distinctive landscapes Flashcards
Define landscape
* Landscapes are made up of all the visible features of an area of land.
Define a natural landscape
* A landscape with more physical features, such as mountains or forest, is described as a natural landscape.
Define a built landscape
* If a landscape has more visible human features, like a town or a city, it’s described as a built landscape.
What can the UK’s natural landscape be spilt into?
- The UK’s natural landscape can be split into upland. lowland and glaciated landscapes.
What gives landscapes distinctive characteristics?
* The geology, climate and land uses in these landscapes give them distinctive characteristics.
Describe upland areas
- Mostly found in the north and west of the UK
- Generally formed of harder rocks which resist erosion e.g. slate, granite and some limestones.
- Many are glaciated landscapes, e.g. Snowdonia.
- The gradient of the land is often steep.
- The climate tends to be cooler and wetter.
- The harsh climate and thin soils allow rough vegetation to thrive, and some upland areas are used for forestry.
- Land uses include sheep farming, quarrying and tourism
Describe lowland areas
- Mostly found in the south and east
- Generally formed from softer rocks, e.g. chalk, clay and some sandstones.
- The landscape is flatter with gently rolling hills.
- The climate tends to be warmer and drier.
- Vegetation grows easily in the more fertile soils and includes grassy meadows and deciduous forests
- Land uses include quarrying and tourism, as well as dairy and arable farming (growing crops).
- Most urban areas and industries (e.g. factories) are located in lowland areas.
Describe glaciated landscapes
- During the last glacial period, ice covered the UK roughly as far south as this line, so glaciated landscapes are mostly found in upland areas in the north-west of the UK.
- Ice is very powerful, so it was able to erode the landscape, carving out valleys. It also deposited lots of material as it melted.
- Landscapes formed by glacial meltwater and deposits extend south of this line.
Define mechanical weathering
- Mechanical weathering is the breakdown of rock without changing its chemical composition.
Name the main type of mechanical weathering that affects landscapes in the UK
- Freeze-thaw weathering.
Explain the process of freeze-thaw weathering
* It happens when the temperature alternates above and below 0 °C (the freezing point of water).
* Water gets into rock that has cracks, e.g. granite.
* When the water freezes it expands, which puts pressure on the rock.
* When the water thaws it contracts, which releases the pressure on the rock.
* Repeated freezing and thawing widens the cracks and causes the rock to break up.
Describe salt-weathering
- Salt weathering is a similar process to freeze-thaw weathering
- Caused by the build-up of salt crystals deposited in cracks by waves.
Define chemical weathering
- Chemical weathering is the breakdown of rock by changing its chemical composition
What is carbonation weathering?
- Carbonation weathering is a type of chemical weathering that happens in warm and wet conditions
Explain the process of carbonation weathering
* Rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid.
* Carbonic acid reacts with rock that contains calcium carbonate,
e.g. carboniferous limestone, so the rocks are dissolved by the rainwater.
Define biological weathering
- Biological weathering is the breakdown of rocks by living things
Define mass movement
- Mass movement is the shifting of rocks and loose material down a slope, e.g. a cliff or valley side.
What causes mass movement to occur?
- It happens when the force of gravity acting on a slope is greater than the force supporting it.
What does mass movement cause?
* Mass movements cause coasts to retreat rapidly
What will increase the chances of mass movement happening?
- They’re more likely to happen when the material is full of water - it acts as a lubricant, and makes the material heavier.
- Undercutting of a slope by erosion will increase the chance of mass movement.
Name the two types of mass movement
- Rotational slumping
- Rockfall (slides)
Explain the process of rotational slumping
- Material shifts with a rotation
Explain the process of rockfall (slides)
- Material shifts in a straight line
Name the four processes of erosion
- The same four processes of erosion occur along coasts and in river channels
- Hydraulic action
- Abrasion
- Attrition
- Solution
Explain the process of hydraulic action
- Along coasts waves crash against rock and compress the air in the cracks.
- This puts pressure on the rock. Repeated compression widens the cracks and makes bits of rock break off.
- In rivers, the force of the water breaks rock particles away from the river channel.
Explain the process of abrasion
- Eroded particles in the water scrape and rub against rock in the sea bed, cliffs or river channel, removing small pieces and wearing them away.
- Most erosion in rivers happens by abrasion.
Explain the process of attrition
- Eroded particles in the water smash into each other and break into smaller fragments.
