Sea Level Changes Flashcards
What are the main causes of sea level change
- climate change
- thermal expansion
- glacial and interglacial periods
Eustatic Change
When the sea level rises or falls. This is global.
In cold glacial periods, precipitation falls as snow and forms huge ice sheets. As temperatures rise, the ice sheets begin to melt and retreat and their stored water flows into rivers and the sea and so sea levels rise
Isostatic Change
When the land rises or falls, relative to the sea. This occurs locally.
During glacial periods, the enormous weight of the ice sheets makes the land sink (isostatic subsidence). As ice begins to melt, this reduced weight of the ice causes the land to readjust and rise (isostatic recovery).
Emergent landforms
Caused by fallen sea levels or rising of the land
Emergent Landform - Raised beach
Former beaches now found above current sea levels due to sea level fall or land uplift. They often have relict features like old wave cut platforms, notches, caves and arches
Emergent Landform - Marine Terraces
Stepped coastal landform formed by wave erosion at different sea levels over time. Indicate multiple cycles of sea level change where land is uplifted in stages or sea level has fallen in stages. Key features include a series of flat platforms and they are seperated by old cliff lines.
Emergent Landform - Relict Cliffs
Once active coastal cliffs but they have been left inland as the sea retreated due to isostatic rebound. Erosion processes like wave action previously shaped them but they are now weathered by sub ariel weathering. Key features like wave cut platforms, abandoned caves and arches and stacks
Emergent Landform - Coastal Plains
Coastal plains emerge when shallow sea beds are exposed due to sea level fall. These areas were once covered by waves but are now low lying flat landforms. Key features include estuaries, dunes, and marshes which are prone to flooding as they were previously below sea level
Submergent Landforms
Caused by rising sea levels or falling of the land
Submergent Landforms - Rias
Drowned river valleys formed when rising sea levels flood an unglaciated river valley. They have a winding shape, reflecting the original river system, with deeper water towards the sea and shallow water inland eg Milford Haven, Wales
Submergent Landforms - Fjords
Drowned U-shaped glacial valleys, much deeper and steeper than rias. They are formed by glacial erosion and later flooded by rising sea levels. Fjords have a shallower mouth due to glacial threshold created by deposition at the seaward end eg Milford Sound, New Zealand
Submergent Landforms - Dalmation coasts
Form when parallel river valleys are flooded, leaving long, narrow islands and inlets that run parallel to the coast. They occur in areas where folded rock structures align with the coastline eg in Croatia
Submergent Landforms - Estuaries
Estuaries are drowned river mouths where fresh and salt water mix. They are important habitats and often used for port development. eg Thames Estuary, UK
Contemporary sea level change - trends
Since records began 20,000 years ago, sea levels have always been rising from 120m below the levels they are at today. Since 1880, industrial revolution, sea levels have increased by around 235mm
Contemporary sea level change - IPCC predictions
IPCC predicts that sea levels may rise between 0.3-1.0m by 2100
Consequences of rising sea levels
- Storm Surges
- Economic Loss from reduced house prices and land prices
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