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How do coastal landforms evolve over time as climate changes? - Coggle…
How do coastal landforms evolve over time as climate changes?
Eustatic changes: changes in the volume of water in the global ocean store.
These changes are affected by a mean change in global temperatures, which effects:
The density of water in the ocean store
The amount of water in the global ocean store
Factors that affect global temperature (that then affect sea levels):
Variations in the earths orbit around the sun (every 400,000 years)
Variations in the amount of energy produced by the sun (with a solar maximum every 11 years)
Changes in the composition of the atmosphere due to major volcanic eruptions
Variations in the tilt of the earths axis (every 41,000 years)
Emergent coastal landscapes form as sea levels fall.
How sea levels fall:
With colder temperatures, precipitation is more likely to fall as snow, which turns to ice and means water is being stored on land in solid form, instead of liquid, meaning sea levels fall.
As temperatures fall, water molecules contract and the density of the ocean decreases (estimated that a 1 degree fall causes sea levels to fall 2m because of a reduction in density)
Emergent landforms
Landforms which are shaped by wave processes during times of high sea level are exposed when sea levels fall. As a result they may be found far inland. These landforms include:
Raised beaches: former shore platforms that are left at a higher level than the present day sea level. Often found far inland from the present day coastline
Marine terraces: forms in a similar way to a raised beaches, which are usually localised and usually are at the base of an abandoned cliff. Marine terraces are usually a lot larger.
Abandoned cliffs: typically found behind beaches, left behind with erosional landforms such as wave - cut notches, caves and maybe even arches and stacks.
Modification of these landforms:
These landforms continue to be affected by weathering and mass movement even though they are not affected by wave processes.
With climate change, sea levels could rise again, which means they could be close to or even exposed to wave erosion again.
Most types of weathering continue to take place, such as physical weathering (freeze thaw), biological weathering from plants/trees, and chemical weathering from animal litter.
Submergent coastal landscapes form as sea levels rise.
How sea levels rise:
An increase in global temperature leads to higher rates of melting of ice stored on land, such as in ice sheets, ice caps and valley glaciers.
This leads to an increase in the volume of water stored as water in the ocean.
As temperatures rise, water molecules also expand and this leads to an increased volume.
List of submergent landforms
Rias
Rias are submerged river valleys formed as sea levels rise.
The lowest part of the river and the floodplains are usually completely drowned, while the upper section of the valley and river remains exposed.
Example: Salcombe
Fjords
Submerged glacial valleys with steep, cliff - like valley sides.
Much deeper than rias with steeper cliff faces
Formed by the melting of glaciers around it
Formed in glaciated environments, U shaped valleys
Shingle beaches
Modification of these landforms
Wave processes: affecting rias and fjords at present day sea level.
Sub - aerial processes on the djord/ria face: which may make the sides less steep.
Shingle beaches being affected by longshore drfit.
Marine erosion increasing due to stormier conditions and larger waves