River Landscape Flashcards
What are the 3 weathering processes
Mechanical
Chemical
Biological
Describe how mechanical weathering works
- Water fills a crack or joint in the rock
- Water freezes and the crack is widened
- Repeated freeze-thaw action increases the size of the crack until the block of rock breaks off
- Loose blocks of rock are called scree
Describe how chemical weathering works
Rainwater is slightly acidic. The acid reacts with minerals in the rocks and dissolves them.
Describe how biological weathering works
Roots grow into cracks and split rocks apart
Define sliding
Where rock, weathered or eroded material or Earth moves down a slope. Gravity pulls the weakened material quickly downwards
Define slumping
Where the river erodes the bottom of the valley slope, making it steeper. Material above slides downwards, particularly if it is saturated with rainwater
What is the point where two rivers meet called
Confluence
The _ is an imaginary line that separates on drainage basin from the next
Watershed
What is a flood plan
The land that may get flooded when a river flows
What are tributaries
Smaller rivers join the main one
What is a channel
Where the river flows
What is a mouth of the river
This is were it flows into a lake or the sun, or the ocean
What is drainage basin
The river is fed by the rain that falls in the area inside the red dished line
Define source
The starting point of the river
Define weathering
The breakdown and decay of rock by natural processes
What are the three types of weathering
Physical
Chemical
Mechanical
What is Freeze Thaw Action
This happens when rainwater enters cracks or gaps in the rock and then freeze if the temperature drop below zero degrees. The water expands and turns into ice and experts pressure on the rock, causing it to break into smaller pieces
Define scree
Loose pieces if rock with sharp edges. They are broken off by Freeze Thaw Action, roll down the mountainside
What is biological weathering
Roots if a plant, especially trees, can growing creates in a rock and split them apart
What is mass movement
Movement of rocks and soil downslope due to gravity, helped by weaker rocks, steep slopes and heavy rotation
Define soil creep
Individual particles of soil more slowly down a slope
Define flows
Masses of soil or rock usually mixed with water flow like liquid downhill
What is sliding and slumping
Material moves radially down a slope in one go (landslide). In a slump material often rotates it moves
Define hydraulic action
In a fast-flowing river, water is forced into cracks on time it break them up
Define solution
Water also dissolves soluble minerals from the bed and banks. This helps to break them up
Define discharge
Is the volume of water flowing through the river
Define velocity
The speed at which a river flows
How is an Oxbow Lake formed
○ Erosion makes the neck narrow
○During floods river takes shortest course through the neck
○ There is a new straighter river course
How are Interlocking formed
As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.
How is a V-shaped Valley formed
○ The river cut down and deepens its valley
○ The river widens its valley as it deepens it
○ The river continues to widen its valley
How are waterfall and gorges formed
The soft rock is eroded quicker than the hard rock and this creates a step.
As erosion continues, the hard rock is undercut forming an overhang.
Abrasion and hydraulic action erode to create a plunge pool.
Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
This process continues and the waterfall retreats upstream.
A steep-sided valley is left where the waterfall once was. This is called a gorge.
How is a meander formed
As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
What type of rock is granite
Igneous
What type of rock is chalk
sedimentry
Explain why the lowland areas of the UK are mostly formed of sedimentary rocks
Sedimentary rocks, such as chalk, are relatively soft and are not made up of crystals. Therefore these are more easily broken down by weathering and erosion than igneous and metamorphic rocks. This results in Sedimentary rock forming the low hills and lowland basins south of the Tees-Exe line
Suggest how the Giant’s Causeway has polygon shaped rocks
Diverging plate boundaries about 60 million years ago meant that the Atlantic Ocean began to form. Rising lava cooled and contracted to form polygonal basalt shapes
State one way that agriculture had affected the UK landscape
Straight drainage ditches constructed
Explain one change to the landscape caused by forestry
Forestry can involve planting trees in straight lines. This changes the appearance of landscape because natural woodland forms irregular patterns
Explain why farming has produced different landscapes in upland and lowland UK
There are different types of farming in the UK’s upland landscapes. Steep slopes and poor soils in upland areas mean that these are used for rough grazing. Lowland landscapes may have straight drainage ditches and large, regular shaped fields
Suggest one way settlements such as Shrewsbury create a distinctive landscape
Building settlements such as Shrewsbury means that the natural landscape. House other buildings are tightly packed together along roads in the centre of the meander loop
Identify the process by which rocks are broken down in situ
Weathering
Explain two ways that a coastline can be eroded by wave action
