paper 1, section c, physical landscapes in the uk Flashcards
what is relief?
the physical features of the landscape (height above sea level, steepness of slopes and shape of landscape features)
what is relief determined mainly by?
geology (rocks)
e.g. granite and slate - dramatic mountain ranges (Arran in Scotland), clay and limestone - low-lying plains and gently rolling landscapes
what is the highest mountain in the UK?
Ben Nevis (1347m)
how do waves form?
- wind blowing over the sea
- friction with the surface = ripples = waves
what is fetch?
distance the wind blows across the water
- the longer the fetch, the more powerful the wave
what happens when waves reach the coast?
- in the open sea, despite wavy surface, there is little horizontal movement of water
- when waves approach shore there’s forward movement of water as waves break and surge up the beach
- the seabed interrupts the circular movement of the water
- as the water becomes shallower, the circular motion becomes more elliptical
- this makes the crest of the wave rise up and eventually collapse onto the beach
what is swash?
the water that rushes up the beach
what is backwash?
the water that flows back towards the sea
what are the 2 types of wave?
- constructive waves
- destructive waves
what are some characteristics of constructive waves?
- low waves
- surge up the beach and ‘spill’ with powerful swash
- carry and deposit large amounts of sand and pebbles = ‘construct’ beach = more extensive
- preferred by surfers = longer rides
- formed by storms 100s km away
what are some characteristics of destructive waves?
- formed by local storms - close to the coast
- can erode beach
- high wave frequency - often interfere with each other - chaotic mass of water
- high and steep = plunge onto beach
- little forward motion (swash) when it breaks but powerful backwash = removal of sand and pebbles = gradual destruction of the beach
wave height of constructive wave?
low
wave height of destructive wave?
high
wave length of constructive wave?
far/long
wave length of destructive wave?
short
type of wave (spilling or plunging); constructive wave?
spilling
type of wave (spilling or plunging); destructive wave?
plunging
strength of swash of constructive wave?
strong
strength of swash of destructive wave?
weak
strength of backwash of constructive wave?
weak
strength of backwash of destructive wave?
strong
net beach sediment (gain or loss) for constructive wave?
gain
net beach sediment (gain or loss) for destructive wave?
loss
what is weathering?
the weakening or decay of rocks in their original place on, or close to, the ground surface
what are the 3 types of weathering?
- mechanical (physical)
- chemical
- biological
what is mechanical/physical weathering?
the disintegration of rocks, often resulting in scree (pile of rocks) found at the foot of the cliff
what is chemical weathering?
caused by chemical changes; rainwater is slightly acidic which very slowly dissolves certain types of rocks and minerals
what is biological weathering?
due to actions of flora and fauna e.g. plants roots crack into the rocks, animals burrowing etc
what are some weathering processes?
- salt weathering
- carbonation
- freeze-thaw
describe salt weathering
mechanical
- when seawater evaporates it leaves behind salt crystals
- these grow and expand in cracks putting pressure on the rocks = flakes eventually break off
describe carbonation
chemical
- rainwater absorbs CO2 from the air, becoming slightly acidic
- contact with alkaline rocks creates chemical reactions = slowly dissolve e.g. limestone and chalk
describe freeze thaw
mechanical
- water collects in cracks in rock
- water freezes to form ice and causes stresses and cracks are enlarged
- after repeated freezing and thawing, rock fragment breaks off and collects as scree at the foot of the rock face
what is mass movement?
the shifting of rocks and loose material down slope under the influence of gravity
what are the coastal erosion processes?
- hydraulic power
- corrosion/solution
- attrition
- corrasion/abrasion
what is hydraulic power?
the power of the water
what is corrosion/solution?
the chemical breakdown of the rocks
what is attrition?
the wearing away of the rock material as they hit each other
what is corrasion/abrasion?
the sandpapering effect of the broken away material thrown back at the coast
what are the coastal transportation processes?
- suspension
- solution
- traction
- saltation
what is suspension?
fine material such as clay and sediment is carried by the sea
what is solution (transportation)?
dissolved minerals are carried by the sea
what is traction?
large boulders and pebbles are rolled along the sea bed
what is saltation?
small stones, pebble and silt bounces along the sea bed
what is longshore drift and how does it work?
- movement of sediment on the beach depends on the direction that the waves approach the coast
- if the approach is ‘head on’ sediment will move up and down
- if they approach at an angle = move along the beach in a zigzag pattern = longshore drift = beaches and spits
- the backwash carries the sediment back down the beach as the wave retreats to the sea
what is coastal deposition?
