P1 SC UK Physical Landscapes Flashcards
What is relief?
Relief describes the physical features of the landscape. Includes:
Height above sea level
Steepness of slopes
Shape of landforms
To the north and west are the ___ of England, Wales and Scotland
More ___ rocks such as ___ are found here
Uplands
Resistant
Granite and slate
South and east are the ___ of central and southern England
___ rocks such as ___ form low-lying ___ and rolling landscapes
Lowlands
Weaker
Clay and limestone
Plains
Landscapes result from…
The interaction between natural and physical factors
Most rivers have their source in…
Mountains or hills
The River Severn has its source in ___, is joined by the River ___ and flows into ___
The Cambrian Mountains, Wales
Avon
The Bristol Channel
How do waves form?
Wind blowing over the sea
Friction w surface of water causes ripples that develop into waves
What is the fetch?
Distance that wave-generating winds blow across the water
The longer the fetch…
The bigger the wave
What happens when waves reach the coast?
Circular orbit in open water
Friction with seabed distorts circular motion
Increasingly elliptical orbit as water is shallower, crest of wave moves faster
Wave breaks and collapses onto beach
Water returning to the sea is called…
Backwash
Water rushing up the beach is called…
Swash
What are the two types of wave
Constructive
Destructive
Constructive waves are formed by…
Storms hundreds of km away
Constructive waves are common at what time of year?
Summer
What are characteristics of constructive waves?
Low waves, crests far apart
Gently sloping wave front
Gently sloping beach
Waves push sand and pebbles up beach - “constructing” it
Destructive waves are formed by…
Local storms close to the coast
Destructive waves are common at what time of year?
Winter
What are characteristics of destructive waves?
Waves close together
Waves high + steep, plunge onto beach
Steep beach
Little forward swash, strong backwash erodes beach
What is weathering?
The weakening or decay of rock due to the action of weather, plants + animals
What are the three types of weathering?
Physical / mechanical
Chemical
Biological
What is physical / mechanical weathering?
The disintegration of rock - often results in scree at foot of cliff
What is chemical weathering
Caused by chemical changes - rainwater is slightly acidic + slowly dissolved certain rocks / minerals
What is biological weathering
Due to actions of flora / fauna - eg plant roots grow in cracks, animals burrow
What is an example of physical / mechanical weathering?
Freeze-thaw
Water enters fault in rock, freezes overnight and expands, widening fault
What is an example of chemical weathering?
Rainwater absorbs CO2 from air, becomes slightly acidic. Contact with alkaline rocks eg limestone / chalk creates chemical reactions, slowly dissolve
What is an example of biological weathering?
Tree roots - as vegetation roots grow they exploit weakness in cliff, widens faults and weakens structure of cliff
What is mass movement?
The downward movement of rocks and loose material under the influence of gravity
What are the four types of mass movement?
Rockfall
Landslide
Mudflow
Rotational slip
What is rockfall?
Fragments of rock break away from cliff face - often due to freeze-thaw
What is landslide?
Blocks of rock slide downhill
What is mudflow?
Saturated soil and weak rock flows down a slope
What is rotational slip?
Slump of saturated soil and weak rock along a curved surface
What is coastal erosion
The removal of material and the shaping of landforms
What are the processes of coastal erosion
Solution
Corrasion
Abrasion
Attrition
Hydraulic power
What is solution
Dissolving of soluble chemicals in rocks eg limestone
What is corrasion
Fragments of rock picked up by sea and thrown at cliff
They scrape and wear away the rock
What is abrasion
“Sandpapering” effect of pebbles grinding over a rocky platform - makes it smoother
What is attrition
Rick fragments carried by sea knock against each other - become smaller + more rounded
What is hydraulic power
Power of waves as they hit the cliff
Trapped air forced into cracks eventually causing rock to break up
Deposition happens when…
Water slows down and waves lose their energy
What are the four ways sediment is transported?
- Solution - dissolved chemicals in water, often derived from limestone or chalk
- Suspension - particles suspended within the water
- Traction - large pebbles roll along seabed
- Saltation - hopping / bouncing motion of particles too heavy to be suspended
How does hydraulic action/power erode cliffs?
