Geography ~ Sand Dunes


Sand Dune Formation

  • Needs a large sediment supply
  • Large tidal range - a lot os f sand exposed to the wind
  • String and continuos winds needed
  • Sand grains transported via saltation
  • Debris blocks wind - thus, depositon of sediment
  • Embryo dunes form once sediment has completly surrounded the debris
  • Pioneer species (plants) grow and binds the sand together 
  • Vegetation also traps sand - helping the dunes to grow

Embryo Dunes

  • Smallest dunes
  • They're the shadow of the debris
  • Pioneer species bind sand together (Example; Prickly Saltwort)
  • High pH (~ 8 - 8.5) because marine shells are made of calcite / calcium carbonate (Alkaline)
  • pH limits plant growth
  • Salinity limits plant growth - no fresh water
  • Plants need long roots to reach the water table; Long roots stablizes the dune further
  • Plants have to be halophytic (salt tolerant)

Foredunes / Yellow Dunes

  • Found behind Embryo dunes
  • Composed mainly of sand
  • Also known as yellow dunes (due to color)
  • Relatively un-compacted 


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