- Their edges also get rounded off as they rub together.
- The further material travels, the more eroded it gets.
E.g. attrition causes particle size to decrease between a river’s source and its mouth.
Explain the process of solution
- Dissolved carbon dioxide makes river and sea water slightly acidic.
- The acid reacts chemically with some rocks e.g. chalk and limestone, dissolving them.
How is eroded material transported?
- Eroded material is moved by rivers and the sea.
Define transportation
- The movement of eroded material
Name the four processes of transportation
- Traction
- Saltation
- Suspension
- Solution
Describe traction
- Large particles like boulders are pushed along the river bed or sea floor by the force of the water.
Describe saltation
- Pebble-sized particles are bounced along the river bed or sea floor by the force of the water.
Describe suspension
- Small particles like silt and clay are carried along by the water.
Describe solution
- Soluble materials dissolve in the water and are carried along
Define deposition
- Deposition is when material being carried by sea water or a river is dropped.
When does deposition occur?
- It occurs when water carrying sediment loses velocity (slows down) so that it isn’t moving fast enough to carry so much sediment.
Define constructive waves
- Waves that deposit more material than they erode are called constructive waves.
Describe constructive waves
- Constructive waves have a low frequency (6-8 waves per minute).
- They’re low and long.
Explain the process of coastal deposition
- The swash is powerful and it carries material up the coast.
- The backwash is weaker and it doesn’t take a lot of material back down the coast.
- This means there’s lots of deposition and very little erosion.
Define swash
- The movement of the water up the beach
Define backwash
- The movement of water down the beach
- Always perpendicular to the beach
When does the amount of material that is deposited on an area of coast increase?
- When there’s lots of erosion elsewhere on the coast, so there’s lots of material available.
- When there’s lots of transportation of material into the area.
When do rivers slow down and deposit material?
- Deposition in rivers occurs when:
- The volume of water in the river falls.
- The amount of eroded material in the water increases.
- The water is shallower, e.g. on the inside of a bend.
- The river reaches the sea or a lake at its mouth.
When do headlands / bays form?
- Headlands and bays form where there are alternating bands of resistant and less resistant rock along a coast.
Explain how headland bays form
- The less resistant rock (e.g. clay) is eroded quickly and this forms a bay - bays have a gentle slope.
- The resistant rock (e.g, chalk) is eroded more slowly and it’s left jutting out, forming a headland - headlands have steep sides.
Explain the process of headland erosion
- Headlands are usually made of resistant rocks that have weaknesses like cracks.
- Waves crash into the headlands and enlarge the cracks mainly by hydraulic power and abrasion.
- Repeated erosion and enlargement of the cracks causes a cave to form
- Continued erosion deepens the cave until it breaks through the headland - forming an arch, e.g. Durdle Door in Dorset.
- Erosion continues to wear away the rock supporting the arch, until it eventually collapses.
- This forms a stack - an isolated rock that’s separate from the headland, e.g. Old Harry in Dorset
Where are beaches found?
- Beaches are found on coasts between the high water mark and the low water mark
Define high water mark
- The highest point on the land the sea level gets to
Define low water mark
- The lowest point on the land the sea level gets to
How are beaches formed?
- They’re formed by constructive waves depositing material like sand and shingle.
Describe the characteristics of a sand beach
- Sand beaches are flat and wide
- Sand particles are small and the weak backwash can move them back down the beach, creating a long, gentle slope.
Describe the characteristics of a shingle beach
- Shingle beaches are steep and narrow
- Shingle particles are large and the weak backwash can’t move them back down the beach.
- The shingle particles build up and create a steep slope.
Define a spit
- Spits are just beaches that stick out into the sea - they’re joined to the coast at one end.
Spits form at sharp bends in the coastline, e.g. at a river mouth.
How are spits formed?
* Spits are formed by longshore drift
Define longshore drift
- A process that moves material along coasts
Explain the process of longshore drift
- Waves follow the direction of the prevailing (most common) wind.
- They usually hit the coast at an oblique angle (any angle that isn’t a right angle).
- The swash carries material up the beach, in the same direction as the waves.
- The backwash then carries material down the beach at tight angles, back towards the sea.
- Over time, material zigzags along the coast.
- Longshore drift transports sand and shingle past the bend and deposits it in the sea.
- Strong winds and waves can curve the end of the spit (forming a recurved end).