Waves break against a cliff
Trapped air is forced into cracks in rock
Rock eventually breaks apart
The explosive force of trapped air in a crack is called…
Cavitation
Compare the two processes of sliding and slumping
Sliding is where rocks and loose material slide down a slope at quick speed
Slumping is a slower process where soil slides on a curved slip surface
What is longshore drift?
Where waves approach at an angle and sediment moves along the beach in a zigzag pattern
Movement of sediment on the beach depends on…
The direction that the waves approach the coast, as a result of the prevailing wind direction
If the waves approach “head on” then the sediment will move…
Up and down
Explain how longshore drift works
Waves approach at 45 degree angle
Sediment moves along beach in zigzag pattern
Swash carries sediment diagonally up the beach, backwash carries it back down
Deposition happens when…
Water slows down and waves lose their energy
How do arches, stacks and stumps form?
- Faults / weaknesses in resistant rocks are vulnerable to erosion
- Abrasion + hydraulic action widen fault, forming a cave
- Erosion causes two back to back caves to break through headland - arch
- Arch enlarged by erosion, roof eventually collapses
- Leaves isolated stack
- Stack is eroded - stump
How do hard and soft rocks affect landforms?
Hard rocks eg limestone, granite and chalk are more resistant to erosion than soft rocks eg clay
Harder rocks form cliffs and headlands, soft rocks form bays or low lying coastline
Geological structure includes the way…
Layers of rocks are folded / tilted
How does geological structure affect landforms?
Includes way layers of rock are folded
Faults are cracks in rocks - tectonic pressures can cause rocks to snap rather than fold
Movement / displacement happens either side of fault
What is a concordant coastline?
Rocks are parallel to wave front 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 are at right angles to sea
How do bays form?
Weaker bands erode more easily - form bays. As bays are sheltered Deposition takes place forming a beach
How do headlands form?
More resistant rocks are eroded more slowly - stick out into sea to form headlands
No beaches - erosion dominates in these environments - most erosion along landforms found at headlands
How is a wave-cut platform created?
Waves break against cliff - erosion forms a wave-cut notch
Over time it deepens + undercuts cliff
Eventually cliff collapses
Through this process the cliff gradually retreats leaving a gently sloping rocky platform (wave-cut platform)
Why is a wave-cut platform typically quite smooth?
Due to abrasion
What are the four coastal deposition landforms?
Beaches
Sand dunes
Spits
Bars
What are beaches?
Deposits of sand and shingle
Sandy beaches are mainly found…
The waves are…
In sheltered bays
Constructive
Along ___ energy coasts sand is ___ leaving a ___ beach
High
Washed away
Pebble
How are sand dunes formed?
Embryo dunes form around deposited obstacles eg wood or rocks
Dunes develop and are stabilised by vegetation to form fore dunes and tall yellow dunes
Rotting vegetation makes sand more fertile and plants grow on them
Ponds can form in depressions (dune slacks)
How is marram grass adapted to grow on dunes?
Adapted to windy, exposed conditions
Long roots to find water
These roots help bind sand together and stabilise dunes
What is a spit?
A long, narrow finger of sand or shingle jutting out into sea from land
How do spits form?
Longshore drift transports sand along coast, if coastline bends sharply sediment is then deposited at sea
It builds up and the end can become curved by winds or tidal currents (recurved end)
Salt marshes can form behind the spit as deposits of mud build up
What is a bar?
When longshore drift causes spits to grow across a bay
How do bars form?
A spit grows right across a bay due to longshore drift
It traps a freshwater lake (lagoon) behind it
How do offshore bars form?
Forms further out to sea
Waves approaching a gently sloping coast deposit sediment due to friction with seabed
Buildup of sediment offshore means waves break some distance from coast
In the UK some offshore bars have been driven onshore. Why does this happen and what is it called?
Rising sea levels
Called a barrier beach
What is the named example for coastal landforms?
Swanage
Where is Swanage?
South coast of England
Dorset
Different rock types reach the coast
Jurassic coast
What coastal features can you name at Swanage?
Old Harry Rocks - chalk headland, Old Harry is a stack
Ballard Point - chalk headland with caves, cracks and arches
Durlston Head - limestone headlands no arches yet because it’s very wide
Swanage Bay - bay with sand beach
Studland Beach - bay with sand beach, has embryo dunes and marram grass
What is hard engineering in coastal management?
Use of artificial structures to control natural processes
What are the hard engineering strategies for managing coasts?
