Coastal Processes Flashcards
How do waves form?
Wind waves are caused by friction and pressure on the sea’s surface from the wind.
How do tidal waves form?
Tidal waves are caused by gravity, mainly from the moon.
How do tsunamis form?
Tsunamis are caused by geological disturbances such as earthquakes, volcanic eruptions etc
What kind of waves are very large?
Destructive waves
What kind of waves are small?
Constructive waves
Characteristics of a constructive wave:
-strong swash
-weak backwash
-wave crests far apart
-gently sloping wave front
-breaking wave spills forwards
Destructive wave characteristics:
-strong backwash
-waves close together
-steep wave front
-breaking wave plunges downwards
Wave length of destructive waves:
Under 20m apart
Wave height of destructive waves:
Over 1m in height
Wave frequency of destructive waves:
10-15 per minute
Swash of destructive waves:
Weak
Back wash of destructive waves:
Strong
Dominant process of destructive waves:
Erosion
Wave length of constructive waves:
Over 20m apart
Wave height of constructive waves:
Under 1m in height
Wave frequency of constructive waves:
6-10 per minute
Swash of constructive waves:
Strong
Backwash of constructive waves:
Weak
Dominant process of constructive waves:
Deposition
What is transportation?
The movement of sediment from one part of the coastline to another.
What is weathering?
Sub-aerial processes (such as rain) wearing away rock over time.
What is erosion?
The action of the waves causing the coastline to wear away.
What is mass movement?
The bulk movement of soils or rock down hill.
What is hydraulic action (also known as “water on cliff”)?
The water traps air in cracks and caves in the rock. This air is compressed by the incoming waves placing great pressure on the rocks, causing them to eventually crack.
What is attrition (also known as “rock on rock”
Particles carried by the waves crash against each other and are broken up into smaller rocks.
What is abrasion (also known as rock on cliff) - sand paper effect?
Particles carried by waves crash against the cliffs, eroding the cliffs.
What is solution( also known as “chemical on cliff” )
Salt in the seawater slowly dissolves the cliffs. The material produced is carried away by the process of solution.
What is chemical weathering?
Acidic rainwater dissolves chalk and limestone.
What is biological weathering?
Plant roots get into cracks and expand.
Animals dig into and burrow into the rocks.
What is mechanical weathering?:
Water builds up in the cracks. When it gets cold the water freezes causing the water to expand, then as it gets hotter, the ice melts and seeps deeper into the rock causing the rock to weaken.
Sea water with salt goes into the rock, when the water leaves, salt crystals left behind expand causing the rock to break.
What is a mudslide?
Rainwater saturated into the dirt makes the dirt heavier and easier to fall down so it causes a mudslide
Unsaturated soil “flows downhill”
-at the bottom of the cliff s lone forms
What is a landslide
-the mass movement of rock down a cliff or hill
-can happen due to weathering
What is rockfall?
-Occurs on steep cliffs
-fragments of the rock break away from the cliff due to weathering
E.g freeze thaw
What is longshoreman drift?
-Long shire drift is the movement of material along the shore by wave action
-waves approach the beach at an angle determined by the prevailing wind
-the swash (waves moving up the beach) moves material up and along the beach.
-the backwash (waves moving back down the beach) moves material back at a right angle
-contributes to the formation of landforms -e.g- a spit
How do steep cliffs form?
Steep cliffs are formed when hydraulic action and abrasion erode the base of a cliff due to destructive waves.
-If there is softer rock then this will erode faster, leaving hard rock
-chemical,biological and mechanical weathering also weaken the tips of cliffs, causing rockfall to occur
-overtime The steep cliffs will retreat
Characteristics of the upper course
-steep gradient
-vertical erosion
-landforms of erosion
-low discharge
-shallow + narrow channel
-velocity is lower than middle/lower course
