Tides: coastal processes

• What are tides caused by

  the gravitational pull of the moon and sun ( the moon has much greater influence bc it's nearer)
• What are spring tides

  Large bulges of water = spring tides

  
  

  Gravitational pull of sun and moon are combined (sun,moon and earth all align) = highest high tide, lowest low tide, and max tidal range

  - happen every 14 to 17 days so twice a month

  - spring equinox = 20th March
• What are neap tides

  Small bulges of water = neap tides

  
  

  Sun and moon are at a right angle to each other

  Gravitational pull of sun and moon counteract each other = lowest high tides, highest low tides so low tidal range

  - Happen every 14- 17 days so twice a month

  - autumn equinox = 22nd September
• What can tidal ranges be classified into

  - Macrotidal = more than 4m

  - mesotidal = 2 to 4 m

  - microtidal = less than 2m
• When do tidal surges occur

  Large tidal range occurs in areas with narrowing areas of seawater such as English channel where water from Atlantic and North Sea 'piles up' confining to an narrow neck
• Example of tidal surges

  In narrow estuaries the effect can be more obvious when the tide rises in Bristol Channel it's increasingly confined into the narrowing Severn estuary and a tidal range of 13m is experienced
• What is a high energy coastline?

  A coastline, where strong prevailing wind creates high energy waves, and the rate of erosion is greater than the rate of the deposition
• What is a low energy coastline?

  A coastline where wave energy is low, and the rate of deposition is often greater than the rate of erosion
• What is the tidal bore

  Is a wall of water that surges up river with the advancing high tide