coasts and rivers Flashcards
1
Q
What is erosion?
A
When a rock or particle is worn down by a process involving movement.
2
Q
What is weathering?
A
the wearing down or breaking of rocks while they are in place
3
Q
What is abrasion ?
A
- Rocks are hurled at the cliff face by powerful waves
- The rocks that have been hurled chip/break off parts of the cliff face
- Gradually wears away the cliff face over time
4
Q
What is attrition?
A
- Large angular rocks hit against each other in the water due to waves and current
- The rocks wear each other away, breaking off smaller bits of rock
- Eventually the rocks become smaller and rounder like pebbles
5
Q
What is solution / corrosion?
A
- when sea water dissolves certain types of rocks
- The pH of water is not always neutral
- Sometimes chemicals react with/dissolve parts of rock types
- E.g limestone
6
Q
What is hydraulic action?
A
- Powerful waves hit the cliff face
- Water forced into lines of weakness/cracks compresses the air, creating a high build up of pressure
- This pressure causes the crack to widen
- Eventually the crack becomes so big that small parts of the cliff face break off
7
Q
What 3 things affect the size and energy of waves?
A
1) How long the wind has been blowing.
2) The strength of the wind.
3) How far the wave has traveled.
8
Q
What are the swash and backwash?
A
Swash is when a wave is washed up the beach, backwash is when it runs back down.
9
Q
What is a fact about constructive (calm) waves?
A
The swash is stronger than the backwash.
10
Q
What is a fact about destructive waves.
A
The backwash is stronger than the swash.
11
Q
What is fetch?
A
The distance that the wind blows over the surface of the sea.
12
Q
1 What is hard engineering?
2 what is soft engineering?
A
- Man made
expensive
short term
high impact on environment and landscape. - Better for environment
less expensive
long term.
13
Q
What are sea walls?
A
Sea walls reflect the ways energy and protects the cliff behind.
They last a long time and are most effective and let’s tourists have something to walk on. It’s very expensive however and is also not very environmentally helpful.
13
Q
What is rock armor?
A
Rock armour absorbs waves energy.
It’s very effective and is good for animals and it disperses energy.
However the rock is imported and it’s expensive.
14
Q
What are revetments.
A
structures that allow sea water and sediment to pass through, but the structures absorb wave energy
15
Q
What are gabions?
A
Gabions absorb the waves energy.
The last 20 to 25 years and are made up by local materials.
They are also one of the cheaper options. However there may be environmental concerns and the metal rust.
16
Q
What are groynes?
A
They are walls that prevent erosion.
17
Q
what are the outputs on the coastline?
A
loss of wave energy
depositional landforms
erosion landforms
18
Q
what are the inputs into the coastline?
A
wave energy
tides
currents
winds
tidal waves
changes in sea level
sediment
human activity
19
Q
Formation of Waves
A
Wind Blows Over the Sea → Friction between wind and water creates ripples.
Energy Transfer → Wind transfers energy to the water, forming waves.
Circular Motion of Water Particles → Water particles move in a circular motion but don’t travel forward.
Wave Approaches Shore → As the wave moves into shallower water, friction with the seabed slows the bottom of the wave.
Wave Breaks → The top of the wave continues moving faster than the bottom, causing it to topple over and break onto the shore.
Swash and Backwash → Water rushes up the beach (swash) and returns to the sea (backwash), shaping the coastline.
20
Q
Chemical Weathering
A
- Rain can be slightly acidic sometimes
- The acid rain reacts with certain rock types
- Specifically with limestone
- The calcium carbonate reacts with the acid, forming bicarbonates
- This is soluble and easily carried away in solution, therefore wearing away the rock
20
Q
Biological Weathering
A
- A seed may fall into a crack in a rock
- As the seedling germinates and grows, its roots widen the crack
- The crack is weakened and rock may break away
- This can also occur when animals burrow in cracks in rocks
21
Q
Wave Cut Notch & Platform
A
- Base of the cliff is eroded by destructive waves and erosional processes
- Cliff begins to retreat, forming a wave cut notch
- Erosion continues, but the overhang becomes unstable as it is unsupported
- Gravity eventually pulls down the overhand, the debris left behind forming a wave cut platform
- As the width of the platform increases, the power of the sea decreases as the waves have further to travel
22
Q
Headlands & Bays
A
- Coastlines are usually made up of cliff faces with both hard and soft rock
- Soft rock is eroded more quickly, whilst hard rock is much more resistant
- As the soft rock is eroded quickly, a bay is created, and the hard rock protrudes out into the ocean as is known as a headland
22
Caves, Arches, Stacks & Stumps
- Cave: The sea erodes lines of weakness with erosional processes. Cracks become bigger and bigger, gradually forming a cave
- Arch: This occurs on both sides of the headland, eventually the caves both erode through completely, forming an arch.
