Lesson 12- How are coastal landforms influenced by isostatic and eustatic sea level rise?

Question 1

What would happen if all the ice melted on earth?

Answer 1

• 3% of all water is fresh-70% of this is frozen
• 95% of ice is land based
• 10% of global population would be displaced up to 10m of sea level
• White ice melts which has a high albedo effect but then theres more blue/green which has a low albedo effect and therefore holds heat more and warms up the planet

Question 2

What acctually is sea level change?

Answer 2

• Change in short-term period such as day-to-day or minute to minute due to factors such as high tide and low tide, wind strength and changes in direction or changes in atmospheric pressure

Question 3

How has sea level changed?

Answer 3

• IPCE predicts sea level rise between 0.3-1m by 2100
• Since records began they have always been rising from 120m below what they are now
• Since 1880 and the industrial revelution, sea levels have increased by around 235mm which may not seem a lot but is significant enough to overwhelm some sea defences with storm surges as well

Question 4

What are the possible causes of the sea level change?

Answer 4

• During cold glacial periods global sea levels are much lower which affects the location of coastal landforms and processes
• Current changes in the global carbon cycle affect physical processes at the coast but also human ones as coastal regions are eroding faster and at greater risk of coastal flooding

Question 5

Eustatic change

Answer 5

• This is global. In cold glacial periods, precipitation falls as snow (rather than rain) and forms huge ice sheets that store water that is usually held in the oceans
  -As a result sea levels fall. As temperatures rise at the end of glacial periods, the ice sheets begin to melt and expand as water warms due to thermal expansion.
  -magma rising to surface lifts the crust and reduces capacity of the ocean causing higher sea level

Question 6

Isostatic change

Answer 6

• This occurs locally. During glacial periods, the enormous weight of the ice sheets makes the land sink – isostatic subsidence. As ice begins to melt at the end of a glacial period, the reduced weight of the ice causes the land to readjust and rise – isostatic recovery.
  -folding of sedimentary rock can increase the height of the land compared to the sea

Question 7

What impacts does changing sea level acctually have?

Answer 7

• Current sea levels stabalised around 3,000 years ago
• More than 1 billion people live on high risk coasts
  -75% of cities are coastal

Question 8

What are the different types of coastline created by sea level change?

Answer 8

• Emergent have features associating with falling relative sea levels. E.g relict cliffs
  -where land has risen or sea levels drop
• Submergent have features that suggest relative sea levels like Fjords
  -where sea levels have risen at the end of the ice age

Question 9

Emergent landforms

Answer 9

• Raised beaches-beach above sea level unreachable at high tide-sometimes called marine terrice
  Relict cliffs-Where land has risen from the sea in the past as a result of isostatic processes
  -steep slope at back of beach

Question 10

Submergent landforms

Answer 10

• Rias-A drowned river
  -rising sea levels relative to the land rebranding flood river valleys leaving only high land visable
• Fjords-A drowned glacial valley- U shaped valleys left by glaciers are submerged
• Dalmatian Coasts-Formed in areas where valleys lie paralell to each other
  -when valleys get flooded, the tops remain above the surface