3.1.3.3 Coastal Landscape Development Flashcards
Estuarine Mudflats and Saltmarshes
Deposition occurs in river estuaries as water velocity is low so the water can no longer carry its sediment in suspension. Mudflats/marshes may also occur in sheltered areas such as behind a spit.
Deposition occurs as a result of flocculation.
A positive feedback loop operates, amplifying the initial deposition as submerged and semi-submerged plants trap more sediment and reduce water velocity leading to increased deposition.
This leads to mud above the high tide level.
Pioneer plants colonise the transition zone, leading to more sediment becoming trapped.
A meadow is formed as sections of the salt marsh rise above the high tide level, leading to the climatic climax of the vegetation succession when trees begin to colonise the area.
Isostatic Change
Isostatic change occurs when the land rises or falls relative to the sea and is a localised change.
Isostatic sea level change is often a result of isostatic subsidence. When the glaciers melted, this lead to isostatic recovery and the coastline to rebound and rise again in the areas that were covered by ice.
Eustatic Change
Eustatic change affects sea level across the whole planet. Eustatic change may be due to thermal expansion/contraction or changes in glacial processes.
Thermal expansion is the process of water expanding when it gets warmer, and so the volume of water increases leading to rising sea levels.
Emergent Coastal Landforms
Where the land has been raised in relation to the coastline.
Submergent Coastal Landforms
Landforms of submergence occur when the sea level rises or the coastline sinks in relation to the sea.
Fjords
Fjords are an example of a Submergent landform
A fjord is formed when a glacier retreats, after carving its typical U-shaped valley
The U-Shaped valley is formed by processes such as plucking and abrasion by the glacier
They are relatively steep and narrow with very steep sides
They have a shallow mouth caused by the threshold formed by deposition of material by the glacier.
They are very deep further inland
Water fills the valley due to rising sea levels relative to the land, creating the fjord
Recent and Predicted sea level change
Since records began around 20,000 years ago, sea levels have always been rising from 120m below the levels which they are now at today.
Sea level increase slowed around 8,000 years ago and levelled at the current height around 3000 years ago.
Since 1880 sea levels have increased by around 21-24cm.
The International Panel on Climate Change (IPCC) predicts that sea levels may rise between 0.3 - 1.0m by 2100.
Impacts of sea level rise
Possibly cause aquifers to be polluted in low-lying atoll islands.
It may also inundate many coastal cities and increase the risks from
tropical storms and Tsunamis.
