Coasts: coastal erosion and sea level change EQ3

Question 1

Give an example of when there is lower sea levels?

Answer 1

During an ice age - more liquid has turned into ice

Question 2

Give an example of when there is higher sea levels?

Answer 2

When the Earth’s climate is warmer - ice melts & water returns to seas and oceans

Question 3

Sea levels can change as a result of what?

Answer 3

Isostatic & Eustatic changes

Question 4

What is meant by Eustatic changes?

Answer 4

Rise of fall in water level caused by a change in the volume of water

Question 5

What is meant by Isostatic changes?

Answer 5

A local rise of fall in land level

Question 6

What type of change is a Eustatic change?

Answer 6

A global change - affecting all the world’s connected seas and oceans

Question 7

What type of change is an Isostatic change?

Answer 7

A local change

Question 8

How does changing amounts of ice cause Eustatic change? (give a real life example)

Answer 8

• End of the last ice age 10,000 years ago
• global sea level rose rapidly due to melting ice
• creating well-known waterways like the English Channel

Sea levels may also decrease when ice forms= locking water away in the ice sheets & glaciers

Question 9

How does Thermal expansion cause Eustatic change?

Answer 9

When water warms= warmer fluids expand & take up a greater volume

Question 10

How does Tectonics cause Eustatic change?

Answer 10

Magma rising to the surface lifts the crust= causing volume + shape of ocean basin to change= reduces the capacity of the oceans= causing sea levels to rise

Question 11

How does Post-glacial adjustment cause Isostatic change? (give a real life example)

Answer 11

• During a period of glaciation, extremely heavy icy sheets weigh land down
• When glacial period ends the ice melts & the land will rebound to a higher level= lowering the sea level

E.g. During last ice age
Most of Northern Britain covered in ice & Southern edge stayed ice free
- Area under ice pushed down in Earth’s mantle due to added weight
- causing local sea levels to rise in some places
As the ice melted with warming
- Weight was lifted off Northern Britain
- allowed land to slowly rebound upwards
- causing sea level to fall relative to the land rising
Sea levels now falling in Northern Scotland & rising in Southern Britain (where population density is highest)

Question 12

How does Subsidence cause Isostatic change?

Answer 12

Caused by lowering of water table or increased deposition weighing down the sediment

Question 13

How does Accretion cause Isostatic change?

Answer 13

Within the sediment cell, there are areas of net deposition causing land to build up

Question 14

How do Tectonics cause Isostatic change?

Answer 14

• The folding of the sedimentary rock
• Lava and ash from volcanoes increase the height of the land relative to the sea level

As tectonic plates collide= some areas of land are pushed up/others may sink

Volcanic island may form to create new coastlines= island arcs or hot spot locations e.g. Hawaii & Caribbean Islands

Question 15

What are the two types of coastline?

Answer 15

Emergent & Submergent

Question 16

Emergent coastlines:
- what are they?
- where are they commonly a result of?
- what 2 landforms are types of Emergent coastlines?
- what part of England can these commonly be found in?

Answer 16

• Parts of the littoral zone where a fall in sea level expose land once part of the seabed
• Isostatic rebound
• Raised beaches & Fossil cliff
• Northern parts such as in Scotland

Question 17

Emergent coastline landforms: Raised beach
- what are they?
- what are they like?
- what may they consist of?
- what do they experience?

Answer 17

• A former beach now above the high tideline
• flat and covered by sand/pebbles
• several different levels, indicating different stages of uplift
• succession

Question 18

Emergent coastline landforms: Fossil cliffs
- what are they?
- what erosion features can be seen here?

Answer 18

• Near-vertical slopes formed by marine processes found at the back of a raised beach
• Wave-cut notches, caves, and arches

Question 19

What do the Isle of Arran (an island in Scotland) have?

Answer 19

• Raised beaches 5m above current sea level
• Has 3 levels of raised beaches produced at different stages of post-glacial adjustment

Question 20

Submergent coastlines:
- what are they?
- where are they commonly a result of?
- happens when what?
- what 3 landforms are types of Submergent coastlines?
- Give an example of an area that has Submergent coastlines?

Answer 20

• Landforms that exist because of a rise in sea level
• Sea-level rise or Isostatic sinking
• coastlines are flooded
• A ria, A Fjord & A dalmation coast
• Norfolk coast

Question 21

Submergent coastline landforms: A ria
- what is it?
- how was it formed?
- so what type of coastline to they have?
- where are these commonly found in the UK?

Answer 21

• A flooded river valley
  During an ice age:
  some land areas were not covered with ice but had frozen ground= so rivers carved valley with steeper sides than normal
  After ice age:
  seal levels rose and drowned the mouths of these valleys
• An Estuarine coastline
• South-western England, e.g. Plymouth Sound

Question 22

Submergent coastline landforms: A Fjord
- what is it?
- how was it formed?
- what kind of profile do they have?

Answer 22

• A flooded glacial valley
  During ice age:
  glaciers eroded U-shaped valleys
  After ice age:
  after ice melted, sea level rose again and flooded into the valley over a shallow threshold= creating a very deep water inlet with steep sides
• steep profiles

Question 23

Submergent coastline landforms: Dalmatian coast
- what is it?
- what do they feature?
- what is one good example of where this can be seen?

Answer 23

• A submergent landform
• feature several linked parallel flooded valleys, with long islands between them
• In the eastern-shore of Croatia

Question 24

When the Earth is at its warmest what will have happened and cause?

Answer 24

It would have melted and the oceans will absorb heat and expand (thermal expansion)= these processes combine to raise sea levels

Question 25

When the Earth is at its coldest what will have happened and cause?

