Sea Level Change Influences the Coastline Over Time

Longer-Term Sea Level Changes

Eustatic & Isostatic

• Eustatic → Change in sea level

• Melting ice causes more water in sea so sea level rises

• In glacial periods, much more water stored on land in form of ice so sea levels lower

  

• Isostatic → Change in land level (often linked to ice on land)

  • Glaciers can be kms thick so weight forces the land downwards
  • When glaciers melt - isostatic rebound as less weight on land so land rises again

Tectonic

• As tectonic plates move & collide, some continental shelves & areas of land are either pushed upwards or sink downwards
  • Tends to be a localised event

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Emergent Coastlines

🔗 Often a result of isostatic rebound

• Raised beach → A former beach that is now above the high tideline (eg. on the Isle of Arran, Scotland)

  • Some of these have different levels ∴ indicating different stages of uplift

• Fossil cliffs → Cliffs no longer being eroded as isolated from the sea

  • Fossil features such as former cave & stacks are left above on raised marine platforms

Submergent Coastlines

🔗 Often as a result of sea level rise (eustatic rise) or isostatic sinking

• Ria → Frowned winding river valley w/ offshoots of water stretching inland
  • Widest & deepest nearest the sea, gets narrower & shallower inland

• Fjord → Straight, glaciated valleys that were drowned by rising sea levels at the end of the ice ages (eg. in Norway)
  • Has very deep water with steep sides

• Dalmatian coasts → Concordant coasts where the sea has flooded the landscape of alternating hills and valleys to create long bays and parallel hilly islands