ENQ3: How do Coastal erosion and sea level change alter the physical characteristics of coastlines
and increase risks
2.7 Sea Level Change Influences coasts on different timescales
2B.7a Longer-term sea level changes result from a complex interplay 2B.7b Sea level change has produced emergent coastlines
of factors both eustatic (ice formation/melting, thermal changes) and (raised beaches with fossil cliffs) and submergent coastlines
isostatic (post-glacial adjustment, subsidence, accretion) and (rias, fjords and Dalmatian).
tectonics.
Emergent coastlines:
Long-term sea-level change
Eustatic GLOBAL SEA LEVEL CHANGE
change Ice formation/melting:
- Glacial periods (90K years colder phases) -> formation
of ice sheets. Decreases volume of water in oceans = sea
level fall.
o Most recent = Devensian Ice Age where Sea levels
were 120m lower than they are today.
- Inter – glacial (10k year warmer phases) shrink ice
sheets, water melts transferring from land back to ocean
= sea levels rise. Definition/ - Coastlines where land has risen relative to the sea.
Thermal changes: causes - Post glacial adjustment -> isostatic land rebounds
- As oceans water warms, it expands. causing fall in sea level.
- Leads to thermal expansion. - Fall in global sea level -> eustatic fall during
- Small change in temp = significant difference. glacial periods.
- Accelerated by human activity. Features Raised beaches:
Isostatic LOCALIZED SEA LEVEL CHANGE - Beaches now above high tide level/current sea
change: Caused by change in the height of land relative to sea level.
level - Flat surfaced covered with sand, pebbles and wave
- Post – glacial adjustment (isostatic rebound): cut notches.
o Glacial periods = weight of ice depresses crust. - Usually vegetated by plant succession.
o Adjacent areas are uplifted + rebound = sea saw - Isle of Arran Scotland = raised beach 5M above
effect. sea level.
o Once ice melts, previously ice – covered crust Fossil Cliff:
slowly rebound upwards whilst other areas will - Former cliff lines now found inland.
subside. - Steep slope at back of a raised beach.
- EXAMPLE: - Now above high high tide due to fall in sea level.
o End of Devensian ice age 12k years ago, UK - Wave cut notches, caves, arches showing
covered in ice. previously marine erosion.
o North Britain experienced isostatic sea level fal as - No longer actively eroded by sea
land was uplifted by 1.5mm per annum.
o South Britain experienced isostatic sea level rise as Submergent coastlines
land lowered by 1mm per year. Defintion/ - Coastlines flooded due to rising sea levels
- Subsidence: land sinks: causes normally inter – glacial periods.
o CC leads to increase EV rates + human - Eustatic sea level rise -> melting of ice.
abstraction of water. - Tectonic subsidence.
Lowers water table. - Isostatic sea level rise -> land subsidesf
Pore water pressure that supports Features Rias:
sediment is lost. - Ri ver valleys in lower course flooded.
Sediment settles causing land to subside. - Partially submerged by rising sea levels.
o Increase sediment deposition: - Common in periglacial areas where rivers
River deltas – Amazon, Nile etc. erode v – shaped valleys into frozen
Deposition exceeds threshold. landscapes.
Leads to crust sag. - Deep, narrow, branching.
Land subsidence. - Can be econ impprtant = sheltered ports.
o Isostatic rebound causes adjacent areas to subside. - Kingsbury estuary in deveon = 6M long ria.
o Heavy infrastructure – increases weight.
- Accretion:
o Sink regions in sediment cell experience ne
deposition.
o Delta regions.
o Raises land locally and can counter – act sea level
rise in some areas.
Tectonic Destructive plate margin:
s - - Folding of rocks due to compressive forces.
isostatic - Land uplifted.
- Isostatic Sea level fall for anitclines and cynclines.
- Alpine folding at Eurasian – African destructive plate Fjords:
boundary produced an isostatic fall of 60cm in Bakar – - Glacial valleys flooded due to eustatic change.
Vindol area in Croatia - Deeper and steeper sided than rias.
- Formed when glaciers carve deep valleys that
flood when ice melts.
