Coastal Formations Flashcards
Discordant coastline
Coastline and geology are at right angle to each other
Concordant coastline
Coastline and geology are parallel to each other
Wave refraction
Waves undergo a change in direction as it approaches headlands and bays
El nino
A reverse in an ocean current in the South Pacific Ocean
Headland and bay formation
-require a discordant coastline where geology consists of alternating bands of hard and soft rock which face at right angle to the sea
-destructive wave erode coastline via erosional processes
-harder rock erodes slower and sticks out from the fast eroding soft rock
-this is a headland
-the bay is formed when soft rock is eroded backwards
-wave refraction then takes place and creates a beach in the bay
How does wave refraction create a beach within a bay
Wave energy is concentrated onto the headland, meaning the bay receives low energy waves (constructive) which pushes sediment up due to its larger swash than backwash
Stack formation
-weathering processes such as salt crysallisation weaken rock face
-headland is attacked by destructive waves which have been refracted onto it
-waves attack the base of headland by series of erosional processes
-waves strip away material by throwing rocks at the headland (abrasion)
-processes create a geo in the headland
-overtime the geo becomes a cave
-continued erosion eats away material and forms an arch
-arch is weak and collapses from gravitational forces
-leaves a vertical column of rock called a stack
What is a geo
A small hole in the rock face from erosional processes such as abrasion of hydraulic action
What are the inputs of energy for a stack
-Gravitational energy (causes arch to collapse)
-Destructive waves (erode the headland)
-Wind energy (creates high energy waves)
-tidal energy
What are the inputs of matter for a stack
Rocks in water used in abrasion
What processes occur in the formation of a stack
Weathering
Erosion
Mass movement
Wave refraction
What are the components of a stack
Geo
Cave
Arch
Headland
Stack
What sources of beach material are there
-river (90%)
-offshore (5%)
-cliff erosion (5%)
What is a beach
An accumulation of material deposited between positions of high and low tide
Inputs vs outputs
The inputs of material must be greater than outputs for a beach to form
What gradient do sand beaches have
Gentle (5°)
What gradient do shingle beaches have
Steeple (10-20°)
What waves are needed to produce shingle beaches
High energy, as the material is larger
What type of beach profile do destructive waves form
Shallow flat beaches, the backwash is stronger than swash so material is eroded from the beach
What beach profile do constructive waves form
Steep beaches, as swash is higher than backwash so material gets deposited onto the beach
How is a sandy beach formed
Usually formed in sheltered bays where low energy constructive waves transport material onto the shore, the swash is higher than the backwash so so material is moved up the beach.
What is a berm
A small ridge that develops at the position of high tide resulting from deposition at the top of the swash