Sea walls
Groynes
Rock armour
Gabions
What is a sea wall?
Concrete / rock barrier against sea (curved to reflect waves)
Advantages of sea wall?
Sense of security
Doesn’t impede sediment movement
Effective
Often creates a walkway
Disadvantages of sea wall?
Costs £5000-10,000 per metre
Visual impact
May destroy habitats
What are groynes?
Timber / rock structures out to sea (slow longshore drift by trapping sediment - allows beach to build up)
Advantages of groynes?
Larger beach - tourism, act as windbreak
Disadvantages of groynes?
Expensive, unattractive, starve other beaches of sediment
What is rock armour?
Large boulders at base of cliff - absorb energy of breaking waves to protect cliffs
Advantages of rock armour?
Relatively cheap compared to sea walls
Easy to maintain
Disadvantages of rock armour?
Imported rocks - cost + rocks don’t blend with local geology
Regular maintenance needed
What are gabions?
Wire cages of rocks at cliff base - absorb wave energy, support cliff
Advantages of gabions?
Can be visually appealing if vegetated + well maintained
Can improve cliff drainage
Disadvantages of gabions?
Easily damaged - rust within 5-10 years
Unattractive
Expensive
What are the soft engineering strategies for managing coasts?
Beach nourishment + re-profiling
Dune regeneration / stabilisation
Dune fencing
What is beach nourishment and re-profiling?
Adding sediment to beach to make it wider and higher
Advantages of beach nourishment and re-profiling?
Sediment is obtained offshore locally so blends in
Wider beach attracts tourists
Disadvantages of beach nourishment and re-profiling?
Cost (although less than hard engineering)
Needs constant maintenance
What is dune regeneration / stabilisation?
Sand dunes are effective coastal defenders but are easily damaged
Marram grass planted to stabilise dunes
Fences to prevent people walking on them
Advantages of dune regeneration / stabilisation?
Cheap
Natural
Maintains habitats
Disadvantages of dune regeneration / stabilisation?
Time consuming
People may continue to damage dunes
What is dune fencing?
Fences constructed to encourage dune formation
Advantages of dune fencing?
Minimal environmental impact
Protect existing dunes / habitats
Disadvantages of dune fencing?
Can be ugly especially if broken
Need regular maintenance
What is managed retreat?
The deliberate policy of allowing the sea to flood or erode an area (this area is often of low value)
What are the advantages of managed retreat?
Allows natural processes to take place - less intrusive than hard engineering
Long term, sustainable
Generally less expensive
What is the named example of a managed retreat?
Medmerry
What is the coast at Medmerry mostly used for?
Farming and caravan parks
Where is Medmerry?
Near Chichester, in southern England
Why did Medmerry need a new coastal defence scheme?
Previously protected by a low sea wall
Was in need of repair - would cost too much
What happened in 2013 at Medmerry?
The sea was allowed to breach the sea wall and flood some farmland
How much did the Medmerry scheme cost?
£28 million
How have farmland, roads and settlements been protected in the Medmerry scheme?
Embankments built inland
How is the Medmerry scheme sustainable / helping the future?
Creates large natural salt marsh - natural buffer against sea
Protects surrounding farmland and caravan parks from flooding
Encourages tourism
Establishes valuable wildlife habitat
Where is Lyme Regis?
Coastal town in Dorset, on England’s south coast - popular for tourists
What are the issues at Lyme Regis?
Much of town built on unstable cliffs
Coastline is eroding more rapidly than any in Europe - powerful waves from SW
Many properties destroyed / damaged and sea walls breached many times
When did Phase 1 of the Lyme Regis scheme take place and what did it involve?
1990s
New sea wall and promenades
Winter of 2003-4 emergency project to stabilise cliffs - nails to hold rocks together, improved drainage, reprofiling of beach
When did Phase 2 of the Lyme Regis scheme take place and what did it involve?
2005-2007
New sea walls and promenades
Creation of wide sand + shingle beach to absorb wave energy
Extension of rock armour to absorb wave energy and retain beach
When did Phase 4 of the Lyme Regis scheme take place and what did it involve?
2013-2015
Cost £20 million
New sea wall for extra protection
Nailing, piling and drainage to stabilise cliffs - to protect homes
Why didn’t the planned Phase 3 go ahead at Lyme Regis?
