Landform process and change Flashcards
Define fluvial
Referring to a river and it’s landforms
Define erosion
Wearing away of the land
Define transportation
Movement of material by the flow of water
Define deposition
Dropping of the material carried by the river
Define bed load
Material carried by the river being bounced or rolled along it’s bed
Define meander
Bend in the river formed by lateral (sideways) erosion
Define abrasion
stones and material carried by the river hitting the river bed and banks wearing them away
Define hydraulic action
Sheer force of water hitting the river bed and banks, compressing air in gaps in the soil and rock which causes material to be washed away
Define solution
Slightly acidic river water dissolves chalk and limestone rocks which are made from calcium carbonate
Name 3 erosional processes of the river channel
- Abrasion
- Hydraulic Action
- Solution
Name 2 erosional processes of the bed load
- Attrition
2. Abrasion
Define attrition
Stones carried by the river collide together and are broken down becoming rounder and smaller
Name 4 ways of transportation
- Solution
- Suspension
- Saltation
- Traction
Define suspension
Light material is held up and carried within the river’s flow - suspended load
Define saltation
Small pebbles and stones are bounced along the river bed. Load is alternately lifted then dropped in line with a local rise and fall in the velocity of the water
Define traction
Large boulders and rocks are rolled along the river bed. Load carried in this way is called bed load
When does a river deposit it’s material?
When the speed of flow is too slow for it to carry the load
Name 3 reasons why deposition may occur
- Lack of rainfall so less water moving in river channel
- Inside of a meander because majority of water is on the outside of bend meaning water on inside is moving slower and cannot transport it’s load
- Mouth of river where water flows against direction of the sea
Name 5 landforms shaped by fluvial processes
- V-shaped valleys
- Waterfalls
- Gorges
- Floodplains
- Meanders
Define V-Shaped valley
Narrow valley with steep sloping sides found in the river’s upper course
Define Waterfall
Water falling from a higher level to a lower level due to a change in rock structure or as a result of glacial erosion
Define gorge
Steep-sided narrow valley formed by a retreating waterfall
Define floodplain
Flat piece of land on either side of a river forming the valley floor
Define vertical erosion
Erosion of river channel that results in it’s deepening rather than widening
Define interlocking spurs
Hard, resistant rocks that a river cannot easily erode and therefore the river goes around them
Define plunge pool
A deepened part of the river bed at the base of the waterfall caused by the impact of the falling water
Name an example of a v-shaped valley
Brecon Beacons
Describe the v-shaped valley at Brecon Beacons (5)
- Vertical erosion and weathering create a V-shape in the supper course
- Weathering process such as freeze-thaw and biological weathering break down soil and rock on the valley sides
- Vertical erosion makes channel cut deeper into landscape leaved steep valley sides
- Weathered material is carried into river by gravity and washed away
- Stream has to go around interlocking spurs
Name 2 ways waterfalls can be formed
- Glacial erosion
2. Differential erosion
Describe how glacial erosion forms a waterfall (2)
- Glaciers carved deep valleys into landscape often hanging above one another
- Once glacier has melted, water drains from smaller valleys and falls into the larger ones
Describe how differential erosion causes a waterfall
- As river bed crosses onto soft rock from hard rock it is eroded (hydraulic action and abrasion) at a faster rate and a step is created
- As water falls, hydraulic action continues to erode the rock underneath the hard rock as it splashes against it
- Soft rock further eroded, overhang becomes too heavy and rock collapses, causing position of waterfall to retreat upstream
- Plunge pool created underneath waterfall due to force of the water hitting the river bed and abrasion caused by rocks from overhang being moved by the water
Define slip off slope
Bank of gently sloping deposited material found on the inside of the bend of a meander
Where are meanders usually formed?
