Coastal Zone Knowledge Flashcards
What three factors effect the size of waves
The winds strength
How long the wind blows for
The length of the water the wind blows over (fetch)
What causes a wave to break
The friction between the water and the beach
Name the two different types of wave
Destructive
Constructive
Which way does the backwash go
Away from the beach
Which way does the swash go
Up the beach
Give four features if a destructive wave
High (in proportion to length)
Backwash is stronger
Frequent waves
Erosion occurs more
Give four features of a constructive waves
Low
Deposition occurs more than erosion
Swash is more powerful than the backwash
Less frequent waves
Name the three types of weathering
Mechanical
Chemical
Biological
Describe the freeze thaw process
Water gets into rocks through pores
The water freezes and expands by 9%
The expansion splits up the rock
Describe exfoliation
Large temperatures differences cause the rocks to expand and contract which leads to the top layer flaking off
Why does the rain cause chemical weathering
Rocks made up of calcium carbonate is rained on by rain that is naturally slightly acidic dissolves then
What causes waves
The friction between the wind and water
Describe biological weathering
Plants roots and animal burrows breaking away the cliff
Define mass movement
The downhill movement of sediment under the influence of gravity
Describe hydraulic action in a costal environment
The waves force water into cracks causing air pockets to compress thus making the cracks break open
Describe abrasion in a costal context
Loose rocks and stones are hurled against the cliff
How does longshore drift occur
Swash brings sediment up at an angle
Back swash brings it back down at 90 degrees due to gravity
Overall there is movement one way
Why is more sediment depositoed in bays
Because the wave energy is much less in bays
What is the name for bands of soft or hard rock
Strata
Which two ways can strata be arranged
Concordantly or disconcordantly
Bays and headlines are more likely to from at which type of coast
Disconcordant
What is a better name for a “bite” out of a cliff
A notch
Why do cliffs collapse
Erosion creates a notch once this becomes to big the cliff collapses
What does cliff retreat form
A wave cut platform
Why are wave cut platforms most often very smooth
Because of abrasion
Can headland erode
Yes
Describe the formation of an arch
Hydraulic action widens points of weakness in the cliff to form small caves. More erosion still increases the size of the cave until it becomes an arch
Describe how an arch can turn into a stump
Overtime more erosion takes place on the arch until it collapses. Forming a stack. The stack is undercut by erosion until it to collapses leaving just a bit if rock above water called a stump
What is a beach
An accumulation of sand or shingle
What process causes beaches to be formed paticularly in bays
Wave refraction
What is a spit
A bank of sand that is off the coastline which has been out there by longshore drift
What forms begins a spit
Mudflats
What makes a spit more likely to stay
Plants colonising it as the roots bind the sand
What forms behind a bar
A freshwater lake or lagoon
What is the biggest cause of rising sea levels
Thermal expansion
Other than thermal expansion what are two other reasons why sea levels rise
Isostatic change
Melting ice caps
Name two small islands that are at risk from sea level rising
Maldives and Tuvalu
Name 3 causes of costal flooding and increased costal erosion
Tides (spring tides)
Storm surges
Waves
What three things cause cliff collapse
Weathering
Erosion
Mass movement
What creates a storm surge
An area of low pressure such as a cyclone
What is meant by spring tide
A tide that rises greater than usual because the sun and moon are in alignment and so the gravitational force is greater
What role does erosion have to play in cliff collapse and which types do it
Hydraulic action and abrasion erode the bass if the cliff
What process erodes the top of a cliff
Weathering eg chemical
Describe why when the top layer of rock is saturated it can lead to costal erosion
The cliff has gained weight making it more likely to collapse, furthermore more water will run off the cliff and run off the face
How do humans increase the chances of cliff collapse
By building
Describe four methods used to prevent cliff collapse
Flatten the slopes to prevent mass movement
Inserting drainage
Place rock armour at the base
Putting Geotextiles (which allow water out) on the cliff
How much do sea walls cost per km
About £6 million
What are the pros of sea walls
Effective and used as a promenade
What are the negatives of sea walls
Expansive
Unnatural
What specific negatives do groynes have
They interrupt longshore drift and are very ugly
What is the cost of groynes and rock armour
Groynes £10,000 each (200m intervals)
Rock armour £1000-£4000 per meter
What common advantages do rock armour and groynes have
Fishing, effective
How do groynes work
They trap sand and increase the size of the beach meaning more energy is dissipated
Where is rock armour often placed
At the foot of the cliff
How does beach nourishment work
By adding sand and shingle on to the beach
How does dune regeneration work
Martha’s grass is planted to build or stabilise dunes which act as a barrier to the water
How does Marsh creation work
Allowing coastal areas to become salt marches which are effective costal barriers
What are the problems with marsh creation or managed retreat
Loses land meaning that the owners must be compensated
Name the four types of dune in order moving from the sea outwards
Embryo dunes
Fore dunes
Main ridge/ yellow dunes
Older dunes / grey dunes
What plants may you find on an embryo dune
Sea couch grass
Which two types of dune does marram grass grow most commonly
Fire dunes and main ridge
What plants may be found on the oldest dunes
Dune Heath, buckthorn
Describe as many conditions in which a dune is likely to form
Exposed between tides Prevailing onshore wind Fine sand Arid Salt spray Alkaline conditions