- Stack: Due to the arch being unsupported, it will collapse under its own weight, leaving behind a stack
- Stump: The stack is weathered and eroded, therefore the stack collapses
22
Spit
- Longshore drift transports material down the coastline
- When there is a sudden change in direction of coastline, the material is deposited in the shallow sea
- This continues, more sand and material is deposited in the shallow sea
- The spit extends out into the sea, and the end is usually curved in like a hook
- The end is hooked as secondary winds may make it difficult for the spit to continue to extend, or an estuary's currents may make it difficult for the spit to extend
23
Bar
- Longshore drift transports material down a coastline
- A bar is formed as a spit extends across a bay, joining up the 2 headlands
- The area behind the bar is called a lagoon
24
Longshore Drift
- This is the transport of material down a stretch of coastline
- Caused by waves approaching the beach at an angle
- Backwash is always at right angles to the beach due to the pull of gravity
- Eventually the material transported is deposited as the waves lose energy, or because a coastal defence is in the way
25
Swash
The resulting forward movement of water that runs up the beach until it runs out of energy.
26
Backwash
The water that runs back down the beach under gravity.
27
Weathering
Breakdown of rocks which is caused by freeze-thaw, growth of salt crystals, acid rain and the growth of vegetation roots.
28
formation of an oxbow lake
An oxbow lake is formed when a meandering river or stream erodes the outer banks of a bend, while the inner banks are deposited with sediment. Over time, this erosion and deposition cause the bend to become more pronounced, until the neck of the meander narrows and eventually breaks through during a flood. The river then takes a new, straighter course, leaving behind a crescent-shaped oxbow lake.
29
Tombolos
These are spits that have continued to grow seawards until they reach and join an island. Longshore drift and offshore sediments being rolled towards the coast also helps with the formation.
30
When does mechanical weathering happen? (River)
This happens when rainwater enters cracks or gaps in the rock and then freezes if temperatures drop below zero. The water expands as it turns into ice and then exerts pressure on the rock causing it to break into smaller pieces
31
What is chemical (acid rain) weathering? (River)
All rainwater is slightly acidic. If the air is polluted by factories and vehicles, it can become more acidic. When rain falls on rocks, the acid in it can react with weak minerals, causing them to dissolve and the rock to decay.
32
What is biological weathering? (River)
The roots of plants, especially trees can grow into cracks in a rock and split them apart
33
What is traction?
What is suspension?
What is saltation?
What is solution? (In transportation)
It is a form of transportation, for when large boulders are rolled along the river bed
It is a form of transportation for when finer sand particles are carried along in the flow, giving a brown appearance
It is a form of transportation for when smaller pebbles are bounced along the river bed, picked up then dropped as the river flow changes
For when minerals, such as chalk are dissolved in the water and carried along in the flow, although they cannot be seen
34
describe the gradient in the upper, middle and lower course
Describe the discharge in the up, mid, low course
Describe the depth in the up, mid, low course
Describe the channel shape in the up, mid, low course
Describe the velocity in the up, mid, low course
Describe the valley profile in the up, mid, low course
Describe the features in the up, mid, low course
Describe the sediment shape and size in the up, mid, and low course
Upper - steep
Middle- less steep
Lower - shallow gradient
Up - smaller
Mid - large
Low - very large
up -shallow
mid - deeper
low - deep
Up - narrow, steep sides
Mid - flat, steep sides
Flat floor, gently sloping sides
Up - quite fast
Mid - fast
Low - very fast
Up - steep sides
Mid - flat with steep sides
Low- flat with gently sloping sides
Up - waterfalls, interlocking Spurs
Mid - meanders, floodplain
Low- meanders, floodplain, levées, ox-bow lakes
Up - angular boulders
Mid- more rounded rocks
Low - smooth, rounded pebbles
35
What are interlocking Spurs?
Near the rivers source, rivers are small and do not have a lot of power. They tend to flow around valley slide slopes, called Spurs, rather than being able to erode them. The Spurs are left interlocking, with those from one side of the valley overlapping with the Spurs on the other side
36
How are waterfalls formed?
A waterfall is formed along a river when a band of hard, more resistant rock lies over a band of soft, less resistant rock. The river erodes the less resistant rock at a faster rate, gradually undercutting the more resistant rock. The continued erosion of the soft rock by abrasion and hydraulic action causes an overhang of the hard rock. Eventually the hard rock cannot support its own weight and collapses under the force of gravity. The force of the falling water and abrasion by large angular boulders leads to erosion of the river bed and formation of a plunge pool
37
How are gorges formed?
