Unit 1 C Coastal Landscapes In The Uk Flashcards
What is mechanical weathering
The breakdown of rock without changing its chemical compositions
What is chemical weathering
The break down of rock by changing its chemical composition
How does freeze-thaw weathering break up rock
- happens when temperatures alternates above and below 0°c
- water gets into rock that has cracks
- when water freezes it expands,putting pressure on the rock
- when water thaws it contacts,releasing pressure on rock
- repeated freezing and thawing widens the crack and causes rock to break up
How do carbonation weathering break up rocks
- rainwater has co2 dissolved in it which makes weak carbonic acid
- carbonic acids reacts with rock containing calcium carbonate so that rocks are dissolved by rainwater
What are the 3 types of mass movement
- slides-material shifts in a straight line
- slumps-material shifts with a rotation
- rockfalls-material breaks up and falls down slope
What are the 3 processes of erosion by waves
- hydraulic action
- abrasion
- attrition
How do wave cut platforms form
- Wave erodes base of cliff which forms wave-cut notch which is enlarged as erosion continues
- rock above notch becomes unstable and eventually collapses
- collapsed material washed away and new wave-cut notch starts to form
- repeated collapsing results in cliff retreating
- a wave-cut platform is the platform left behind as the cliff retreats
How are are Headlands and bays formed
- where there are alternating bands of resistant and less resistant rock along coast
- less resistant rock is eroded quickly and this forms a bay- bays have a gentle slope
- the resistant rock is eroded more slowly and its left jutting out,forming a headland- headlands have steep sides
Formation of caves,arches and stacks
- waves crash into the headlands and enlarge the cracks—mainly by hydraulic action and abrasion
- repeated erosion and enlargement of cracks causes a cave to form
- continued erosion and enlargement deepens the cave until it breaks through the headland forming an arch
- erosion continues to wear away the rock supporting the arch until it eventually collapses
- this forms a stack—an isolated rock that’s separated from the headland
How does longshore drift transport material along the coast
- waves follow direction of the prevailing wind
- they usually hit the cost at an oblique angle
- the awash carries material up the beach in the same direction as the waves
- backwash then carries material down beach at right angles,back towards the sea
- over time material zigzags along the coast
What are the 4 processes of transportation
Traction—large particles like boulders are rolled along the sea bed by force of water
Saltation—pebble-sized particles are bounced along sea bed by force of water
Suspension—small particles like silt and clay are carried along in the water
Solution—soluble materials dissolve in water and are carried along
What is deposition and when does it occur
When material being carried by seawater is dropped on the coast. Occurs when water carrying sediment slows down so isn’t moving fast enough to carry so much sediment
When can the amount of material deposited be increased
- when there’s lots of erosion elsewhere on the coast so lots of material available
- when there’s lots of transportation of material into an area
Characteristics of sand beaches
- flat and wide
- sand particles are weak
- long, gently sloped
Characteristics of a shingle beach
- steep and narrow
- shingle particles are large
- steep slope
How do spits form
- spits form at sharp bends on the coastline
- longshore drift transports sand and shingle past the bend and deposits it in the sea
- strong winds and waves can curve end of spit
- sheltered area behind spit is protected from waves—material accumulates in this area and plants grow
- over time sheltered area can become a mud flat or salt marsh
How do bars form
- formed when a spit joins two headlands together
- bar cuts off the bay between the headlands from the sea
- a lagoon can form behind the bar
How do sand dunes form
- sand deposited by longshore drift is moved up the beach by wind
- obstacles cause wind speed to decrease do sand is deposited,this sand is colonised by plants and grasses vegetation stabilises the sand and encourages more sand to accumulate there forming small dunes called embryo dunes
- over time the oldest dunes migrate inland as newer embryo dunes are formed
Name a coastal area which has erosional and depositions landforms and
A) name one erosional landform
B)name one depositions landform
Dorset coast
A)Durdle Door-an arch
B)Chesil Beach-a tombolo(type of bar)
Describe the difference between hard and soft engineering
Hard engineering are man-made structures built to control the flow of the sea and reduce flooding and erosion whereas soft engineering are schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
What is a sea wall
Hard engineered: A wall made out of a hard material like concrete that reflects waves back to sea.
Benefits and costs of sea walls
B-prevents erosion of coast
B-acts as barrier to prevent flooding
C-creates strong backwash which erodes under the wall
C-very expensive to build and maintain
What are Gabions
Hard engineered: A wall of wire cages filled with rocks usually built at the foot of the cliff
What are the benefits and costs of gabions
B-absorb wave energy so reduce erosion
B-cheap and easy to build
C-ugly
C-wire cages can corrode over time
