9014531
Description
Flashcards by Natalia Cliff, updated more than 1 year ago
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Created by Natalia Cliff
over 7 years ago
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| Question | Answer |
| What affects the formation of a wave? | -Fetch -Strength of the wind -Obstacles |
| Why do waves break? | -Out at sea, waves have a circular orbit -When they come into land, friction with the seabed makes the orbit elliptical -The orbit becomes more elliptical due to increased friction until the top of the wave breaks |
| Diagram of waves breaking |
Image:
Waves Breaking (image/jpeg)
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| Characteristics of constructive waves | -Weak backwash -Strong swash -Means that it deposits -Formed by distant storms |
| Characteristics of destructive waves | -Weak swash -Strong backwash -Means it erodes -Closely spaced and interfere with each other resulting in chaos -Crash down on the beach -Formed by local storms |
| What are the 3 kinds of weathering? | -Chemical (e.g. salt water against certain rocks) -Biological (e.g. tree roots) -Physical/Mechanical (freeze thaw) |
| What are the kinds of mass movement? | -Rockfall -Landslide -Mudflow -Rotational slip |
| What happens in Rockfall? | fragments of rock break away from the face of the cliff, usually due to freeze thaw |
| What happens in a Landslide? | blocks of rock slide downhill |
| What happens in a Mudflow? | Saturated soil and weak rock flows down |
| What happens in a Rotational Slip? | slump of saturated soil and weak rock along a curved surface |
| Types of erosion at the coast | -Hydraulic power -Corrasion -Abrasion -Solution -Attrition |
| Corrasion | Fragments of rock being picked up and hurled at the cliff by the sea |
| Hydraulic power | the sheer force of the waves breaking bits off cliffs |
| Abrasion | The sandpapering effect of pebbles grinding over a rocky platform |
| Attrition | fragments of rock caught by the sea knock against one another, causing them to be smaller and rounder |
| Solution | Some rocks (e.g. limestone and chalk) are susceptible to being dissolved by saltwater |
| Types of Transportation | -Traction -Saltation -Suspension -Solution -Long shore drift |
| Traction | large pebbles rolled along the seabed |
| Saltation | hopping or bouncing motion along the sea bed of particles too heavy to be suspended |
| Suspension | particles carried by the water |
| Solution | dissolved chemicals, often derived from chalk and limestone |
| Longshore drift | -Waves approach beach at the angle of the dominant wind (north west in northern hemisphere) -Retreat at 90 due to gravity -Causes zigzagging motion that carried sediment along the beach |
| Where does deposition occur? | Deposition tends to occur in bays, where the energy of the wave is reduced |
| Formation of headland and bays | -Bands of resistant (hard) and less resistant (soft) rock -Soft rock get's eroded away over time -Leaves headlands of hard rock and bays of soft rock |
| Diagram for formation of headlands and bays | |
| Formation of a wave-cut notch | -Waves break against a cliff -Erosion (hydraulic action and corrasion) occurs near the high tide line -Over time the notch gets deeper -The cliff can no longer support itself, so collapses |
| Formation of a wave-cut platform | -Continual wave-cut notches and cliff collapse the cliff line retreats -This leaves behind a gently sloping rocky platform called a wave-cut platform -Normally very smooth due to abrasion |
| Diagram of cliff collapse (including mass movement, wave-cut notches and wave-cut platforms) |
Image:
Cliff Collapse (image/jpeg)
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| Formation of a stump | -Headland sticks out to sea with a lot of destructive wave -Corrasion and hydraulic action erode a crack in the headland -Crack get's eroded into a cave -Eventually breaks through to the other side, leaving an arch -Top of the arch collapses due to lack of support and gravity leaving a stack -Stack is eroded down to a stump by weathering |
| Formation of a stump diagram |
Image:
Stump (image/jpeg)
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| Beaches | -Beaches are a deposition of sand and shingle -Sandy beaches are often found in sheltered bays -Waves refract as they enter the bay and therefore lose their energy so deposition occurs |
| Formation of a spit | -Spits occur when there is a break in the coast -Longshore drift continues depositing however -Eventually the spit breaks the surface forming new land -If there is a wind opposing the prevailing wind it can form a hook at the end |
| Diagram of the formation of a spit |
Image:
Spit (image/jpeg)
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| Formation of a bar | -Sometimes long shore drift continues and the spit grows across the bay, leaving a freshwater lagoon behind it |
| Rising Sea Levels | -Over the last 15 years seas have risen by 3 mm -Predicted 28-43 cm by the end of the century -Caused by thermal expansion of seawater |
| Rising Sea Levels Norfolk | -Norfolk broads is a popular tourist destination -Brings £5+ mill to the local area -Rising sea levels would cause bad flooding |
| Rising Sea Levels Happisburgh | -Rising sea levels will probably mean an increase in erosion -Threatens settlements of cliffs like Happisburgh -Coastal defences will be expensive |