One way the coastline is eroded by abrasion, which takes place when breaking waves throw sand, pebbles and boulders against the coast during storm, causing rocks to be broken down and removed. Another type of coastal erosion is hydraulic action, where the weight and energy of waves, particularly during a storm, erode the coast. As part of the process, waves compress air in joints in rocs, forcing them apart
Explain how waves transport material
The largest material, such as boulders, is rolled along the seabed by traction. Smaller pebbles are bounced along the seabed by saltation
Explain the process of deposition of material (load) transported by waves
The load transported by a wave is deposited when a wave loses energy
Suggest how the landforms vary between a coastline made up of hard rocks and a coastline made up of soft rocks
A coastline made up of hard rocks will have cliffs that are high, steep and rugged, and landforms such as wave-cut platforms. However, a coastline made up of soft rocks will be less rugged and steep and have bays
State two differences between destructive ad constructive waves
Destructive waves are high-energy waves that cause coastal erosion. However, constructive waves are low-energy waves that cause coastal deposition
Prevailing winds affect the UK. Identify the direction from which theses prevailing winds come
South-east
Identify the type of weather prevailing winds bring to the UK
Warm, moist air and frequent rainfall
Identify the UK’s climate type
Temperate maritime
State one type of weathering that affects rocks along the coastline
Freeze-thaw weathering
Define the term coastal erosion
The breaking down and removal of material along the coast
Suggest two impacts of coastal erosion on the UK coastline
Coastal erosion can cause coastal recession, which is when the coastline moves inland. Frequent storms cause erosion and damage coastal landforms like spits
Explain the formation of a wave cut platform
- The cliff face and top are exposed to sub-aerial and weathering. This may include physical, chemical and biological weathering. This makes the cliff more susceptible to erosion
- The action of the sea causes erosion - mostly abrasion and attrition. This weakens the cliff base and helps with the cliff collapse
- The upper part of the cliff (over the wave cut notch) is no longer supported and will collapse into the sea
- Backwash removes the collapsed cliff face and this forms a wave cut platform
- The process repeats and the cliff retreats, which increase the size of the wave cut platform
Describe how an arch is formed in a coastal headland
A cave is formed when waves erode weaknesses in a headland such as joints. Over time processes such as abrasion cause the back of the cave to be eroded away to leave an arch in the headland
State two features of a bar
A bar is a long ridge made up of coastal sediment such as pebbles. A bar stretches across a bay, so that a section of seawater is cut off and dammed to from a lagoon
Explain why beaches can be formed of different sediment types
The type of sediment depends on the local geology. Due to erosion, nearby cliffs are eroded, or sediment is deposited by constructive waves. The shape of a beach profile varies. Low energy constructive waves produce a low-angle profile
Explain the formation of a spit
- Spits form when there is a change in direction of the coast
- Prevailing winds mean waves lose energy as they reach the coast
- Sediment is transported by longshore drift and deposited to form a spit
- The spit may be curved because there may be more than one LSD direction
Explain one way coastal recession might affect local people
The loss of people’s homes and disruption communication networks, such as roads and railway lines.
Suggest how the cliff-top settlement might affect the rate of erosion
Weight of buildings makes cliffs more vulnerable to mass movement. Buildings can increase water going into the soil, making it more saturated and increasing mass movement
Explain one way in which industry can change the coastal environment
Industry can increase air, noise and visual pollution. Visual pollution caused by large factories such as steelworks will have a major impact on the coastal environment. However, industry can bring wealth and jobs to coastal area and increase of awareness and investments in protecting coastal landscapes
Explain how coastal recession and flooding can affect the environment
Coastal recession and flooding can destroy wildlife habitats such as sand dune environments. Sand dunes are a natural form of coastal protection but are easily eroded by destructive waves. Increased deposition further along the coast will also affect the environment as spits may form, creating new landforms and habitats such as salt marshes
Define the term weathering
The breaking down of rocks in situ
Explain the process of mass movement that occurs in the upper courses if rivers
The upper sections of the river valley are affected by weathering processes such as freeze-thaw action. This will produce loosened rock boulders over time. This weathered and eroded material down the valley sides by mass movement, especially sliding when the loosened material moves down rapidly due to gravity
Define the term transport
Transport is the way in which the river carries eroded material or load
Define the term river long profile
How a river’s gradient changes between its source and its mouth
Explain how a river’s channel shape changes downstream
In the upper course, the river channels is narrow with steep sides.
In the middle course, the channel becomes wider and the sides become less steep.