Middle and lower course of a river
Define slope processes
Processes involved in moving material from the cliffs on to the beach
Define weathering
Breakdown of rocks in place by elements of the weather
Define freeze-thaw action
Breakdown of rocks due to water entering cracks and repeatedly freezing and thawing
Define carbonation
Where chemicals in rainwater such as carbonic acid react with chemicals in rocks such as limestone
Define mass movement
When soil, rocks or stones move down a slope
Describe evidence of erosion at Glamorgan Heritage Coast (3)
- Cliff parts loosened by weathering process
- Evidence of rockfall at the base of the cliff - angular rocks
- Waves hit base of cliff can cause a rockfall
Describe evidence of landslides at cliffs on Isle of Wight (2)
- Concave scar left on upper cliff with fan-shaped pile of debris at the base of the cliff
- As waves erode base of cliff, large section collapses
Name 3 processes that erode a cliff
- Hydraulic Action
- Abrasion
- Solution
Name 2 processes that erode beach material
- Abrasion
2. Attrition
Define sediment
Material carried by the sea
Define longshore drift
Process by which sediment is moved along the coastline
Name an example of sand dunes created by longshore drift
Ynyslas
Describe the general formation of a waterfall (6)
- A cap rock of sandstone is resistant - erodes relatively slowly
- Overhang susceptible to collapse and retreat
- Abrasion deepens the plunge pool
- Attrition breaks down the eroded rock fragments as they are transported downstream
- Pebbles swirl around in hollows to create potholes by abrasion
- Beds of resistant rock create an irregular river bed of rapids and smaller waterfalls below the waterfall
Describe the process of longshore drift (5)
- Waves approach at an angle
- Material is carried up a beach at an angle
- Material is picked up again and moves along
- Material carried straight down the beach as the water retreats
- A wood or concrete groyne built to stop material moving further along the beach
Describe the transport of sediment at Borth and Yyslas (2)
- Sediment swept on to the beach in the swash
2. Sand blown onshore and is deposited on the leeward side of the dunes
Define headland
Area of land that juts into the sea
Define Bay
Recessed area of coastline often found between two headlands
Define Wave-cut platform
Coastal landform made of a rocky shelf in front of a cliff
Define wave-cut notch
Slot with overhanging rocks that has been cut into the bottom of a cliff by wave action
Define bedding plane
Clearly seen layers of rock in a cliff face
Define arch
A natural opening in a cliff where the sea is able to flow through
Define stack
Vertical pillar of rock left behind after the collapse of an arch
Describe the formation of a wave-cut platform (4)
- Hydraulic action and abrasion cut a wave cut notch due to pounding of the sea , in the base of the cliff making it vulnerable to collapse
- With continual erosion the rock will get weaker and eventually collapse
- Material moved by the sea and abrasion will smooth the service of the wave-cut platform left behind
- If cliff made from well-joint sedimentary rocks then the wave-cut notch will occur along the bedding planes as these are a weak point and will erode much more quickly
Describe how an arch (and then stack) forms (5)
- When 2 caves are created either side of a headland
- Sea cuts through back wall overtime through abrasion and hydraulic action
- Once broken through and water can pass underneath the rock weathering will erode the roof of the arch so that it becomes higher and the roof thinner
- At the same time wave-cut notches form on base of arch to widen it meaning the arch roof becomes thinner
- Arch roof collapses and left with single pillar of rock called a stack
Define swash
Movement of water up the beach as a wave breaks
Define backswash
Flow of water back into the sea after a wave have broken on to the shore
Define beach
Created by deposition and lies between the high water mark and the low water mark
Define spit
A sand or shingle beach that is joined to the land but projects outwards into the sea in the direction of the prevailing wind
Define offshore bar
Area of deposition that is slightly off the coastline in the estuary of a river
Name an example of a spit
Spurn point on Holderness coastline at mouth of river Humber
Describe the formation of an offshore bar
Fine silts and sands that are transported by river are deposited at river mouth forming an offshore bar
Name an example of an offshore bar
Mouth of the Dyfi Estuary
Describe the formation of a spit at Spurn Point, Holderness coastline (6)
- Spurn point is a narrow spit on the east coast of UK which has formed across part of the Humber Estuary
- The spit is 4.8km long and as narrow as 46m in places
- Sand and shingle moved along Holderness coastline by longshore drift to the mouth of the Humber river
- Deposition occurs in more sheltered water and a spit develops
- As more sand is deposited colonising plants such as marram grass begin to grow which stabilises the spt further
- Longshore drift continues along spit increasing it’s length
Define rock pool
A pool of sea water between shoreline rocks
why do rock pools develop?