- it happens when there is lots of erosion elsewhere on the coast, meaning there’s lots of sediment available
- that sediment is then dropped in areas where the flow of the water slows down (loss of energy), usually where the coastline changes direction e.g. in sheltered bays: mudflats and salt marshes are often found in sheltered estuaries behind spits
what are some coastal erosion landforms?
- headlands and bays
- cliffs and wave-cut platforms
- caves, arches and stacks
information about headlands and bays
- common coastal landforms
- usually form where rocks of different strength are exposed
- weaker bands of clay are eroded more rapidly than the neighbouring bands of more resistant sandstone and limestone
- over time, the eroded clay forms bays where, under sheltered conditions, sediment is deposited to form beaches
- the more resistant rocks stick out into the sea to form headlands which are often battered by powerful waves to form steep cliffs
- deposition does not occur due to the lack of shelter at headlands (this explains the absence off beaches)
what are examples of headlands and bays?
Duriston Head
- limestone
- steep sides
- high energy area affected by destructive waves
- hard rock jutting out to sea
Swanage Bay
- crescent shaped
- soft roc such as sand and clay forming a crescent shape
- low energy constructive waves
- two headlands mark the edges of the bay
information about cliffs and wave-cut platforms
- when waves break against a cliff, erosion close to the high tide line will wear away the cliff to form a wave cut notch
- over a long period of time (hundreds of years) the notch will get deeper and deeper, undercutting the cliff
- eventually, the overlying cliff can no longer support its own weight and it collapses
- through continual sequence of wave-cut notch formation and cliff collapse, the cliff will gradually retreat
- in its place will be a gently sloping rocky platform called a wave-cut platform
- a wave-cut platform is typically quite smooth due to the process of abrasion
- however, in some places it may be scarred with rock pools
information about caves, arches and stacks
- starts with a joint or fault in resistant rock
- abrasion and hydraulic action widen the join to form a cave
- waves make the cave larger until it cuts through the headland to make an arch
- the arch is eroded and the roof becomes too heavy and collapses
- this leaves a tall stack
- the stack is eroded and collapses, leaving a stump
how do hard and soft rocks affect landforms?
- hard rocks such as granite, limestone and chalk are tougher and more resistant to erosion than soft rocks such as clays and sands
- the harder rocks form impressive cliffs and headlands that point out to sea, whilst soft rocks form bays or low-lying stretches of the coastline
what is a concordant coastline?
rocks are parallel to the wave front and therefore rates of erosion are similar along the coastline
what is a discordant coastline?
differential erosion may occur, where bands of hard and soft rock outcrop at right angles to the sea
what are some coastal depositional landforms?
- beaches
- sand dunes
- sand spits and bars
what are beaches?
deposits of sand and shingle (pebbles) at the coast:
- sandy beaches are mainly found in sheltered bays; the waves entering the bay are constructive waves, they have a strong swash and build up the beach
- some beaches aren’t made of sand; lots of the coast in the south of England have pebble beaches; these high energy environments wash away finer sand and leave larger pebbles (these come from nearby eroded cliffs or are deposited onshore from vast accumulations out to sea)
what are sand dunes?
accumulations of sand grains, shaped into mounds or ridges by the wind under the influence of gravity; they are found at the back of beaches above the maximum reach of the waves
how are sand dunes formed?
- embryo dunes form around deposited obstacles such as pieces of wood or rocks
- these develop and stabilised by vegetation to form fore dunes and tall yellow dunes; marram grass is adapted to the windy, exposed conditions and has long roots to find water, these roots help bind the sand together and stabilise the dunes
- in time, rotting vegetation adds organic matter to the sand making it more fertile; a much greater range of plants colonise these ‘back’ dunes
- wind can form depressions in the sand called dune slacks, in which ponds may form
what does a sand dune need to form?
- a large, flat beach
- a large supply of sand
- a large, tidal range, so there is time for the sand to dry
- an onshore wind to move sand to the back of the beach
- an obstacle such as drift wood for the dune to form against
how are spits formed?
- longshore drift transports sand along the coast
- the coastline changes direction and the waves begin to lose energy
- deposition starts to build up at the proximal end and the spit grows out into the sea
- the spit is exposed to changes in wind and wave direction which cause the distal end to hook back towards the land
how are bars formed?
- a spit may continue to grow across a bay due to LSD
- freshwater is trapped behind it to form a lagoon
- this feature is called a bar
what are the two types of engineering used for coastal management?
hard engineering and soft engineering
what is hard engineering?
- use of artificial structures to control natural processes
- options tend to be expensive, short-term
- they may also have a high impact on the landscape or the environment and be unsustainable
what is soft engineering?