Lava/ash: - Songeford in Norway = 205km long Fjord.
- Volcanic activity.
- Builds up land.
- Causes isostatic sea level fall
- Hawaiian Hotspot islands.
Sea flood spreading:
- Carries volcanic islands away from uplifted crust at mid
ocean ridge.
- Colder more denser plate subside
- Causes isostatic rise in sea level
- Kirabiti, Tonga, Fiji
Dalmation Coastline:
Submergence:
- Coastlinee of long, narrow islands and ridges
- After earthquake, land may subside.
running paralle to coast but separated by
- Cause isostatic rise in sea level.
coast by narrow sea channels.
- 2004 Boxing Dam Tsunami in Indian Ocean extension of
- Produced from sea level rise.
, crustal plate caused isostatic fall in land on island of - Folded rock structures partially submerged
Sumatra by 20cm in Banda Aceh region. creating synclines and anticlines.
- Dalmation coastline in Croatia has 1200
parallel islands.
Tectonic Constructive plate boundary (plates moving apart):
s– - As plates move apart, magma rises.
eustatic - Uplift of ocean floor.
- If crust uplifts, ocean basin becomes shallower.
- Reduces capacity to hold water
- Extra water = displaced.
- Causes eustatic sea level rise.
- Indian ocean = parts of ocean crust uplifted causing
0.1mm global sea level rise.
2B.7c Contemporary sea level change from global warming or Key areas at risk:
tectonic activity is a risk to some coastlines.
Low lying - Maldives, Kirabiti, Tuvalu.
Causes: areas - Risk of becoming uninhabitable.
Global warming Thermal expansion: Delta - Ganges Delta – Bangaldesh
- Increase in temp -> warmer oceans -> water regions - Nile Dela. Egypt
expansion -> sea level rise. - Prone to flooding and land loss
- IPCC – attributes 40% of sea level rise 1990 – Major - New York, Miamia, Jakarta.
2010 due to thermal expansion. coastal
Melting of ice sheets and glaciers cities
- Melting of glaciers -> global eustatic sea level
rise.
- NOT melting of sea ice = no effect on sea lvel
as ice was already displacing equivalent Coastal risks from contemporary sea level rise:
volume of water. - Coastal flooding -> low lying eras, permaemnt flooding.
- IPCC attributes 50% of sea level rise between - Storm sruges -> higher sea levels, more powerful storm surges.
1990 – 2010 due to ice sheets melting. - Coastal erosion -> rising sea levels allow waves to reach further
-global average rise of 3-4mm per year. inland
Tectonic activity Causes 10% of sea level rise. - Saltwater intrusion -> sea water infiltraes freshwater supplies.
Earthquakes and volcanic activity: - Loss of ecossytems -> coastal wetlands, salt marshes, mangroves
- Sudden uplift of land or subsidence. drown.
Tsunamis:
- Cause temporary but devastating changes to
coastal profiles
CASE STUDY : 2004 Indian Ocean earthquake
- 9-9.3 on Richter scale.
- Indonesian Islanf of Sumatra = worse hit.
- City of Banda Aceh hit by 15m high waves.
- Flooded within 15mins of initial earthquake.
- Made land sink in Banda Aceh by 60cm.
- How did it cause sea level rise:
o 1600km of fault line shifting – Indian
plate sliding under the Burma plate via
subduction.
o Seabed rose several metres.
o Seabed uplift displaced 30km3 of water,
triggering tsunami.
o Some areas permanently submerged.
o Seabed rose making coean shallower and
Indian ocean total capcity decreased.
o CAUSED global sea level rise by 0.1mm.
Future - IPCC predicts rise of 18-59Cm by 2100.
predictions for - Wide variation in prediction b.c:
sea level rise o Uncertainities in relationship between
GHG increase + cimate warming.
o Uncertianites over relationship between
warming and rate of ice melting.
o Uncertainities voer population +
economic growth impacting GHG
emissions
o Uncertainity about commitment to
reducing GHG emissions.
Key words Questions
Describe and explain the different types of sea level change and
apply it to examples.
Understand that climate change plays an important role in
determining coastlines of the past, present and future.
