Sea level change and landforms

Sea level change in three ways

Thermal expansion

Melting of ice

Isostatic processs

Diffrence between isostatic and eustatic

Eustatic: Physical chjange in the level of the water - Global

Isostatic: Change in the height of the land relevant to the water - Local

Why is there significant sea level change over time

Milankovitch cycles which drive

Glacial and interglacial periods

How can overall eaustatic change be altered in some places

Localised isostatic change cna:

Decrease the rate by rising or falling alongside

Entirely oppose the change, if the isostatic rate is higher than the eustatic, rise up out of sea

How does isostatic change work?

Ice is on the land, heavy and compress the land down

Ice melts, land still compressed

Isostatic recovery leading to isostatic uplift causes the land to expand back upwards

Submergent features

Ria

Fjord

Submergent features driven by

Eustatic change

Ria - 4 step process

River valley is formed

Widened and flattened by sediment load

Submergent eustatic sea level rise takes place

Floods the floodplain and river valley

Floods the lower and middle course

Ria example

Bantry Bay, Ireland

Fjord

U shaped glacial valley is formed during glacial movement

Glacier melts and drops sediment at entrance to Fjord

Submergent Eustatic sea level rise over the sediment and floods the valley

Leads to a Fjord, shallow at inlet and deep wide U shaped flooded valley

Example of Fjord

NordFjord in Norway

Dalmation Coast

Mountain range runs parallel to coast

Submergent Eustatic sea level rise rises over the bottom of the valleys

Floods the valley in between the moutains

Leads to exposed island ridges (previously tops of mountains) that run parallel to coast)

Example of Dalmatian Coast

Dalmation Coast in Croatia

Feature named after this place!

Emergent features driven by

Localised isostatic sea level change

The land rises up out of the sea due to isostatic recovery and uplift

Raised beaches

Wave cut platform is formed between high and low tide

This wave cut platform rises up out of the sea

At the back there may be relic cliffs - previously high tide line

Very prominent in Northern Scotland

Can leave exposed festures usch as stacks, stumps, caves and relic cliffs

Relict cliffs

The previously cliff that marked the high tide point

Whihc has now risen out of the sea

For these features to occur

Isostatic uplift rate > Eustatic sea level rise

Example of raised beach

Drumadoon in Scotland

Typical height for a raised beach / terrace above the high tide mark?

Between 2 and 15 metres

Marine terrace difference

A marine terrace is similar to a raised beach

But it is not created by an original wave cut platform

Rather a continuous gently sloping inshore or offshore

Not a distinct feature with landforms that drops off

Gently risen up out of sea