Coastal processes Flashcards
What are the 5 steps of coastal processes
Weathering, mass movement, erosion, transportation and deposition
What is weathering
The insitu (original place) breakdown of rock
What are the three types of weathering
Biological, Chemical and physical
What is biological weathering
Occurs when plants or animals break down rock
What is chemical weathering
When the chemical composition of a rock changes
Give an example of biological weathering
Trees growing in cracks of rocks and forcing it apart
Give an example of chemical weathering
When carbon dioxide dissolved in the air, carbonic acid is formed. As the acid hits rocks, some parts of the rocks that are made of calcium carbonate dissolve
What is an example of physical weathering
When there is a crease (porous/ permeable) in a rock, water fills up the gap and freezes, resulting in a 9% expansion. The rock breaks apart due to water going deeper in the crack
What is physical weathering
When physical processes affect the rock such as temperature, wind, rain and waves
What is hydraulic action
Power of water wave forces air and water into cracks which creates fractures to fault and notches that grow. It is laid called cavitation and occurs during winter and spring storms
What is abrasion
The waves pick up rocks and throw them against other rocks or cliff faces and it smooths the rock, like sandpaper. It happens all year round.
What is a shingle
Rounded rocks that are between 0.2 cm and 20cm
What is corrosion
Salt and chemicals in the water act to dissolve the rocks they touch, an example - limestone is dissolved by sea salt. Corrosion is also named solution and sea water is slightly alkali and happens in spring where sea water and air affect the rock
What is attrition
The sea picks up angular rocks and knocks them into each other. This chips away the corners to make it rounder and occurs in winter and spring during large storms
What is mass movement
The downhill movement of rock and soul under gravity
What is erosion
The breakdown and removal of rock along the coastline
What is transportation
Long shore drift (LSD) and movement of material along the coast
How are waves formed
The wind caused a wave as the water particles move in a regular circular formation. It breaks on the shore because the particles can’t move together
What affects wave height
Wind speed, wind duration and fetch
Why do small waves occur
If the wind speed is slow, the waves will also be small, regardless of the wind duration and fetch
Why do big waves occur
The stronger the wind, the larger the waves(wind speed). The longer the wind acts upon the waves, the larger they will be (wind duration). The longer the distance where waves can form (fetch)
What is wind duration
How long the wind blows for
What is fetch
The maximum distance which waves can form (between coasts) where the wind blows in one direction
What is swash
When water goes up the beach
What is backwash
When water goes down the beach
What are prevailing winds
The most frequent wind direction a place has (eg. UK’s prevailing wind is south west)
What is the largest fetch that goes to the UK
The fetch is up to 8000km from Brazil
What are constructive waves
Constructive waves have a long wave length and low wave height (low frequency), a strong swash but weak backwash and has a rolling break on the shore
What is the result of constructive waves having a strong swash
The wave pushes material up the beach (deposition)
Why do constructive waves have a weak backwash
Most energy is absorbed by friction
What are destructive waves
They have a high wave height and low wave length (high frequency), a crashing break on the shore which picks up rocks and shingle, a powerful swash and even stronger backwash
What is the result of destructive waves having a strong swash
It breaks apart the cliff face
What is the result of destructive waves having a strong backwash
It carries material away (erosion)
What are the horizontal lines called on a cliff face
Bedding planes
What are the vertical lines called on a cliff face
Joints planes
How do wave cut platforms occur
- Weathering weakens the cliff
- Base of cliff breaks off by destructive waves, resulting in a wave cut notch
- Abrasion wears away at the wave cut platform
- The wave cut platform (base) is eroded
- The undercutting of the cliff cause it to collapse
What is the intertidal zone
The area between the high tides and low tides
Where is the power from destructive waves generated
Gravity from the large wave height
What type of beaches are formed from destructive waves
Steep beaches
What type of beaches are formed by constructive waves
Flat beaches
How is it noticeable there is not a lot of mass movement
If there is vegetation, there is no to little mass movement otherwise it wouldn’t have enough time to grow
What are the types of mass movement
Rockfall, mudflow, landslide and rotational slip
What is rockfall mass movement
Bits of rock fall of the cliff face as scree, usually due to freeze thaw weathering, and it occurs on steep/ vertical cliffs.It is also fast
What is mudflow mass movement
Saturated soil (soil filled with water) flows down a slope. There is a lack of vegetation (roots) to hold it together. The lobe is a rounded extension of flowing mud that shows the direction of mass movement. It is also slow
What is scree
Loose rock that covers a mountain to cliff
What is landslide mass movement
Large blocks of rock slide downhill. The greater the angle (steep) it will go faster but the smaller the angle (flat) the slower the rocks will move.
