Friday, 15 March 2013

Coastal Spits and Bars!

Longshore Drift occurs when prevailing winds transport sediment along a beach.

This results in a Spit, which is a long narrow piece of sand/shingle which sticks out into the sea/an estuary.

Bar (or a barrier island) may form where there are changes to coastal direction but no estuary to break the sequence of sedimentation.

The 2 ends of a spit are...

  1. The Proximal End - end nearest to the shore/land
  2. The Distal End - end furthest away from the shore/land
Doesn’t Grow...
-Secondary winds also shape the spit
-Wave refraction
-A river’s current may stop deposition across the entire estuary
-The river channel may be too deep, or the water may flow too fast
  1. Sediment is carried by Longshore drift
  2. Shingle (larger sediment) is deposited behind the headland
  3. Storm waves move sediment above the high water mark making the feature more prominent
  4. Finer material is carried to the end of the spit
  5. Sand dunes may form as the sand dries and is blown around at low tide which stabilizes the spit
  6. Waves and rivers deposit sand and mud which makes salt marsh


Spurn Head in Humberside is 6km long, 15m hig, and 150m wide

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