- The sheltered area behind the spit is protected from waves - lots of material accumulates in this area, which means plants can grow there.
- Over time, the sheltered area can become a mud flat or a salt marsh.
What is a river basin?
- A river basin is the area of land surrounding a river, where any rain falling on the land eventually makes its way into that river.
- This area is also called the river’s catchment.
What are river basins separated by?
- River basins are separated by a boundary called a watershed.
What is a watershed?
- They’re ridges of high land - water falling either side of these ridges will go into different river basins
Name some key features of a river basin
- A tributary is a smaller river (e.g. a stream) that joins a main river.
- The source is where a river starts, usually in an upland area (e.g, mountains)
- The mouth is where a river flows into the sea or a lake.
What is the downhill path of a river called?
- The path of a river as it flows downhill is called its course.
Name the three courses a river has
- Rivers have an upper course (closest to the source of the river), a middle course and a lower course (closest to the mouth of the river).
What do rivers form as they flow downhill?
- Rivers form channels and valleys as they flow downhill
How do rivers form channels and valleys?
* They erode the landscape - wear it down, then transport the material to somewhere else where it’s deposited
How does the shape of the valley and channel change along the river?
- The shape of the valley and channel changes along the river depending on whether erosion or deposition is the dominant process
Explain how V-shaped valleys are formed
- In the upper course of a river, fast-flowing water following heavy rain and high turbulence causes loose rough particles and boulders to be transported by the river and scraped along the river bed.
- This causes downwards erosion of the river channel by the process of abrasion.
- The valley sides are exposed to weathering (e.g. by freeze-thaw.
- The weathered material that falls down the valley sides into the river channel causes further erosion by abrasion.
- The river doesn’t have enough energy to erode sideways (laterally), so vertical erosion of the river bed is dominant, which deepens the river valley, creating a steep-sided V-shape.
Explain how waterfalls and gorges form
- Waterfalls form where a river flows over an area of hard rock followed by an area of softer rock
- The softer rock is eroded (by hydraulic action and abrasion) more than the hard rock, creating a ‘step’ in the river.
- As water goes over the step it erodes more and more of the softer rock.
- A steep drop is eventually created, which is called a waterfall.
- The hard rock is eventually undercut by erosion. It becomes unsupported and collapses.
- The collapsed rocks are swirled around at the foot of the waterfall where they erode the softer rock by abrasion
- This creates a deep plunge pool.
- Over time, more undercutting
causes more collapses. The waterfall will retreat (move back up the channel), leaving behind a steep-sided gorge.
When do river develop meanders?
- River develop large bends called meanders in their middle and lower courses, in areas where there are both shallow and deep sections in the channel
What type of erosion takes place on the outside bend of a river?
- Abrasion and hydraulic action
Explain how river cliffs are formed
* The current (the flow of the water) is faster on the outside of the bend because the river channel is deeper (there’s less friction to slow the water down).
* So more erosion takes place on the outside of the bend, forming river cliffs
Explain how slip-off slopes are formed
* The current is slower on the inside of the bend because the river channel is shallower (there’s more friction to slow the water down).
* So eroded material is deposited on the inside of the bend, forming slip-off slopes.
Explain how ox-bow lakes are formed
- Meanders get larger over time - they can eventually turn into an ox-bow lake
- Erosion causes the outside bends to get closer until there’s only a small bit of land left between the bends (called the neck)
- The river breaks through this land, usually during a flood and the river flows along the shortest course
- Deposition eventually cuts off the meander forming an ox-bow lake
What is a floodplain?
- The floodplain is the wide valley floor on either side of a river which occasionally gets flooded
Explain how a flood plain builds up
- When a river floods onto the floodplain, the water slows down and deposits the eroded material that it’s transporting.
- This builds up the floodplain (makes it higher).
- Meanders migrate (move) across the floodplain, making it wider.
- Meanders also migrate downstream, flattening out the valley floor.
- The deposition that happens on the slip-off slopes of meanders also builds up the floodplain.
Where are floodplains found?
- Lower course of a river
What are levees?
- Levees are natural embankments (raised bits) along the edges of a river channel.
Explain how levees are formed
* During a flood, eroded material is deposited over the whole floodplain.
* The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down.
* Over time, the deposited material builds up, creating levees along the edges of the channel, e.g. along the Yellow River (Huang He River) in China.
Where are levees found?
- Lower course of a river
