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65 Cards in this Set
- Front
- Back
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Features of beaches
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Bays
Headlands Sand Ridges+runnels Shingle Berms Storm beach Beach cusps Swash aligned beaches Drift aligned beaches |
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How are bays made
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There is a band of hard rock in front of soft rock
The hard rock is eventually eroded by the sea through abrasion, attrition, hydraulic action and corrosion This then exposes the softer rock behind The soft rock si eroded as a quicker rate and the erosion is in a circular shape, due to the faster erosion Over time beaches are formed due to an increase in deposition and decrease in erosion |
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How are headlands made
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Harder more resistant rock is found at the headland, and softer rock is found around it
This means erosion around the headland is faster due to the softer rock eroding first, this leaves the harder rock jutting out to form the headland The wave energy concentration is at the headlands with the rest of the sediment forming a bay |
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How is a spit formed
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DEPOSITION
Prevailing wind causes longshore drift to carry sediment along coastline The material is deposited and forms a spit Over time the spit grows, A hook develops if wind direction changes Waves can't pass the spit, so a sheltered area is created where silt is deposited and salt marshes form |
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How are ridges and runnels formed
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Formed at sand beaches at places with low water
When there is low tides and strong wind, the blown sand can accumulate into the runnels and ridges |
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What are berms and how are they created
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Smaller ridges that develop at high tide mark
Develop from deposition at top of the swah Generally created by small waves with less energy |
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What are storm beaches
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At the back of the beach, during a storm there is a very strong swash and this may deposit larger materials, forming a storm beach
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What are beach cusps
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Small semi-circular depressions
The sides of the cusp channel the incoming swash into the centre of the depression causing a stronger backwash which drags material down the beach from the centre of the cusp |
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What are drift aligned beaches
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When sediment is transferred along the coast by longshore drift
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What are swash aligned beaches?
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When the sediment moves up and down without lateral transfer (without changing sediment cells)
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Sand dunes
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Pioneer community
Yellow Mobile Dunes Grey Dunes Dune Slacks Dune Heath |
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Sand dunes pH
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decreases further along the dune system
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Typical plant types in each of the dune systems
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Embryo- lyme grass, sea couch grass
Foredunes- marram grass, sea couch grass Main ridge- marram grass, sand sledge Fixed dunes- marram, red fescue Dune slack reeds Dune heath- gorse, bracken Climax community- pine |
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How do pioneers start the formation
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Roots stabilise the ground and humus acts as nutrients to make sand hospitable
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Why are yellow mobile dunes yellow and mobile
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They contain little organic matter
Not yet fixed |
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Why are the grey dunes grey and fixed?
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The embryo grows bigger and their initial yellow colour darkens to grey as humus is added to the soil
Fixed as there is more colonisation of new species |
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What are dune slacks
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Depressions in dunes where it is damper (water table closer to surface)
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Why are plants like heather and birch found in the Dune Heath?
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Soil is more acidic, humus rich and water retentive
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How are blow-outs formed
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1. Dune intact with vegetation
2. Trampling/sitting on sand dunes damages vegetation 3. Plants become damaged and destroyed 5. High winds and storm removes the sand |
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What does wave energy depend on
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Strength of wind
Length of time the wind blows Fetch (distance the wind blows over open water) |
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Wave frequency
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The number of wave crests passing point A each second
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Wave period
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The time taken for the wave crest point A to reach point B
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Wave length
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The distance between two crests
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Wave height
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The height from the trough to the crest
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What is the swash?
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The rush of water up the beach
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What is the backwash?
