Coastal Landscapes and Processes Flashcards
The coastline is where…
land meets the sea
Coastal erosion involves the action of..
waves wearing away the rocks along the coastline and removing the coastal sediments
What are the four main processes of coastal erosion?
- hydraulic action
- abrasion
- solution
- attrition
hydraulic action
when waves crash against the cliff, the impact, force and weight of the water against the rocks wears away the rocks
What does hydraulic action also do to joints and faults in the rock
compresses air into the joints and faults, causing pressure to build and loose rocks to be dislodged
As the waves retreat in hydraulic action, what happens to the rock
the compressed air is released, often explosively, causing the rock to weaken further
Abrasion
fragments of rock, pebbles and sand are picked up by the waves and thrown against the cliff face, causing pieces of rock to break off
Solution
chemical action on rocks by seawater.
What is solution most effective on?
limestone rocks, in which calcium is dissolved and carried away in solution
Attrition
rock fragments and pebbles carried by the waves are reduced in side as they collide against each other and the cliff face
During attrition, the rocks are eventually broken down eventually into…
sand-sized particles, which are more easily transported by waves
What is weathering
the break down of rocks at or near to the surface of the ground
What are the three key weathering processes?
- mechanical (freeze thaw)
- chemical (acid rain)
- biological
Mechanical / freeze-thaw
- repeated freezing + thawing of water in a crack or hole in a the rock
- water expands by 10 % when frozen -> stresses within the rock
- ice melts, water seeps deeper into the rock along the deepened crack
chemical weathering
rainwater-slightly acidic
-when rain falls on rocks such as limestone and chalk, a weak chemical reaction takes place
Biological weathering
the roots of growing plants can widen cracks in rocks + burrowing animals and nesting birds on cliff faces
What is mass movement
the down slope movement of rocks and soil from the cliff top under the influence of gravity
What are rock falls?
when pieces of rock from a weathered cliff fall
When does rock falls occur?
as the rock at the base of the cliff has been undercut by the actions of the waves, leaving the rock above unsupported and causing it to collapse
When does slumping often occur?
after long periods of rainfall
What happens in slumping
The rain seeps through permeable rocks such as sandstone
At the junction where the permeable rock meets an impermeable rock such as clay, how does slumping happen?
the saturated soil and weaker rock slumps and slides in a rotational manner along a curved surface
How is sliding different to slumping?
the movement of material occurs along a flat surface; usually a bedding plane
In sliding, large amounts of…
soil and rock move down slope rapidly and can cause a lot of damage
What are the three types of mass movement?
rock falls
slumping
sliding
What are the four types of transportation
traction
saltation
suspension
solution
what is longshore drift?
the transport of sand and pebbles along the coast by waves
What is traction
large boulders are rolled along the seabed by waves
What is saltation
small boulders are bounced
What is suspension?
sand grains are carried
What is solution
carries dissolved lime from limestone and chalk rocks
When does deposition occur?
when there is not enough energy to carry the eroded materials any further
How are waves generated?
wind blowing over the sea
What does the friction with the wind and the surface of the water cause?
ripples to form, which grow into waves
Height and energy of waves are determined by..
- wind and strength
- wind duration
- fetch
What is fetch?
the distance of open water over which the wind has been blowing
How does a longer fetch affect the power of the wave?
the more powerful wave
What is wind duration?
the length of time the wind has been blowing
The stronger the wind…
the greater the friction on the surface of the sea- the bigger the wave
As a wave approaches the shore, what happens to the base of the wave?
slowed by friction with the sea bed, but the upper part continues to travel forward
The water that surges up the beach until it runs out of energy is called what?
swash
The water that then runs back down the beach under gravity is called what?
backwash