Costs outweighed benefits
How much did the Lyme Regis scheme cost overall?
Over £43 million
What have been the positive outcomes of the Lyme Regis scheme?
New beaches = increased tourism + seafront businesses thrive
New defences have withstood storms
Harbour more protected - benefits fishermen and boat owners
What have been the negative outcomes of the Lyme Regis scheme?
Increased visitors - conflict w locals (traffic and litter)
Some think new defences have spoilt landscape
What is a drainage basin?
Area of land drained by a river and its tributaries
What is a tributary?
A small stream joining a larger river
What is a watershed?
The edge of a river basin
What is the mouth of a river?
End of a river, usually where it joins the sea
Describe the cross profile of the upper course of a river valley
Lots of vertical erosion
Valley: steep sided, V-shaped
River: narrow, shallow, turbulent
Describe the cross profile of the middle course of a river valley
Lateral erosion
Valley: wider, flat floor
River: wider and deeper
Floodplain
Describe the cross profile of the lower course of a river valley
Lateral erosion
Valley: very wide and flat
River: wide, deep, with large sediment load
Floodplain and levees
How does a river’s long profile change?
Steep gradient in upland areas
Gentle gradient in lowland areas
Material transported by a river is called its…
Load
Where are erosion and deposition landforms most common in the course of a river?
Upper: mostly erosion (eg waterfalls)
Middle: erosion + deposition (eg meanders)
Lower: mostly deposition (eg levees)
When does deposition happen in rivers?
When the river’s velocity decreases and it no longer has the energy to transport its load
Larger rocks are deposited in the ___ course of a river
They are mostly transported by ___ for ___ distances during periods of ___ flow
Upper
Traction
Short
High
Finer sediment is carried further ___ mostly in ___
It is deposited on the ___ and ___ where velocity slows due to ___
Downstream
Suspension
Bed
Banks
Friction
Lots of deposition occurs at a river’s ___ where velocity reduces because of interaction with ___ and the ___ gradient
Mouth
Tides
Gentle
How is a waterfall formed?
River flows over variety of rock types
More resistant rocks form steps which form waterfalls
Water flowing over resistant rock forms a plunge pool where hydraulic action + abrasion undercut rock
Eventually overhang collapses, waterfall retreats upstream
What is the other way for waterfalls to form?
When sea level drops causing a river to cut down into its bed
This creates a step called a knick point
What is a gorge?
A narrow steep sided valley found downstream of a waterfall
How is a gorge formed?
By the gradual retreat of a waterfall over hundreds / thousands of years
What are the other two ways gorges can form?
At end of last glacial period, water from melting glaciers poured off upland areas forming gorges (eg Cheddar)
Some form on limestone as result of collapse of underground caverns
What are interlocking spurs?
Projections of high land that alternate from either side of a V shaped valley
How are interlocking spurs formed?
By fluvial erosion
Found in upper course where rocks are resistant - river not powerful enough to cut through them, so flows around them
What is hydraulic action in rivers?
Force of water hitting river bed and banks
Most effective at high volume + velocity of water
What is abrasion in rivers?
Load carried by river hits bed or banks, dislodging particles
What is attrition in rivers?
Stones carried by river knock against each other, becoming smaller and more rounded
What is solution in rivers?
Alkali rocks eg limestone are dissolved by slightly acidic river water
What are solution, suspension, traction and saltation in rivers?
Solution - dissolved load
Suspension - small sediment held in river
Traction - large particles rolled on riverbed
Saltation - bouncing of particles too heavy to be suspended
What is fluvial erosion?
The process by which the flow of a river wears away the land around it, including the river bed and banks
What is a meander?
A bend in a river - found mainly in lowland areas, common in middle course of river
In the early stages of meander formation, water flows slowly over shallow areas (___) and faster through deeper sections (___)
Riffles
Pools
What is helicoidal flow?
A motion that corkscrews across from one bank to another
What is the thalweg?
The line of fastest current - swings from side to side causing erosion on outside bend and deposition on inside
Fast flowing water causes ___ erosion which undercuts the bank and forms a ___
Lateral
River cliff
Vertical erosion on the ___ bend which deepens the river bed, resulting in an ___ cross profile
Sand and pebbles are deposited on the ___ bend where the current is ___ forming a ___
Outside
Asymmetrical
Inside
Slower
Slip off slope