Answer 25

Ice will have grown to a maximum and the oceans will have cooled= sea level will be mush lower

Question 26

What is said to have stabilised around 3000 years ago?

Answer 26

Current levels of sea level

Question 27

What will increase as the world warms?

Answer 27

Eustatic sea level change & thermal expansion in ocean basins

Question 28

What % of the world's cities are coastal?

Answer 28

75%

Question 29

More than ... people live on high-risk coasts

Answer 29

1 Billion

Question 30

How have humans enhanced global warming since the 19th century? - this has been done through what?

Answer 30

The release of greenhouse gases into the atmosphere

Question 31

The melting of what & where could increase WATER OCEAN VOLUME?

Answer 31

Mountain glaciers in the Alps, Himalayas & other mountain ranges

Question 32

The melting of what & where could increase GLOBAL SEA LEVEL?

Answer 32

Major Ice sheets in Greenland and Antarctica

Question 33

Who is the IPCC & what did they estimate? - who does this create vulnerability for? - what could rising sea levels also do?

Answer 33

Intergovernmental Panel on Climate Change - estimated that sea levels by 2100 will be between 0.26-0.77m higher than they are now - people living in coastal cities and settlements - salinise aquifers in low-lying regions & increase coastal erosion

Question 34

Rapid coastal recession is caused by what factors but can be influenced by what other actions?

Answer 34

Caused by Physical factors & can be influenced by human actions

Question 35

What physical factors cause coastal recession? explain how

Answer 35

Geological Factors: - lithology= soft rock type, porous rocks - geological structure= well jointed rocks, rocks with seaward dipping beds, heavily faulted rocks Marine factors: - long wave fetch= promoting large destructive waves - strong LSD= quickly removes collapsed sediment allowing erosion to restart

Question 36

The most rapid rates of coastal recession is caused by: (5 things) The slowest rates of coastal recession is caused by: (4 things)

Answer 36

1. weakly consolidated rocks 2. large destructive waves 3. submergence of the coastline 4. large-scale mass movement 5. constant weathering processes 1. resistant rocks 2. smaller constructive waves 3. little mass movement 4. occasional or slow weathering processes

Question 37

Human actions: Explain how coastal defences can influence the rate of coastal retreat? (create a flow diagram)

Answer 37

Coastal defences built at one location= stop or limit the supply of sediment to a cell= another place down drift may not receive sediment for beach-building= beach gets narrower & less able to absorb wave energy= waves hit backshore more more force

Question 38

Human actions: Explain how offshore dredging can influence the rate of coastal retreat? (create a flow diagram) - give a real life example of where this is a problem

Answer 38

Offshore dredging removes sand and gravel for construction purposes= to deepen entrances to ports or to supply sediments for beach nourishment= deeper water allows waves to maintain their circular motion and energy closer inshore= have a more destructive impact on the coast - Dredging off the North Norfolk coast has been blamed for increased erosion rates & the supply of sediments to beaches has been altered

Question 39

Subaerial processes: How does Weathering accelerate recession rates? (create a flow diagram)

Answer 39

Weathering weakens the rocks at the coast= rainwater creates rills and gullies in unconsolidated material or at weak points in harder rock= allows erosion rates to increase

Question 40

Subaerial processes: How does Mass movement accelerate recession rates? (create a flow diagram)

Answer 40

Mass movement moves sediment to the base of cliffs= where wave action + LSD can carry material away= exposing the base of cliffs= resulting in cliffs retreating further

Question 41

Give a real life example of a place where Mass movement is more strongly linked than wave action to seasonal climate changes.

Answer 41

Overstrand in North Norfolk Has a full range of hard engineering coastal defences that protect cliff base from marine erosion BUT Cliff still retreats as a result of rain entering the rock layers= increasing pore pressure= causing slumping= leaving clear scars on cliff face + lobes of clay across the promenade

Question 42

Other factors: How does wind direction/Fetch affect rates of recession? - what does it determine? - what's the impact of this? - How does the fetch link to this? - what's its impact?

Answer 42

It determines wave direction - dominant wind produces largest waves= experience maximum erosion The Fetch: the distance from a coast across the ocean or sea to another coast - longer the fetch= larger more powerful the wave will be - so coasts with long fetches= likely to retreat faster

Question 43

Other factors: How do tides affect rates of recession? - what are the 2 different types of tide? - which one has the strongest gravitational pull and why? - which one has the weakest gravitational pull and why? - what do tides determine?

Answer 43

- High and Low tide - Extreme High tides (spring tides)= Sun & Moon are aligned so their total gravitational pull is the strongest - Lowest high tides (neap tides)= Sun & Moon are at right angles to each other so total gravitational pull is at its weakest - determine where waves will reach the shore e.g. high tide= waves more likely to reach the backshore & erode land faster high tide + destructive storm waves= erosion will be at maximum

Question 44

Other factors: How do weather systems affect rates of recession? - what is there in the UK? - what do these different pressures bring? - what has global warming done to this? - what does this mean for the UK?

Answer 44

- A seasonal weather pattern based on a sequence of high-pressure areas and low-pressure areas - High pressure bring calmer conditions= smaller waves - Low pressure brings larger waves especially during winter - added more heat to atmosphere= intensified the low-pressure systems - During storm events= experiences even stronger winds + larger waves

Question 45

Why are rates of recession likely to be greater in the winter months?

Answer 45

Storm events that cause destructive waves= more common in water months

Question 46

Why are flood risks increasing in coastal zones?

Answer 46

They are experiencing Isostatic sinking

Question 47

What happens during anticyclones (high pressure)?

Answer 47

gentle winds & low waves= rates of recession is lower

Question 48

What happens during depressions (low-pressure)?

Answer 48

winds much stronger & high waves= rates of recession is greater