Coasts Flashcards
What are properties of constructive waves?
- weaker winds
- short fetch
- low energy
- swash stronger than backwash
- deposition greater
- low waves
- long wave length
- 6-9 waves per minute
What are properties of destructive waves?
- strong winds
- long fetch
- high energy
- backwash stronger than swash
- erosion greater
- high waves
- short wave length
- 11-15 waves per minute
What is wave length?
The distance between wave crests
What is wave height?
The height from the wave trough to the crest
What is wave frequency?
The number of waves per minute
What is a crest?
The highest point of a wave
What is a trough?
The lowest point of a wave - the general sea level
What is fetch?
The distance in which waves are formed
What is swash?
Water rushing up the beach
What is backwash?
Water draining down the beach
What do the height and strength of waves depend on?
- wind speed
- the time the wind blows for
- fetch
How does longshore drift occur?
- waves approach the beach at an angle similar to that of the wind
- swash along the beach at angles - sea carrying sediment
- backwash at right angles to the beach
- beach material builds up
What is corrasion/abrasion?
The process where the coast is worn down by material carried by the waves - particles are thrown against the rock
What is hydraulic action?
When waves enter faults and compress air within the crack. When the wave retreats the air in the crack expands
What is attrition?
When material carried by the waves bump into each other so are smoothed and broken down
What is corrosion?
The chemical action of sea water where acids the salt dissolve rocks on the coast
What are the coastal processes involved in shaping the coast?
- wave erosion
- weathering (i.e. at top of cliff)
- mass movement (e.g. slumping, landslides, flowage)
- transportation (longshore drift)
- deposition
What types of weathering are there?
- mechanical
- biological
- chemical
Types of mechanical weathering?
- freeze thaw - jagged rock faces
* salt crystallisation
What is salt crystallisation?
- when salt crystal growth occurs in rock pores
* expanding crystals cause walls to crack
Where does salt crystallisation occur?
Only in coastal environments due to salt in the sea
Example of chemical weathering?
Acid rainwater - weak carbonic acid in rain dissolves rocks (solution)
Example of biological weathering?
Burrowing animals and plant roots cause rocks to loose and crack
What is mass movement?
The down hill movement of loose material under gravity