At high tides the pools are covered by the sea and at low tide some sea water remains in the hollow creating a rock pool
How are rock pools enlarged?
Process of abrasion at high tide as small rocks within the pool whirl around due to movement of waves and gradually increase the size of the hollow
Describe an example of a rock type (Bishopston River, South Gower)
- Source is on milestone grit and crosses onto the carboniferous limestone near the village of Kittle
- Joints mean limestone being easily eroded by solution, large caverns and sink holes appear which enable river to run underground
- River channel on the surface is dry for the majority of the time and far less erosion occurs in the surface river channel as a result of the infrequent channel flow
Name and describe an example of a concordant coastline
- North Coast of Llyn Peninsula
- Layers of different rock types run parallel to the coastline
- Metamorphic rock erodes at the same rate so coast has few headlands and bays
Name and describe an example of a discordant coastline
- Coastline between Trwyn Llanbedrog headland and Aberscotch bay
- Headland consists of more resistant igneous rock (erodes slowly) and neighbouring Aberscotch bay of less resistant mudstone and shale (erodes faster)
- Different erosion rates results in the formation of headlands and bays
Define cavern
Large underground cave which has been created due to enlargement of joints in carboniferous limestone
Define sinkhole
Hole in the ground caused by a collapse of the surface layer, often found in carboniferous limestone areas where caverns are present
Define concordant coastline
Rock are formed parallel to the sea so that erosion rates along the coastline are even
Define discordant coastline
Rocks are formed at right angles to the sea and se erosion rates vary along the coastline depending on the rock type
Define groynes
Low wall or barrier on a beach built at right angles to the sea to restrict longshore drift
Describe how climate will affect the rate of change of the coast (3)
- Prevailing winds affects the angle at which the waves break onto the coastline and therefore the direction of erosion and transportation
- Waves break onto beach at this angle pushing material up and across the beach
- Wind direction determines where depositional features form
Describe how climate will affect the rate of change of rivers (2)
- More water flowing in a river the higher the erosion rate will be
- Highest erosion rates in UK river found during winter months when there is more rainfall
Describe how the climate will affect the rate of change of extreme weather events (4)
- Storm changes appearance of a coastline overnight
- The worse the storm the stronger the destructive waves
- It’s also due to wind speed and fetch
- Most powerful and destructive waves in UK come from the South West due to large distance of open water that the Atlantic ocean provides increasing fetch of the waves
Describe an example if a winter storm causing coastal damage (West Wales and East Sussex Coastlines) (3)
- Spring 2014 storms caused severe erosion of south and west coastlines
- Aberdaron - 30cm land eroded from cliffs and at Birling gap 9msquared of cliff crumbled into the sea
- Stretch of coastline suffered 7 years worth of erosion in just 3 months due to numerous storms
Describe impact of human activity on both river and coastal landscapes
- Management of meanders in a built up area gabions - cages filled with rocks, which absorb the power of water or reinforced concrete banks which resist the force of the water
- Management of beaches - coastline left exposed to erosion as longshore drift moves beach material along coastline
- Human settlements close to the coast are vulnerable due to cliff collapse or flooding
Name and describe an example of intended human activity at the coast (St Bees Beach in Cumbria)
- South-westerly winds drive sediment in a north-easterly direction along north Cambrian coast leaving the village vulnerable
- Groynes were built to restrict the movement of sand and maintain the beach for important tourist trade and protect it from flooding and erosion
Describe an example of impact of unintended human activity (Criccieth Coastline) (6)
- South coast of Gwynedd
- Cliffs composed of easily eroded material called glacial till
- Beach affected by longshore drift which moves glacial till from west to east along coastline
- Groynes keep material on the beach so it attracts visitors and income they bring
- Beach also protects coastline by absorbing wave energy
- To east of groynes there’s an area of cliff that is very prone to collapse likely due to lack of beach material protecting it due to groynes to the west
