Temporal Variations And Their Influence On Coastal Enviroments Flashcards
How are tides created?
Tides are created by the gravitational effect of the moon which pulls water on Earth towards it to create high tides with a balancing increase of seas on the opposite side of the earth
Where is the sea level lowest ?
The opposite side from where the moon is
What can movements of the sun moon and earth change ?
The gravitational pull on earth and the tides
What happens Twice a month in relation to tides ?
The sun earth and moon are aligned which results in a gravitational pull at its greatest creating higher than average tides called spring tides
What happens when the sun and moon are at right angles to each other?
The gravitational pull is weak creating a Lower than average tide called neap tides
What is the tidal range ?
The difference in height between high and low water during the Monthly tidal cycle it influences the zone where coastal processes occur
What are offshore and onshore currents ?
Flows of water occurring in the coastal zone
What are Tidal currents
Where water floods the intertidal zone at high tide, moving and depositing sediment. As the tide falls ( ebb tide ), sediment moves in the reverse direction
What are shore normal currents ?
Waves aligned parallel to the coastline pushing water straight up the beach. Water returning directly away from the shore can form strong, fast-moving channels of water called rip currents
What are long shore currents?
Waves approach the shoreline at an oblique angle but return straight down the beach, moving sediment parallel to the shore
How is a wave formed?
By the transfer of energy from the wind blowing over the sea surface.
How do stronger winds effect waves?
They increase frictional drag and the size of the waves
What are the 2 types of wave?
Constructive and Destructive
What are the qualities of a constructive wave?
Strong swash
Sediment is pushed up the beach
What are the qualities of a destructive wave?
Wave “plunges”
Strong backwash
Steep beach profile
Sediment is eroded and deposited offshore
What type of wave is higher ? Destructive or Constructive?
Destructive (Greater than 1m)
What wave is longer? Destructive or Constructive?
Constructive (up to 100m between crests Destructive is 20m)
Which wave has a longer period? Destructive or Constructive?
Destructive (10-14 breaking each minute) Constructive=6-8
Which wave is steeper? Destructive or Constructive?
Destructive (plunges whereas constructive spills over)
Which wave has the most energy?
Destructive has higher energy
Which wave has stronger swash?
Constructive
Which wave has a stronger backwash?
Destructive
What is swash?
The turbulence in the water that carries sediment.
The swash makes the water wash up on the beach
What is backwash?
When the water runs back down the beach.
Brings sediment offshore.
Where do constructive waves move material?
Up beach to form a berm
Where do destructive waves move material?
Down beach
What does a constructive wave do to beach gradient?
Increases the gradient of the upper beach
What does a destructive wave do to the beach gradient
Steeper upper beach and gentler lower beach
What is the crest of a wave?
The crest is the peak of the wave
What is the wave length?
Distance between each crest
What is the wave amplitude?
Distance from crest to centre of wave
How would you work out the steepness of a wave?
Wave steepness= wave height / wave length
What is the wave height?
The vertical distance between the crest and the trough
What is a trough?
The bottom of a wave between 2 crests
What is the wave period?
Time interval of wave motion from trough to trough in seconds.
What is the wave base
Half the wave length below the wave where there is no water movement
How do water particles move along the wave?
In an orbital path at any one moment
When are destructive waves more common and why?
During the winter because of stormier weather. This is due to the jet stream steering more Atlantic depressions over the UK during winter. Atlantic depressions are more frequent and intense during winter months
