Coasts Revision Notes – AQA Geography

1. bound and Neap Tides Spring vs. Neap TidesSpring tides occur when the Earth, Sun and the Moon ar all about in the same line. This causes the highest tidal range due to the strongest gravitational pulls with the high tides cosmos the largest and the low tides being the smallest.Neap tides occur when the Earth, Sun and Moon are at 90 degrees which causes the gravitational pull to be less effective. This produces the utmost tidal range of tides.1. Coastal TransportLong shore sick transports material along the coast. In the UK, the prevailing wind blows from the South westward causing the waves to approach the southern coast at an angle of 45 degrees. Therefore material moves from the west to the east.The swash of the wave carries the material up to the beach at this angle. The bed load is moved along by rolling by traction however pebbles are lifted and bounced along the floor in a leap frog action this is saltation. igniter material is carried by suspension (such as grains of sand) and weak acids (e.g. carbonic acid from precipitation) may act on soluble rocks (carbonate rocks e.g. limestone) and move the material in solution.The backwash carries the material at 90 degrees- causing a zig-zag motion. Groynes may be in place to reduce this however they can be expensive ( somewhat 5,000 per groyne and are unasthecially pleasing) yet they do trap the sand.1. question FormationHeadland melodyation occurs when the bands rock type run upright to the coast this is known as a discordant coastline. The coast has alternate bands of resistant (hard) and less resistant ( haywire) rock these types of rocks erode at contrary rates.The less resistant rock are eroded at a faster rate (through the processes of hydraulic action, abrasion and corrosion) and the more resistant rock erodes at a slower rate and protrudes out into the sea.Wave divagationNow the school principal is protruding out into the sea, this receives high energy waves. When the waves assum e the coastline, they are refracted and they tend to bend round the headland, into lower energy waves. These waves therefore deposit sediment and beaches eventually build up.Case Study Purbeck coast, Dorset. The eastern side is discordant.Headland The foreland Purbeck Coast, Dorest. Geology Chalk (made millions of years ago from Coccoliths). This headland is 1.3km wide.Bay Swanage Bay made from Wealden & Purbeck bed cadavers. This bay is 2.5 km wide.1. Causes of driblet collapseCoastal Reasons* When waves head towards the coastline and the sea gets shallower, friction in the bed slows the bottom of the waves and make them more elliptical. The crest of the wave rises and so it collapses.* Destructive waves are high frequency, and are high and deep. They are around 10-14 waves per minute and their strong backwash removes material.* The waves break at the base of the drib where the wave energy is concentrated.* This part of the cliff experiences rapid erosion constitutiona l abrasion, where material carried by the waves (eg rocks) are hurled against it. Also, H.A where the extort of the air in the cracks from the pee compress and release which erodes it.* This forms a wave publish liberty chit* everywhere time, under the force of gravity, the mass above the wave cut notch cannot hold and collapses.* This processes of collapsing continues and the cliff retreats back.* This then leaves behind a wave cut platform that is no more than 5 degrees at the Low pissing Mark.* As the platform gets longer, the waves have to reach further and many take apart reducing the rate of erosion.* Sub Arial processes erode the platform such as paddock and seaweed.* Case Study Broad bench Dorset, cliff is mixture of clay and shale (headlands made of Portland stone). Extension is 200m of platform, height of cliff is 20 m. Part of Jurassic coast world heritage site.Sub-Arial* Not directly linked to sea, only from land* Freeze Thaw When the diurnal range is around 0 dregrees Scottish Highlands Water expands by around 9%. Fluccutations in pressure fragments of rock may break off.* Biological Rabbits may burrow into the cliff and piddocks may also weaken the rock which may remove some of the rock.* Chemical live oning, CO2 found in rainwater may form carbonic acid when it rains attacks the calcium carbonate such as in limestone.Mass Movement* Slumping Rainfall infiltrates the soil, making it heaver.* The material moves downhill, leaving a exposed scarp face* Case Study Holbeck Hall, Scarborough.* 1993 ironical weather cracked the clay. This made the rock impermeable due to hot dry conditions* Next two months 140mm of rain fell (prolonged rainfall)* This then therefore infiltrated the soft rock above, but lubricated the clay.* On 3rd of June the land was slip into sea at 3m per hour. Collapse of hotel. Rest of hotel had to be demolished and they owners sued the permission breach of its duty and care.