths crust due to accumulation or melting. If its slow it continues for 1000s of years after the retreating glacier has gone

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9
Q

Where and what does accumulation of sediment cause?

A

The mouths of major rivers causing depression

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10
Q

What does sea level vary with

A

The tidal cycle

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11
Q

What else causes the sea surface to rise temporarily

A

Onshore winds and low atmospheric pressure systems

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12
Q

Give 4 ways global sea level has changed

A

1) Last glacial period, water was ice sheets, so sea level was lower. At the last glacial maximum sea level was 130m lower than now
2) As temp increases, ice sheets ,melt and sea level rose rapidly. It reached its present level around 4000 years ago
3) Over the last 4000 years sea level has fluctuated above and below current level
4) Since 1930, sea levels have been rising

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13
Q

What is global warming?

A

Temperatures increasing rapidly over the last century

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14
Q

Whyat do scientists think is the cause of climate change

A

Human activity - deforestation and burning fossil fuels

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15
Q

What do these activities do

A

Increase the concentration of greenhouse gases in the atmosphere

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16
Q

What do greenhouse gases do

A

Absorb outgoing long-wave radiation, so less is lost in space. As their concentration increases more energy is trapped and the planet warms up

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17
Q

Why is an increase in temp likely to cause an increase in sea levels

A

Through melting of ice sheets and thermal and expansion of water in oceans

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18
Q

How is global sea levels currently rising

A

2mm a year

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19
Q

What will happen if greenhouse gas emissions remain high?

A

It’s predicted to increase 8 to 16mm a year by 2100

20
Q

Why are storms likely to9 become more frequent and intense

A

Changes in ocean circulation and wind pattens

21
Q

What would this do

A

Damage ecosystems and settlements

22
Q

What are 4 major impacts will sea level rise have on coastal areas

A

1) More frequent and severe flooding
2) Submergence of low-lying islands
3) Changes in coastline
4) Contamination if water sources and farmland

23
Q

How does more frequent and serve coastal flooding happen

A

Flooding of low lying areas has increased with sea level rise and it will increase more with further rises

24
Q

What is an example of more frequent and serve coastal flooding

A

From 1995 - 2004, Kings Point in New York flooded 80 times but from 2005 - 2014 it was nearly 160

25
Q

What is submergence of low-lying islands?

A

Lots of low-lying islands are at risk of disappearing

26
Q

Give an example of submergence of low - lying islands

A

If the sea levels rise by 0.5m from its current level most of the Maldives will be submerged

27
Q

How are coastlines changing

A

Islands are created and the area of land is decreased

28
Q

Give an example of changes in coastline

A

If sea levels rise by 0.3m from its current level, 8000km of land in Bangladesh will be lost

29
Q

How does contamination of water sources and farmland happen

A

Salt water enters freshwater near the coast and damages ecosystems and makes the water unsuitable

30
Q

How does this affect farmland?

A

Damages crops and makes land impossible to farm

31
Q

What does increased sea level rise and storminess cause?

A

Increased coastal erosion and puts ecosystems, homes and businesses at risk

32
Q

What happens when sea level falls relative to the coast

A

New coastline emerges from the sea creating different landforms

33
Q

What landforms does this create (3)

A
  • Raised Beaches
  • Cut platforms
  • Relicit Cliffs
34
Q

When are raised beaches formed

A

Fall in sea levels leave beaches above the high tide mark. Over time, beach sediment becomes vegetated and develops into soil

35
Q

How are wave-cut platforms formed

A

Sea level fall exposes wave-cut platforms, leaving them raised above their former level

36
Q

How are relicit cliffs formed

A

Cliffs above raised beaches aren’t eroded by the sea and slowly gets covered by vegetation

37
Q

What landforms are created when sea level rises relative to the coast (3)

A
  • Rias
  • Fjords
  • Dalmation coats
38
Q

When are rias formed?

A

When river valleys are partially submerged

39
Q

Describe a ria

A

They have gentle long and cross-profile, they’[re wide and deep at the mouth, becoming narrower and shallower the further inland they reach

40
Q

What are fjords

A

Drained glacial valleys

41
Q

Describe fjords

A

Relatively straight and narrow, with steep sides. They have a shallow mouth caused by a raised bit of ground formed by deposition of material by the glacier. They’re very deep further inland

42
Q

When is a Dalmatian coastline formed

A

In areas where valleys lie parallel to the coast, an increase in sea level forms this. Valleys are flooded, leaving islands parallel to the coastline

43
Q

How are landscapes formed

A

Individual landforms combine

44
Q

How are coastal landscapes dominated

A

By processes of erosion or deposition, but most are formed by both

45
Q

What 2 ways do coastal landscapes change over time

A
  • A change in 1 factor leads to a change in others, eg - a change in wave direction may increase deposition and change a landscape dominated by erosive landforms to a new one dominated by depositional landforms
  • Relicit landforms experience coastal processes, eg - a relict cliff maybe weathered vey salt and freeze-thaw
46
Q

What are coastal landscaped made up of

A

Mixture of active and elicit landforms reflecting different periods of change

47
Q

Where do these changes occur

A

On a range of spatial and temporal scales

Physical geography (16 decks)

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