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The water running down the beach, into the sea
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Features of a storm wave
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Localised
Higher waves Shorter wave length Generated by local winds |
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Features of a swell wave
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Found in open water
Low in height (less than 15m) Long wave length Travels long distance |
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Features of a constructive waves
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Low energy
Strong swash, weak backwash (sediment left onshore) gentle beach profile surging, low waves Low wave in proportion to length |
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Land features made by constructive waves
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Berms, ridges, runnels
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Features of destructive waves
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High energy
Weak swash, strong backwash (sediment pulled offshore) Steeper beach profile- pebbles High and frequent plunging waves Tail breaker breaks downwards with a great force More common in winter |
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Land features made by destructive waves
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Breakpoint bars, storm ridge
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Wave refraction
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1. Wave front approaches parallel to coast
2. Wave energy exerted at right angles to wave front 3. Wave reaches shallower water at headland- friction slows down wave velocity 4. Rest of wave is still in deep water, so continues at original speed 5. Difference in speed causes wave front to bend to the shape of the coastline 6. Wave energy is exerted at right angles to wave front- so energy is now concentrated on headland and dispersed in bays |
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Neap tides
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Lowest monthly tidal range
Occurs at 1/4 moons, where gravitational forces of moon and sun are perpendicular |
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Spring tides
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Highest monthly tidal range
Occur when Earth, Sun and Moon are in line Gravitational forces affect tide |
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Storm surges are caused by
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Changes in the sea level
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What is the change in sea level (that creates storm surges) due to
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Low air pressure
High wind speeds Increased by high tides, low lying land and funnel shaped coastline |
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What are sediment cells
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Setions fo the coastine where inputs and outputs are in equilibrium
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What are sediment cells seperated by
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Headlands, deep stretches of water etc
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When is the biggest tidal range?
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During the equnox- March and September
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Hydraulic Action
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Breaking wave traps air as it hits cliff face. The force of water compresses the air into a gap in the rock face, releasing pressure and causing air bubbles to explode and weaken cliff
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Abrasion
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The material in the sea is carried by the waves and grinds against cliff surfaces
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Attrition
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Rocks and pebbles in the sea knock together and erode into smaller, smoother bedload
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Solution
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Sea is acidic and this can dissolve the rocks
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What factors affect rate of erosion??
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Wave steepness and breaking point
Fetch Sea depth Coastal configuration (eg headlands) Beach presence Human activity |
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Why are some rocks more prone to erosion?
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Less resistant rocks erode more easily
Well jointed rocks are more prone to erosion Permeable rocks are less prone to erosion Resistant rocks have slow erosion rates Coarse grained rocks weather more rapidly (sandstone, gravel) |
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What does the resistance of a rock depend on
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Minerals of the rock, how they are cemented together, how compressed they are
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What is a concordant coastline
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Where rock layers are parallel
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What is a discordant coastline
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Where rocks are at right angles to the coast
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Explain longshore drift
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1. Wave comes up diagonally and moves pebble up
2. Pebble moves back as wave moves away 3. When there is a bend on the coast, sediment carries on straight to create a spit |
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Drift aligned beaches
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Waves break at an angle to the coast so swash occurs at an angle, but backwash runs perpendicular to the beach
As a result, material is transported along the beach via LSD |
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Swash aligned beaches
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Waves break in line, parallel to the coast. Swash and backwash moves material up and down the beach
Swash aligned beaches are smoothly curved and concave |
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What are sub-aerial processes and the two headings
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Land based processes that shape the coastline
Split into weathering and mass movement |
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Physical weathering: Freeze-thaw
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Water percolates into cracks of cliff, then freezes to form ice. When the water freezes it expands by 9%, forcing crack to widen
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Physical weathering: Exfoliation
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Due to extreme weather. Surface of rock heats up, but core stays cool. Top layer expands and difference in temperatures causes top layer to crumble off
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Physical weathering: Salt crystalisation
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Salt water evaporates leaving salt crystals on rock. Crystals grow larger over time and this exerts stress on the rock and causes it to break apark. Salt can also corrode rock
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Physical weathering: Wetting and drying
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Clay rich rocks like shale expand when they get wet, and contract when they dry. This causes them to crack and break up
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Chemical weathering: Carbonation
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The dissolving of calcium carbonate from rocks such as limestone and chalk. When it absorbs co2 from the air, the water forms a carbonic acid, which reacts with the calcium carbonate to form calcium bicarbonate which is easily dissolved
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Biological weathering: shellfish
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Specially adapted so they can drill into rocks or some secrete acids
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Biological weathering: sea weed
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Roots attatch to rock and the sea eventually prises away the loose rock. Roots can then grow into small cracks and widen cracks
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Biological weathering: Algae
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Algae lines rock with acidic layer which promotes solution
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Mass movement: Rockfall
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Rock fragments fall of cliff face- usually due to freeze-thaw or undercutting
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Mass movement: Landslides
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Detached slabs of rock fall down a slide plane quickly. Cliffs are often made of softer rock or deposited material, which slips when wet
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Mass movement: Rotational slumping
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Softer materials that overlie more resistant materials are lubricated, causing the whole section of rock to move downwards
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Mass movement: mudflow
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Heavy rain saturates soil and causes it to flow downhill
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