Assess the different methods of classifying coastlines.
and increase risks
2.7 Sea Level Change Influences coasts on different timescales
2B.7a Longer-term sea level changes result from a complex interplay 2B.7b Sea level change has produced emergent coastlines
of factors both eustatic (ice formation/melting, thermal changes) and (raised beaches with fossil cliffs) and submergent coastlines
isostatic (post-glacial adjustment, subsidence, accretion) and (rias, fjords and Dalmatian).
tectonics.
Emergent coastlines:
Long-term sea-level change
Eustatic GLOBAL SEA LEVEL CHANGE
change Ice formation/melting:
- Glacial periods (90K years colder phases) -> formation
of ice sheets. Decreases volume of water in oceans = sea
level fall.
o Most recent = Devensian Ice Age where Sea levels
were 120m lower than they are today.
- Inter – glacial (10k year warmer phases) shrink ice
sheets, water melts transferring from land back to ocean
= sea levels rise. Definition/ - Coastlines where land has risen relative to the sea.
Thermal changes: causes - Post glacial adjustment -> isostatic land rebounds
- As oceans water warms, it expands. causing fall in sea level.
- Leads to thermal expansion. - Fall in global sea level -> eustatic fall during
- Small change in temp = significant difference. glacial periods.
- Accelerated by human activity. Features Raised beaches:
Isostatic LOCALIZED SEA LEVEL CHANGE - Beaches now above high tide level/current sea
change: Caused by change in the height of land relative to sea level.
level - Flat surfaced covered with sand, pebbles and wave
- Post – glacial adjustment (isostatic rebound): cut notches.
o Glacial periods = weight of ice depresses crust. - Usually vegetated by plant succession.
o Adjacent areas are uplifted + rebound = sea saw - Isle of Arran Scotland = raised beach 5M above
effect. sea level.
o Once ice melts, previously ice – covered crust Fossil Cliff:
slowly rebound upwards whilst other areas will - Former cliff lines now found inland.
subside. - Steep slope at back of a raised beach.
- EXAMPLE: - Now above high high tide due to fall in sea level.
o End of Devensian ice age 12k years ago, UK - Wave cut notches, caves, arches showing
covered in ice. previously marine erosion.
o North Britain experienced isostatic sea level fal as - No longer actively eroded by sea
land was uplifted by 1.5mm per annum.
o South Britain experienced isostatic sea level rise as Submergent coastlines
land lowered by 1mm per year. Defintion/ - Coastlines flooded due to rising sea levels
- Subsidence: land sinks: causes normally inter – glacial periods.
o CC leads to increase EV rates + human - Eustatic sea level rise -> melting of ice.
abstraction of water. - Tectonic subsidence.
Lowers water table. - Isostatic sea level rise -> land subsidesf
Pore water pressure that supports Features Rias:
sediment is lost. - Ri ver valleys in lower course flooded.
Sediment settles causing land to subside. - Partially submerged by rising sea levels.
o Increase sediment deposition: - Common in periglacial areas where rivers
River deltas – Amazon, Nile etc. erode v – shaped valleys into frozen
Deposition exceeds threshold. landscapes.
Leads to crust sag. - Deep, narrow, branching.
Land subsidence. - Can be econ impprtant = sheltered ports.
o Isostatic rebound causes adjacent areas to subside. - Kingsbury estuary in deveon = 6M long ria.
o Heavy infrastructure – increases weight.
- Accretion:
o Sink regions in sediment cell experience ne
deposition.
o Delta regions.
o Raises land locally and can counter – act sea level
rise in some areas.
Tectonic Destructive plate margin:
s - - Folding of rocks due to compressive forces.
isostatic - Land uplifted.
- Isostatic Sea level fall for anitclines and cynclines.
- Alpine folding at Eurasian – African destructive plate Fjords:
boundary produced an isostatic fall of 60cm in Bakar – - Glacial valleys flooded due to eustatic change.
Vindol area in Croatia - Deeper and steeper sided than rias.
- Formed when glaciers carve deep valleys that
flood when ice melts.
Lava/ash: - Songeford in Norway = 205km long Fjord.
