Coasts Revision Notes - AQA Geography

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Coasts Revision Notes – AQA Geography

  1. Spring and Neap Tides

Spring tides occur when the Earth, Sun and the Moon are all about in the same line.  This causes the highest tidal range due to the strongest gravitational pulls with the high tides being 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 lowest tidal range of tides.

  1. Coastal Transport

Long shore drift transports material along the coast. In the UK, the prevailing wind blows from the South West 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. Lighter 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.

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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 (around £5,000 per groyne and are unasthecially pleasing) yet they do trap the sand.

  1. Headland Formation

Headland formation occurs when the bands rock type run perpendicular to the coast – this is known as a discordant coastline. The coast has alternating bands of resistant (hard) and less resistant (soft) rock – these types of rocks erode at different rates.

The less resistant rock are eroded at a faster rate (through ...

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