Coastal Transport And Deposition Flashcards
What are the types of transport?
LSD
Tides and currents
What is LSD?
Most waves approach a beach at an angle- generally from the same direction as the prevailing wind.
As the waves advance, material is carried up the beach at an angle.
The backwash then pulls material down the beach at right angles to the shore.
What does LSD do?
Transports material along the beach.
What are tides?
Changes in the water level of seas and oceans - caused by the gravitational pull of the moon and, to lesser extent, the sun.
What is tidal range?
Relative difference in height between high and low tides.
High tidal range = creates powerful tidal currents, as tides rise and fall.
Tidal currents can become particularly strong and fast in estuaries and narrow channels, and are important in transporting sediment.
What are the types of marine transport?
Traction
Saltation
Suspension
Solution
What is traction?
Relatively large and heavy rocks are rolled along the seabed
What is saltation?
Smaller and lighter rocks bounce along the seabed
What is suspension?
Lighter sediment is carried
What is solution?
Dissolved sediment is carried
When does deposition occur?
When waves no longer have sufficient energy to continue to transport material
How does deposition occur?
Gravity settling
Flocculation
What is gravity settling?
Occurs when the energy of transporting waters becomes too low to move sediment.
Large sediment will be deposited first, followed by smaller sediment
What is flocculation?
Small particles will remain suspended in water.
Particles will clump together through electrical or chemical attraction, and become larger enough to sink
What are the types of coastal depositional landforms?
Spits Different types of beaches Offshore bars Bars Tombolos Cuspate forelands
What are spits?
A long narrow feature, made of sand or shingle, which extends from the land into the sea (or part way across an estuary).
How are spits formed?
It’s moved along the coast by LSD.
If the coastline suddenly changes direction (e.g. because of a river estuary), sediment will begin to build up across the estuary mouth and a spit will start to form.
The outward flow of the river associated with the estuary will prevent the spit from extending right across the estuary mouth.
What is a recurved spit?
The end of a spit will begin to curve round, as wave refraction carries material round into the more sheltered water behind the spit.
What may happen behind a spit?
A salt marsh may develop, where finer sediment settles and begins to be colonised by salt-tolerant plants
What are offshore bars?
Also known as sandbars, are submerged (or partly exposed) ridges of sand or coarse sediment - created by waves offshore from the coast.
How are offshore bars created?
By waves offshore from the coast
Destructive waves erode sand from the beach with their strong backwash and deposit it offshore in bars.
What are bars?
Where a beach or spit extends across a bay to join two headlands
What can happen behind bars?
They can trap water behind them to form lagoons.
What are tombolos?
A beach (or ridge of sand and shingle) that has formed between a small island and the mainland