- Describe the geomorphology of the deep ocean basins.
There is very little sediment in deep ocean environments. Sediment that IS there is fine grained and occurs as thin horizontal beds. This sediment blankets the ocean floor.
- How are wind generated waves created on the ocean?
Waves are a disturbance of the surface of a body of water caused by air moving over its surface.
Energy of the moving air is transferred into the water to create a wave.
(wind speed and wind direction are both factors that control the formation of a wave.)
- FETCH
This is the body of water the wind blows over.
Bigger fetch, bigger wave.
- What are the three factors that control the formation of a wave?
Wind speed
Wind direction
Fetch
- Using a diagram describe the features of a wave (i.e wave height) including the pattern of circulation beneath a wave crest.
(SEE DIAGRAM)
- What is wave interference?
This happens when different wave patterns meet and combine.
- Briefly explain (wave interference) using one example.
Two waves that are in phase combine or interfere in such a way that the crest is twice as tall (the two crests add) and the trough is twice as deep (the two troughs add)
This is positive or constructive interference.
- What is wave reflection?
This occurs when a wave bounces off an object.
Often the only thing that is changed is wave direction.
(see diagram)
- What is wave refraction? (DIAGRAM)
This happens when a wave bends around an object.
- (A) As a wave approaches an object, they slow down and bunch up (wavelength is reduced)
- (B) the waves move on without any change due to the object
- As a result, the wave bends or refract around the island. Wave energy is focused on the part of the island that faces the waves and erosion increases.
- In the sheltered lee side of the island, at (C), there is a drop in water energy as turbulence increases. More deposition takes place here.
- Briefly explain how a wave becomes more parallel to a shoreline as it approaches the shoreline (DIAGRAM)
- As the part of the wave at (A) enters shallow water it contacts the bottom and slows down.
- At (B) the wave continues at it’s original speed.
- As a result, the entire wave bends in such a way that it becomes parallel to the coast.
- Briefly explain how a long shore current is generated by waves at a shoreline. (DIAGRAM)
A (A), the waves strike the shoreline at an angle as it breaks. Water rushes up on shore and goes to zero velocity.
At (B), the water returns straight back offshore.
At (C) the returning water is redirected back on shore by the next incoming wave
The water returns back offshore again and the process repeats itself over and over.
The result is a longshore current - the flow of water parallel to the shoreline.
- Plunging Wave (diagram)
The top falls over. These waves happen most often on steep beaches.
- Surging Wave (diagram)
Entire wave front advances as it breaks. These waves happen most often on steep beaches.
- Spilling Wave (diagram)
Top falls down the front. Waves tend to occur on a beach with a shallow gradient.
- What is a beach?
A sedimentary deposit at a coastline created by waves.
- What is the difference between a winter beach profile and a summer beach profile? SUMMER
In summer, the movement of water onshore carries sediment onto the beach. However, because summer waves are smaller, the return flow is weak and sediment is not carried back offshore.
It remains at the high water mark to create the summer profile.
- How do multiple bars form in the breaker zone?
You get different waves breaking at different times.
Off shore bars are deposited by the action of breaking waves.
When waves break at different places and times (because they are different) they can produce more than one bar.
On gently sloping shorelines the same wave can break more than once as it breaks, reforms and breaks again resulting in multiple bars.
- BAR
A bar is a ridge of sediment that is created as a result of breaking waves.
- What is an Edge Wave? How does it form?
An edge wave is a wave that travels parallel to the shoreline.
The crest of an edge wave is perpendicular to the shoreline.
Edge waves are wind generated waves.
- Edge Wave Travel
Edge waves are wind generated waves.
They travel parallel to the coast because that was the direction the wind was blowing. They may also travel parallel to the coast because of wave refraction.
- What is a beach cusp?
A beach cusp is a regular pattern of sediment distribution in the swash zone that includes a raised “horn” and low “embayment.
- How does a beach cusp form?
Along a coastline there can be two patterns of waves. At C these two wave crests meet to make one larger crest (positive interference).
At D, two wave troughs meet to make one lower trough (positive interference).
A- larger waves breaking further on shore
B- smaller waves breaking lower on the shoreline
As a result of wave interference there is an alternating pattern of larger (A) and smaller waves (B) breaking on the shoreline.
The larger waves create the low embayments composed of finer sand and the combination of return flow from the embayment and the smaller waves create the horns and the corse sediment in them.
- What is a spit?
An extension of the coast and beach into deeper, offshore water.
- How does a spit form?
A a longshore current moves sediment along the coast to form a beach. Where the coast changes direction the long shore current may continue to into deeper, offshore water. Sediment continues to be deposited as current velocity decreases. The result is a spit.