After a waterfall is formed, as the soft rock continues to be eroded and the hard rock collapses, a steep-sided gorge is formed as the waterfall retreats upstream. Gorges form in hard rocks, where vertical erosion by rivers is dominant.
38
What is the weathering process?
he physical or chemical break down of rock or soil in the place where the rock/soil is located
- called 'in situ'.
- No material is transported when an "in situ" rock is weathered, however its shape may change
39
How is a plunge pool formed?
Hydraulic action and abrasion
40
What is a floodplain?
A floodplain is the area around the river that us more liable to flood. It is formed by erosion and deposition.
Most floodplains are formed by deposition on the inside of river meanders and by overbank flow. Wherever the river meanders, the flowing water erodes the river bank on the outside of the meander. At the same time, sediments are simultaneously deposited in a bar on the inside of the meander.
41
What are levees?
Levees are natural embankments of sediment formed along the banks of rivers that carry a large load and occasionally flood.
In times of flood, water and sediment come out of the channel as the river overflows its banks.
As it overflows, the river immediately loses velocity and energy and deposits the larger and heavier sediment first, on its banks, repeated flooding causes these banks to get higher, forming levees.
42
What is the difference between infiltration and percolation?
Infiltration is water moving from the surface into the soil, while percolation is water moving through the soil after infiltration
42
What are meanders?
Meanders are bends found in a rivers course, commonly found on a rivers flood plain.
Continuous erosion on the outer bank and deposition on the inner bank forms a meander in the river, which will migrate downstream and change shape over time.
43
What is interception?
Interception is how precipitation is prevented from reaching the ground, usually by being caught on leaves or branches
44
Define the term groundwater flow.
Groundwater flow is the movement of water through rocks.
45
What is through flow?
Through flow is the lateral movement of water within the soil.
45
What is a drainage basin?
A drainage basin is an open system that drains all the water which lands on the Earth's surface. Every drainage basin is covered by a network of tributaries which connect to a main river channel.
45
Define the term watershed.
A watershed, also known as a drainage basin, is an area of land where all water drains to a central point like a lake, river, or stream.
46
What is a confluence?
A confluence is where two rivers or streams join together.
47
Define the term drainage density.
Drainage density refers to the number of tributaries in a drainage basin. To calculate the drainage density the area of drainage basin is divided by the number of tributaries.
47
What is a tributary?
A tributary is a smaller stream or river that flows into a larger stream or main river.
48
Define the term bedload.
Bedload is the heaviest material carried by a river, typically along the river bed.
49
Name two upland river landforms?
Upland river landforms include:
Waterfalls.
Gorges.
V-shaped valleys.
Interlocking spurs.
50
Define the term plunge pool.
A plunge pool is a deep pool at the base of a waterfall formed by hydraulic action and abrasion.
51
name hazards of flooding.
The spread of water-related diseases.
Deaths and injuries.
Damage to infrastructure.
Erosion of river banks.
Destruction of crops.
52
What is a flood hydrograph?
A flood hydrograph is a graph showing changes in river discharge after a storm event.
53
Define the term lag time.
Lag time is the time taken for precipitation to reach the river from where it falls.
54
What is river restoration?
River restoration is a soft engineering technique that supports the river by restoring it back to its original regime.
55
how do waves break
When a wave reaches shallow water, its height increases while its wavelength decreases. This makes the wave steeper. As the wave continues to grow taller and closer together, it becomes less stable and eventually breaks.
56
what is longshore drift
Longshore drift is the movement of material along the shore by wave action
It happens when waves approach the beach at an angle.
The swash (waves moving up the beach) carries material up and along the beach.
The backwash (waves moving back down the beach) carries material back down the beach at right angles.
57
what are coral reefs
Massive structures made of limestone deposited by coral polyps.
58
where are coral reefs found
Coral reefs are often found in the Indian and Pacific Ocean as there are warm currents.
This is why they are usually not found in the west coast of America and in southern africa as the currents are cold and strong so they wouldn't survive the conditions.
59
conditions for corals (5)
-High tides (cant survive above the water)
-Warm water (don't tolerate temperatures under 18 degrees).
-Breaking waves which give them food and oxygen
-Shallow water - otherwise it gets cold as there is no sunlight deep in the water.(can't be below 50 feet as they need algae to live)
-Clear water (without sediments) otherwise there is sediments in suspension and the sunlight cannot penetrate
59
3 types of coral reefs
fringing (most common)
-Close to the shore
-Can be attached to shore or separated from it by a narrow strip of water called a lagoon
barrier
-Farther offshore
-Deep
atoll
-Rings of coral surrounding a body of water like a lagoon
-Begin as a fringe reef surrounding a volcanic island
-As the coral expands and grows the island sinks into the ocean leaving the ring of coral
