Coasts Revision Notes – AQA Geography
- 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.
- 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.