| Rising Sea Levels East Anglia | -Storm surge in 1953 that killed 300 people -Such occurrences more likely with rising sea levels -22% of East Anglian salt marshes could be gone by 2050 |
| Rising Sea Levels Thames Barrier | -Protects buildings worth £80 bn -needs replacement in the next 30 to 50 years -As sea levels rise lower areas of Thames estuary at risk of flooding -Affects housing and farmland |
| Barton-on-Sea Hampshire Location and Issue | -Stretch of coastline in Christchurch bay -Number of buildings lost due to cliff collapse -Extensive coastal defences built, but new landslip in 2008 -Development of houses just 20 m from cliff edge -Estimated that they will be lost in 10 to 20 years -Rate of erosion up to 2 m |
| Barton-on-Sea Hampshire Natural causes | -Rocks are weak sands and clays, easily eroded and little resistance to cliff collapse -Permeable sand over impermeable clay causes water to pond up and increase the weight and pressure of the cliff -Faces prevalent westerly winds with a long fetch -Several small streams flow toward the cost but disappear in permeable sand |
| Barton-on-Sea Hampshire Human causes | -Buildings of cliff top have made it heavier and more prone to collapse |
| Shoreline management plan | an integrated coastal management plan for a stretch of coast Details areas of high risk of erosion, flooding etc. and puts plans into place for how to cope with the issues |
| Sea Wall Description and cost | -Concrete or rock barrier built at the foot of a cliff or the head of a beach - 3-5 m high -curved face to reflect waves -Up to £10 million per km |
| Sea Wall Advantages and disadvantages | -Effective -Often has a walkway for people -Can be obtrusive -Very expensive -High maintenance costs |
| Groynes Description and cost | Timber or rock structures built out to sea from the coast -Trap sediment moving from longshore drift -Wider beach offers more protection -Up to £5 000 per m |
| Groynes Advantages and Disadvantages | -Bigger beach for tourists -Useful structures for fishing -Not too expensive -Starve beaches downdrift thereby increasing erosion there -Unnatural and can be unattractive |
| Rock Armour Description and Cost | -Piles of large boulders dumped at the foot of a cliff -Force the waves to break and absorb their energy -£1 000 - £4 000 per m |
| Rock Armour Advantages and disadvantages | -Cheap and easy to maintain -Often used for fishing -Rocks from elsewhere in the country can be expensive to transport -Can be obtrusive -Don't fit with natural geology |
| Beach Nourishment Description and cost | -Adding sand or shingle to a beach -Sediment obtained locally so blends in -£3 000 per m |
| Beach Nourishment Advantages and Disadvantages | -Relatively cheap -Easy to maintain -Blends in -Bigger beach means more tourists -Needs constant maintenance unless structures are built to keep it in place |
| Dune Regeneration Description and cost | -Sand dunes are easily destroyed -So marram grass is planted to stabilise the dunes -Areas are then fenced off to keep people off the newly planted dunes -£20 per m |
| Dune Regeneration Advantages and disadvantages | -Natural coastal environment for people and wildlife -Relatively cheap -Planting is time consuming -Can be damaged by storms -People don't like being fenced off |
| Marsh Creation Description and cost | -Type of managed retreat -Low-lying coastal areas are flooded to become salt marshes -Salt marshes are effective barriers against the sea -Cost depends on value of land -£5 000 - £10 000 per ha |
| March Creation Advantages and disadvantages | -Cheap in comparison to expensive defences for low-value land -Much needed habitat for wildlife -Land is lost -Farmers/landowners need to be compensated |
| Managed retreat | Allowing controlled flooding of low-lying areas or cliff collapse in areas where the value of the land is low, e.g. poor quality grazing land |
| Minehead Location and Issue | -North Coast of Somerset -:Large tourist resort -1990s realised if nothing was done, storm damage would cost £21 m -1997 sea defences officially opened -Cost £12.3 m |
| Minehead Main features | -o.6 m high curved sea wall -Rock armour at the base of the wall Beach nourishment built the beach up 2 m in height -Four rock groynes retain the beach -Wide walkway for tourists |
| Salt Marsh | -Starts as an accumulation of mud behind a spit -Mud breaks the surface forming mud flats -Pioneer plants with high salt tolerance (cordgrass) called pioneer plants grow on these -Cordgrass has a high salt tolerance and long rots stop it from being swept away -Tangled roots keep mud in place -Mud level rises and is no longer often covered by water -Rainwater washes out salt -New plants (e.g. sea asters) start to colonise -Slowly succession of plants develops called vegetation succession |
| Vegetation succession diagram | |
| Keyhaven, Hampshire Species | -Cordgrass -Ringed Plover (bird, feeds and nests in salt marsh) -Sea Lavender -Oystercatcher (bird, feeds and nests in salt marsh) -Wold Spider (clings to submerged stems of cordgrass waiting for low tide to bring it food |
| Keyhaven, Hampshire Issues | -Salt marsh retreating 6 m a year -1989 storm breached Hurst Castle Spit, exposing 50 - 80 m that was eroded in 3 months -Tourism means people could trample, park and pollute the saltmarsh |
| Keyhaven Hampshire Solutions | --1996 Rock armour and beach nourishment protected spit £5 m -Keyhaven is a SSSI and Nation Nature Reserve |
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