What is rotational slip mass movement
Saturated soil falls down a curved surface and slides into the sea. It is also a slow process and has grass+ vegetation
How is it known rotational slip mass movement is a short process
It has vegetation
What are the four parts of rotational slip mass movement in order
Head, scarp, feet and toe
What is the head in rotational slip mass movement
The start of the landslide, usually the steepest
What is the scarp in rotational slip mass movement
It shows where it was eroded before the material slid down
What is the foot in rotational slip mass movement
The flat base of the slope that bulges out due to the collection of fallen materials
What is the toe in rotational slip mass movement
It collects all of the settled material or eventually can push it to the ocean
What are the 4 methods of transportation
Saltation, suspension, traction and solution
How do headlands and bays form and what are they
When there is hard and soft rock, the soft rock erodes quicker so the hard rocks sticks out while the soft rock is inwards. The part where the hard rock sticks out is called the headlands and when the bay is deeper inwards it’s called the bays
What is solution transportation
Minerals in rocks are dissolved by sea water
What is suspension transportation
Small particles suspended in the flow of water
What is saltation transportation
Small pieces of shingle are bounced along the seabed
What is traction transportation
Larger rocks are rolled along the sea bed
How does deposition occur
When the sea loses energy it drops the material it was carrying
How does differential erosion occur
When different rocks erode at different rates
What is another name for abrasion
Corrasian
What is long shore drift
- The waves hit the coast at an angle
- Swash carries sediment to the beach
- Backwash carries sediment down at right angles to the beach
- This creates a zig zag pattern
What is a sand dune
When wind brings sand further up the beach but objects can be in the way, such as sticks, can block the wind leading to hills of sand. This leads to build up of sand.
What are salt marshes
Coastal wetlands that are flooded by salt water
What is a tombolo
A stretch of sand that joins an island to a main island
Which rock is most resistant to erosion
Granite
What is the difference between transportation and long shore drift
Transportation is the movement of sediment but long shore drift is the movement of sediment along the coast
How are caves, arches, sea stacks and stumps formed
- Crack of weakness from hydraulic action on a headland
- Cracks widen by abrasion and hydraulic action so a cave forms
- If a cave forms on both sides, it forms an arch
- The base of the arch widens but the roof gets heavy and becomes unstable so it collapses leaving a stack
- The stack turns into a stump either by erosion so it topples over or weathering from the top of the stack until it becomes a stump
How are beaches made
Deposition
How are spits formed
- Longshore drift moves material along the coastline
- The coastline changes direction and material is deposited so a spit forms over time
- The spit grows and develops a hook if the wind direction changes
- Waves can’t get over a spit so silt is deposited and mud flats or salt marshes form
- The spit doesn’t form a sand bar because of the river current behind the river estuary
What is a bar
- There is a bay
- Long shore drift drags sand from the bay head beach
- A sand bar and lagoon is formed. There is a bar of sand and water (lagoon) is trapped behind
Example of an arch in a headland
Durdle Door in Dorset
What is a discordant coastline
Where there are different types of rock along a coastline so the coast erodes unevenly. The rock strata is 90 to the coastline.
What is a concordant coastline
Where there is the same type of rock along a coastline. The rock strata is parallel to the coastline.
Example of headland
Peveril point
Example of a bay
Swanage Bay
Layout of a question asking what process and why
- Process
- Conditions
- Cause
- Result
What is unconsolidated sediment
Loose rocks and this can be used to describe rotational slip and mudflow
What is a bay head beach
The sand underneath a bay
What is a river estuary
Where rivers meet the sea
