Creating Sand DunesThere are five main steps to creating sand dunes: A strong sea breeze blowing inland will pick up the grains of sand and will move them to the beach. This happens when the tide goes out and the beach sand dries. The grain of sand will continue to move with the wind and will not stop until there is something in its path. At the top of the beach is usually a shoreline made up of seaweed and trash left behind by the tide. The grains of sand jump over this shoreline and accumulate where the calm air is behind them. This creates a small embryonic dune. The dune can easily be destroyed unless it is colonized by plants. Quackgrass is the most common plant that can grow on dry, salty sand. The sand is then bound together using the long spreading roots of the seagrass. The dune will grow as more and more sand is trapped. The marram grass will then colonize the dune and replace the seagrass once the dune has reached approximately one meter in height. It is not difficult for the marram grass to obtain water because its long roots are fifteen to twenty meters long. This becomes a superb sand trap and the marram covered dunes can grow in height by a meter per year. A dune ten to twenty meters high is called a yellow dune, and it is possible for a new dune embryo to form in front of it. Conditions behind the dune become less windy and less sand instantly accumulates behind it once the yellow dune is completed. measures approximately ten meters high. When the marram grass dies, it decomposes on the dune, adding humus to the sand. The combination of humus and sand forms soil in which other plants can grow. These can include dandelions and retharrows. This type of dune is called a semi-fixed dune. Soil depth increases with time and so does soil.