Coastal landscapes Flashcards
Fetch
The distance of open sea over which wind blows- a long fetch will give bigger waves than a small one.
What happens when a wave nears a coast?
As it nears the coast the sea bed slows down the bottom of the wave due to friction. The circular orbit becomes more oval creating a crest. The crest topples over and causes the wave to break.
Swash
The forward movement of water up the beach
Backswash
The backward movement of water after the wave has broken.
What are the main types of waves
Constructive
Destructive
Destructive wave
High wave height
Weak swash
Powerful backwash
Short wave length
Constructive wave
Low wave height
Long wave length
Powerful swash
Weak backwash
What are the main types of coastal processes?
Weathering Mass movement Erosion Transportation Deposition
What are the main types of weathering?
Physical
Biological
Chemical
Physical weathering
Freeze thaw- the constant expansion of water in cracks in the rock- cause large chunks to flake off
Haloclasty-Saltwater enters cracks and dries leaving salt crystals- they build up until the rock breaks apart
Biological weathering
Roots of vegetation break up the rocks
Acidic bird poo dissolves rock
Rabbits burrow through soil which allows inundation to happen
Chemical weathering
Carbonation- limestone is dissolved by acid rain
Hydrolosis- acid rain breaks down the rock by causing it to rot
Oxidation- rocks react with air
Mass movement-slumping
- Rainwater soaks into porous rock like sandstone
- The saturated rock is heavy and puts pressure on the underlying rock
- The underlying rock can’t cope with the pressure and a huge part of the cliff slips into the sea
What factors affect mass movement?
Rainfall Geology Angle of teh slope Vegetation cover Human activity
Flow
Fine loose material become saturated and flows down the slope
Fall
Freeze thaw weathering widens cracks in the cliff which then break off- forms scree slopes
Slide
Top layer of rock become ssturated and slides (under the force of gravity) over the layer of rock below
Creep
Soil particles expand and are lifted from the slope before shrinking- gravity pulls them down
Hydraulic action
The relentless force of destructive waves pounding the base of a cliff. The waves force air into cracks (this widens them) and chunks of rock fall of the cliff.
Abrasion
Destructive waves hurl rocks at the cliff slowly chipping away at it.
Attrition
During transport pebbles collide with each other and slowly shrink in size.
Solution
Some rock dissolve in seawater e.g chalk
Tides
Caused by the gravitational pull of the moon on the earth,
LSD
Occurs when the prevailing wind blows at an angle this means the swash carries sediment up the beach at an angle. The backswash transports sediment back down the beach at a right angle. It is repeated.
Factors that shape a coastline?
Geology
Sediment supply
Beach profile
Shape of the coastline
Concordant
rocks are parallel to the wave front and therefore rate of erosion are similar along the coastline
Discordant
differential erosion may occur where bands of hard and soft rock outcrop at right angles to the sea. Headlands and bays form along discordant coastlines.
Headlands and bays
Softer rocks are worn away more quickly than harder rocks. The eroded rock is deposited by the sea in bays, making the water here shallower. The harder rock puts out to sea and is called a headland. The water here is deeper
Shallower water encourages deposition. Deeper water encourages erosion.
Because the water is shallower in the bays the waves deposit material thus building up this bit of the coastline again. On the other hand, the deeper water at the foot of the headland encourages the waves to erode the coastline more and more.
