sand dunes

• beaches 


  deposits of sand and shingle at a coast
• pebble beaches 


  when waves wash away the fine sand and leave behind the pebbles
• development of dunes


  1. embryo dunes form around deposited obstacle - logs
  2. these develop an become stabilised by vegetation to form foredunes and tall yellow dunes. marram grass is adapted to the windy, exposed conditions - it has very long roots to find water - these long roots bind the sand and stabilise the dunes
  3. in time, rotting vegetation adds organic matter to the sand making it more fertile - a much greater range of plants grow in the 'back' dunes
  4. wind can form dunes depressions in the sand called dune slacks which ponds can form in