Deck 18b- Transportation, depositional processes and landforms Flashcards
What is transportation?
Transportation is the movement of eroded material along a coastline.
What are 4 types of transportation?
Traction, saltation, suspension, solution
What is traction?
Where pebbles and larger material are rolled along the sea bed.
What is saltation?
Where small pieces of shingle or large sand grains are bounced along the sea bed.
What is suspension?
Small particles such as silts and clays are suspended in the flow of the water.
What is solution?
When minerals in rocks like chalk and limestone are dissolved in sea water and then carried in solution. The load is not visible.
What does aerial transportation mean?
Movement of sediment by the wind.
What does marine transportation mean?
Movement of sediment through marine processes.
What does fluvial transportation mean?
Movement of sediment through river processes.
What is longshore drift?
The zigzag movement of sediment along the coastline.
How does longshore drift occur?
Swash brings sediment onto the beach in the direction of the prevailing wind. Backwash then transports the sediment back to the sea vertically (controlled by gravity). Another wave then transports the sediment back up the shore at an angle. As the processes repeats it causes the sediment to be movement along the beach.
What controls the direction of longshore drift?
Prevailing wind direction
Why are coastlines with high level of longshore drift vulnerable to erosion?
When the beach material is being lost through longshore drift, the coastline in that locality is likely to be worn back more quickly because the buffering effect of the beach is lessened.
What is terminal groyne syndrome?
When groynes (structures built out to sea perpendicular to the shoreline) are constructed they can disrupt longshore drift. Material builds up against the groynes as it is transported along the shore via longshore drift. This helps to build up the height and width of the beach where the groyne has been constructed. However it can starve the coastline further along the beach of sediment leading to higher rates of erosion. This is known as terminal groyne syndrome.
What is deposition and why does it occur?
Deposition is when material being transported by the sea is dropped due to a loss in energy. Deposition occurs when the sea transporting sediment loses energy and slows down.
When is deposition likely to occur?
-Waves enter an area of shallow water.
-Waves enter a sheltered bay, creating beaches.
-There is little wind.
-When a river flows into the sea reducing wave energy.
-There is a good supply of sediment nearby.
What are the characteristics of a shingle beach?
Steep gradient profile, more exposed, often have a storm beach composed of larger material. Higher energy waves remove the sand leaving the pebbles (shingle).
What are the characteristics of a sandy beach?
Usually form in sheltered bays where constructive waves dominate. Strong swash brings large amounts of sediment onto the shore creating a series of smaller berms. Sandy beaches have a gentle profile and gradient.
What is a spit and how does it form?
A spit is a long, narrow feature made of unconsolidated sediment that stretches out from land into the sea or across an estuary. Longshore drift transports sediment along a coastline until the coastline changes shape e.g it reaches a sheltered bay or estuary. Over time sediment is deposited and builds up. Longshore drift continues to supply more sediment allowing the spit to develop and stretch further across the estuary. The flow of a river will prevent the spit from stretching all the way across an estuary. Wave refraction can cause a spit to curve at the end creating a recurved spit.
EXAMPLES: Poole, Swanage Bay area (Dorser) or Spurn Head, Holderness Coastline
What is a bar and how do they form?
Bars form where a beach or spit extends the whole way across a bay to join two headland. These can only form where there is no major river flow. Bars straighten coastlines and create sheltered areas called lagoons behind them.
EXAMPLE: Slapton Ley, Devon
What is a tombolo and how do they form?
A tombolo is a beach that extends outwards to
join with an offshore island. This occurs when a
spit continues to extend and reaches an island.
EXAMPLE: Chesil beach, in Dorset, links Isle of Portland to the mainland
What is a cuspate foreland and how do they form?
These are low lying triangular-shaped
feature that extend from the shoreline
formed from deposited sediment. They form
when longshore drift occurs in two
directions which bring sediment in from
opposite directions and converge at the
boundary of a sediment cells.
EXAMPLE: Dungerness, Kent
What is an offshore bar and how do they form?
Offshore bars are submerged (or partially exposed) ridges of sand/shingle created by waves that operate off the coastline. Destructive waves with a strong backwash remove sediment from the beach and deposit it offshore which over time creates these offshore bars.
EXAMPLE: Scroby Sands, Norfolk. They have now constructed wind farms on it