- often much less expensive than hard engineering options
- usually more long-term and sustainable, with less impact on the environment
what are the hard engineering methods of coastal management?
- sea wall
- groynes
- rock armour
- gabions
what are the soft engineering methods of coastal management?
- beach nourishment/reprofiling
- dune regeneration
- dune fencing
what are sea walls?
- concrete or rock barrier against the sea, placed at the foot of cliffs or at the top of a beach
- has a curved face to reflect the waves back into the sea
- costs around £5,000-£10,000 per metre
advantages/disadvantages of sea walls?
advantages
- gives people a sense of security and often has a walkway
- if well maintained, they can be effective for many years by making the cost worthwhile
disadvantages
- very expensive and encounter high maintenance costs
- from the beach, a sea wall is ugly to look at
- sea walls may also destroy habitats
what are groynes?
- timber/rock structures built out to the sea from the coast that slow down and trap sediment moved by longshore drift to allow beaches to build up
- cost £150,000 every 200m
advantages/disadvantages of groynes?
advantages
- if well maintained, can last up to 40 years
- some groynes have concrete crests for people to walk along to reach a viewing or fishing point and also acting as windbreaks
disadvantages
- barriers which impede walking along a beach
- may be considered unattractive, especially old and degraded ones
what is rock armour?
- piles of large boulders placed at the base of the cliff, forcing waves to break, absorbing energy and protecting the cliffs
- costs around £200,000 per 100m
advantages/disadvantages of rock armour?
advantages
- piles of large boulders placed at the base of the cliff which protects the cliffs
- often used as a platform for fishing
disadvantages
- imported rocks do not blend in with the local geology
- rock armour is ugly and it often covers vast areas of a beach
- litter can become trapped in the structure
what are gabions?
- wire cages filled with rocks placed a the cliff based to provide support and to absorb wave energy
- costs £50,000 per 100m
advantages/disadvantages of gabions?
advantages
- for the cost, they are good value for money as may last 20-25 years
- can become visually appealing if vegetated and looked after
disadvantages
- may only last 5-10 years before rusting
- seabirds may damage their feet in them
what is beach nourishment/reprofiling?
- the addition of sediment to the beach to make it wider and higher
- the sediment is usually obtained offshore locally so it blends in with existing beach material
- bulldozers shape the material once on the beach (re-profiling)
- although cheaper than hard engineering options, has high overheads and costs around £500,000 per 100m
advantages/disadvantages of beach nourishment/reprofiling?
advantages
- a wider beach means more room for beach users, attracting more tourists
- people living along the sea front are more protected from coastal flooding
- at sandbanks, the wider nourished beach protects expensive properties
disadvantages
- it does require constant maintenance (unless there are other structures built to retain the beach)
what is dune regeneration?
- sand dunes are effective natural coastal defenders but due to trampling, they are easily damaged, becoming ineffective
- marram grass is planted to help stabilise the dunes and allow them to develop further
- fences are then created to deter people from crossing over the dunes
- cost £200-£2000 per 100m
advantages/disadvantages of dune regeneration?
advantages
- relatively cheap
- they maintain the natural environment that is popular with people and wildlife
disadvantages
- planting the marram grass and fencing off the areas can be time consuming and then can be damaged by storms
- people don’t always respond to the deterrent of the fenced off areas and continue to walk through
what is dune fencing?
- fences are constructed in front of the dunes along the seaward side (facing the sea) in order to encourage new dune formation
- these newly formed dunes help to protect the existing dunes
- they cost £400-£2000 per 100m
advantages/disadvantages of dune fencing?
advantages
- there is very minimal impact on the natural systems of the area
- they can control public access to protect other ecosystems
disadvantages
- can be somewhat unsightly, especially if they are broken
- require regular maintenance especially during stormy weather
what is managed retreat?
coastal management (a form of soft engineering)
- the deliberate policy of allowing the sea to flood or erode an area (often an area or low £ value)
what are some advantages of managed retreat?
- allow natural processes to take place = less intrusive than HE
- long-term = sustainable
- less expensive generally and with climate change, a quicker response (sustainable)
what is an example of managed retreat?
Medmerry Managed Retreat, near Chichester, West Sussex
- low-lying coastline- mainly used for farming and caravan parks
- previously protected by a low sea wall
- was in need of repair- would cost too much
- allowed the sea to breach current defences
- flood some farmland
Scheme: The Medmerry Scheme - £28 million
how is managed retreat sustainable/helping the future?
- creates a large salt marsh- natural buffer against the sea
- protection for the farmlands and caravan park
- encourage tourism- visitors to the area £££
- help establish a valuable wildlife habitat