In the lower course the channel becomes wider, has a flat bed and the sides become less steep
Explain two ways that river landscape contrast between the upper and lower sections of the long profile
The landscape of the up section of a river is formed by erosion, therefore landforms include waterfalls and interlocking spurs. However, the lower section of a river valley is formed by mainly depositional processes although some erosion is also involved to produce landforms such as flood plains and river meanders
For a named UK river you have studied, explain how local geology affects its long profile
The River Holford flows across a series of different sedimentary ricks. Its source is on the Quantock Hill where the resistant sandstone means that the river erodes vertically to form steep-sided valleys and a steep upper course profile. In the middle section, the Holford flows across softer clays which can be eroded laterally to produce a wide flood plain with a gently dipping long profile. At Kilve, where the river flows into the sea, it flows across limestone which has been eroded by past glacial events, giving a gentle profile.
Explain how extreme weather events can increase the risk of river flooding
Increasingly frequent storms cause rivers to exceed bank full conditions and flood. More frequent hot, dry weather makes topsoil impermeable, causing rapid surface run-off and a sudden increase in discharge, resulting in flooding
Explain how interlocking spurs form
In its upper course, the river erodes vertically. The fastest water flow in the river channel will also naturally swing from side to side, causing maximum erosion on the outside of each bend. This will result in lateral as well as vertical erosion, especially if the local geology has lines of weakness such as joints. Over time, a series of spurs are formed, which are ridges of upland sloping down to the stream on either side of the valley
Explain the formation of a gorge
Gorges are formed when erosional processes such as abrasion and hydraulic action cause a waterfall to retreat. The processes of undercutting and collapse are repeated over a long period of time, and the waterfall retreats, forming a steep-sided gorge
Explain the formation of a waterfall
Waterfalls occur where rocks of different hardness, and therefore resistance to erosion, occur together. The harder rock overlies the softer rock. The softer rock is eroded by hydraulic action and abrasion, undercutting the cap rock above. Over time, the cap rock collapses due to gravity. The height of the waterfall is increased with the formation of a plunge pool caused by hydraulic action and by fragments of cap rock and high-energy currents resulting in abrasion
Explain the formation of floodplains
Floodplains are formed by meanders eroding laterally as they travel downstream. Sediment is deposited on the opposite bank to form a point bar. The width of the floodplain is therefore determined by the amount of meander migration that occurs. When the river exceeds bank full and floods, it deposits layers of alluvium. These build up gradually over time to create the layers of sediment found on the floodplain
Identify the direction of erosion in the mid and lower sections of a river’s course
Lateral
State two changes to river channels that occur in the mid course
Width and depth increase
Examine how erosion and deposition work together in the formation of an oxbow lake (8)
When a river flows across its floodplain, it meanders. Deposition occurs on the inside of each bend where the current velocity is slower. At the same time, lateral erosion and undercutting occur on the outside of each meander where the velocity is higher. Continues deposition and erosion working together cause the formation of a pronounced meander with two outside banks becoming closer together. The narrow neck of land between the two meanders is finally eroded, either by lateral erosion or by the strong current during flooding. A new, straighter river channel is formed and the abandoned meander loop forms a cut-off. Continued deposition seal off the cut-off from the river channel to an ox-bow lake.
Explain one way that agriculture can affect river processes
Ploughing up and down a slop means that loose soil is transported into a river channel and can increase the amount of sediment deposited
Explain how human activities can affect the frequency of flood events
Urbanisation means that there are fewer permeable surfaces. Water flows into the river increasing discharge and therefore the risk of flooding. Field drains move water rapidly into streams and rivers, also increasing discharge and flood risk. Ploughing field up and down a slope can increase the amount of sediment in rivers, reducing channel capacity and increasing the flood risk
State one physical factor that can increase the risk of flooding
Sudden snowmelt
Examine how the interaction of physical and human processes worked together to form a named, distinctive river landscape ( 8 marks)
The source of the River Dee is Ddualt, Snowdonia, a glaciated upland area consisting of metamorphic and igneous rocks. Precipitation exceeds 3000 mm per annum, so the Dee erodes vertically to create a steep-sided valley in its upper course. Near Bala, the river is controlled by the Dee regulation Scheme, which means that human processes become more significant than physical processes in the river landscape. Reservoirs such as Lake Bala and Llyn Celyn prevent erosion in this part of the upper course, so erosion is replaced by deposition. The river is less regulated north of Chester and Meanders across a distinctive wide floodplain formed by erosion and deposition. The channelised section to the west of Chester prevents erosion and deposition, forming a man-made landscape. As the Dee flows into its estuary, its velocity decreases and deposition of sediment transported along channelised section causes extensive mudflats to form. The landscape of the Dee therefore varies depending on weather physical or human processes are more dominant
