Sand dunes Conditions for formation: 1. Strong on-shore winds. 2. Large expanses of dry sand (spits, cuspate forelands, bays). 3. Obstacles to limit sand movement.Sand movement (saltation): Is helped or hindered by: 1. Wind velocity. 2. Grain size and shape. 3. Dampness of sand. 4. An obstacle present around which deposition of sand occurs and vegetation grows.
Sand ripples develop which increase deposition Salt tolerant grasses stabilize the sand and creates and obstacle around which wind must pass This turbulence cause sand to be deposited on sheltered side of dune Marram grass has long roots which stabilise the larger dunes
Name: Characteristics: Embryo dune The first part of the dune to develop. Stabilisation occurs via marram and lyme grass, which act as traps for sand. Conditions are dry and plants adapt to this via long roots. Yellow dune Colour is due to a lack of humus, but with distance inland they become increasingly grey due to greater amounts of humus. Heights can reach 5m. Fixed grey dunes Limited growth due to distance from beach. Far more stable as shown by existence of thistle, evening primrose, bracken, bramble and heather. Dune slacks Depressions between dune ridges, which will be damp in summer and water-filled in winter. Species include water mint, rushes, and weeping-willow. Blow outs Often evidence of over use by humans. Large ‘holes’ that appear in the dunes. SAND DUNE CHARACTERISTICS