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 
• …