Sea Level Change 3.1

Emergent coastlines features

• Landforms exists due to reduction in sea level

• Happens during isostatic recovery (land rebounds)

• They are raised beaches and fossil cliffs

Raised beaches (emergent landform)

• They’re beaches above high tide, flat and covered with sand.

• They experience succession

• E.g. many raised beaches in the Scottish islands of Islay

Fossil Cliff (emergent landform)

• steep slope at the back of a raised beach

• Wave-cut notches, caves, arches may be present

Sea level change

It happens as a result of Isostatic and Eustatic changes.

• Eustatic is when sea level rises and falls, happens globally

• isostatic change is local

Eustatic change

• Happens due to changes in amount of ice due to thermal expansion and tectonics.

• The changes are global

Eustatic change- changing amounts of ice

• At the end of last ice age (10,00yrs ago) global sea levels rose due to melting ice- this created the English Channel

• Sea levels may decrease when ice forms, locking water away in glaciers

Eustatic change- thermal expansion

Occurs as water warms, warmer fluids expand which take up a greater volume

Isostatic change

• it’s the change in local land level

• Occurs when the weight of earths crust changes

• Happens due to post-glacial adjustment, accretion, subsidence,

Post-glacial adjustment - isostatic change

• during glacial period, heavy ice sheets weighed land down

• After glacial period, ice melts causing land to rebound back to higher level, lowering sea level

• Known as isostatic recovery

Accretion- isostatic change

• Increase in land build up due to deposition of sediment- pressing down land

• This increases sea level

Subsidence- isostatic change

• Land lowering due to increased deposition weighing down the sediment, over abstraction of groundwater cause land to sink

• Causes sea levels to rise

• E.g. Venice is sinking

Submergent coastline features

• created when sea levels rise and flood the land

• Include rias, fjord, Dalmatian coast

Ria- submergent coastline feature

• It’s a river valley flooded with water

• Have a V shaped cross section

• deep at mouth and narrower and shallower inland

Fjord- submergent coastline feature

• it’s a glacial valley flooded due to Eustatic change

• Have a U cross section, they’re ling and steep sided.

• They’re deeper inland

• Found in Norway

Dalmatian coasts- submergent coastline feature

• valleys lie parallel to each other

• They’re flooded so only the tops are visible- look like islands

Contemporary sea level

• IPCC predicts sea levels by 2100 will rise by 0.26-0.77m

• Could overcome coastal defences, create flooding

• As world warms, increase Eustatic sea level change and thermal expansion in ocean (as water warms it expands)

• Low lying cities and coastal settlements are vulnerable- climate change sea level planning already taking place.

• 75% or worlds cities are coastal

Sea level change in Kiribati- about

• Has 33 low lying islands (1m above sea level) but predicted many of them will disappear under sea in next 50 years due to ris

Sea level change Kiribati- why

• global warming- sea levels rising due to polar ice sheets melting and thermal expansion

• Climate scientists say by 2100, sea levels will rude between 30cm-1m