L4 - Coastal Conveyor Belt Flashcards
What determines the angle at which a wave hits the shore in Longshore Drift?
Prevailing Winds
What is the difference between swash and backwash?
Swash carries particles up the beach at an angle, whereas backwash returns the particles to the sea, which follows the angle of the slope under gravity
Is wave energy focused on headlands or bays as a result of wave refraction?
Wave energy converges on HEADLANDS, and this absorbs some of the energy so that as the sediment moves either side towards the bays, there is a low energy environment in bays.
Which type of wave is associated with strong winds and long fetches, where the backwash is much stronger than the swash?
Destructive waves - narrow and steep beaches, so do not offer much protection to erosion as they cannot absorb wave energy
Which type of wave is associated with light winds and short fetches, where the swash is much stronger than the backwash?
Constructive waves - wide and shallow beaches, so can offer protection to erosion as they can absorb wave energy
What is hydraulic action?
This occurs when large waves break against a cliff (to remember think of hydro - water, which must mean waves!) The waves compress air into the cracks, and when the water falls the air is released explosively and shatters the rock.
What is attrition?
This occurs when pieces of rock are moved by the waves and knock into each other, causing them to become smaller and rounder. They eventually turn into sand.
What is abrasion?
This occurs on a cliff, or other exposed areas of rock, when waves pick up sand and pebbles and scrape them against the surface (to remember think of rubbing together sandpaper and wood)
What is solution/corrosion?
This occurs when seawater dissolves some of the rock minerals, causing the disintegration of rock ( to remember think of solutions and dissolving in chemistry)
Give an example of a location that has a spit, and an example of a location that has a sand bar
Spit - Hurst Spit
Sand bar - Slapton Sands
How is a spit formed?
Formed by longshore drift of sediment past the point where the land has a sudden change in direction (>30°). Most form at the mouths of rivers, which do not allow sediment to reach the other headland)
When does a spit become re-curved/hooked?
As a spit forms and alters the coastline, the waves are refracted which causes secondary deposition via the new wave angle. In addition, there is a change in wind direction.
How is a bar formed?
Formed by the continuation of the LSD process, until it reaches the other side to form a bar/barrier beach.
What did the bar in Slapton create?
The former bay was cut off from the sea to form a lagoon (Slapton Ley)
When is a tombolo formed?
Only when a spit joins an offshore island