- Volcanic activity.
- Builds up land.
- Causes isostatic sea level fall
- Hawaiian Hotspot islands.
Sea flood spreading:
- Carries volcanic islands away from uplifted crust at mid
ocean ridge.
- Colder more denser plate subside
- Causes isostatic rise in sea level
- Kirabiti, Tonga, Fiji
Dalmation Coastline:
Submergence:
- Coastlinee of long, narrow islands and ridges
- After earthquake, land may subside.
running paralle to coast but separated by
- Cause isostatic rise in sea level.
coast by narrow sea channels.
- 2004 Boxing Dam Tsunami in Indian Ocean extension of
- Produced from sea level rise.
, crustal plate caused isostatic fall in land on island of - Folded rock structures partially submerged
Sumatra by 20cm in Banda Aceh region. creating synclines and anticlines.
- Dalmation coastline in Croatia has 1200
parallel islands.
Tectonic Constructive plate boundary (plates moving apart):
s– - As plates move apart, magma rises.
eustatic - Uplift of ocean floor.
- If crust uplifts, ocean basin becomes shallower.
- Reduces capacity to hold water
- Extra water = displaced.
- Causes eustatic sea level rise.
- Indian ocean = parts of ocean crust uplifted causing
0.1mm global sea level rise.
2B.7c Contemporary sea level change from global warming or Key areas at risk:
tectonic activity is a risk to some coastlines.
Low lying - Maldives, Kirabiti, Tuvalu.
Causes: areas - Risk of becoming uninhabitable.
Global warming Thermal expansion: Delta - Ganges Delta – Bangaldesh
- Increase in temp -> warmer oceans -> water regions - Nile Dela. Egypt
expansion -> sea level rise. - Prone to flooding and land loss
- IPCC – attributes 40% of sea level rise 1990 – Major - New York, Miamia, Jakarta.
2010 due to thermal expansion. coastal
Melting of ice sheets and glaciers cities
- Melting of glaciers -> global eustatic sea level
rise.
- NOT melting of sea ice = no effect on sea lvel
as ice was already displacing equivalent Coastal risks from contemporary sea level rise:
volume of water. - Coastal flooding -> low lying eras, permaemnt flooding.
- IPCC attributes 50% of sea level rise between - Storm sruges -> higher sea levels, more powerful storm surges.
1990 – 2010 due to ice sheets melting. - Coastal erosion -> rising sea levels allow waves to reach further
-global average rise of 3-4mm per year. inland
Tectonic activity Causes 10% of sea level rise. - Saltwater intrusion -> sea water infiltraes freshwater supplies.
Earthquakes and volcanic activity: - Loss of ecossytems -> coastal wetlands, salt marshes, mangroves
- Sudden uplift of land or subsidence. drown.
Tsunamis:
- Cause temporary but devastating changes to
coastal profiles
CASE STUDY : 2004 Indian Ocean earthquake
- 9-9.3 on Richter scale.
- Indonesian Islanf of Sumatra = worse hit.
- City of Banda Aceh hit by 15m high waves.
- Flooded within 15mins of initial earthquake.
- Made land sink in Banda Aceh by 60cm.
- How did it cause sea level rise:
o 1600km of fault line shifting – Indian
plate sliding under the Burma plate via
subduction.
o Seabed rose several metres.
o Seabed uplift displaced 30km3 of water,
triggering tsunami.
o Some areas permanently submerged.
o Seabed rose making coean shallower and
Indian ocean total capcity decreased.
o CAUSED global sea level rise by 0.1mm.
Future - IPCC predicts rise of 18-59Cm by 2100.
predictions for - Wide variation in prediction b.c:
sea level rise o Uncertainities in relationship between
GHG increase + cimate warming.
o Uncertianites over relationship between
warming and rate of ice melting.
o Uncertainities voer population +
economic growth impacting GHG
emissions
o Uncertainity about commitment to
reducing GHG emissions.
Key words Questions
Describe and explain the different types of sea level change and
apply it to examples.
Understand that climate change plays an important role in
determining coastlines of the past, present and future.
Assess the different methods of classifying coastlines.
