It is a common site at both the beach and in the desert to see sand dunes. Sand dunes are large or hills of sand that are solid enough to stand on, climb up, or even drive over in some cases. They range in size from smaller than a car to as large as a small mountain. Most sand dunes are longer on the side that faces the wind and have a steep drop off on the side not exposed to the wind. So what forms these magnificent sand dunes? Read this article to find out.
How do Sand Dunes Form?
The first stage of a sand dune being formed is the movement of sand. Sand can usually be found around water sources such as rivers, lakes and the oceans, but it can also be found in deserts. When it is wet sand does not move very much at all, but when it is dry it becomes light enough for the wind to pick it up and carry it. Very fine grains of sand can be blown and float through the air. Larger gains of sand tend to bounce along the ground. So the formation of a sand dune starts with the wind blowing the sand.
Next the sand begins to pile up. This may occur because there is a rise in the land around the area, or it gets caught in something such as a rock, stick or even a wet sand mound. The wind continues to blow the sand towards the mound forming the sand dune begins to form as the sand piles up. It keeps piling up until it collapses under its own weight. The sand that has collapsed slides down the side of the pile and comes to rest at the right angle to make the dune stable. It has been observed that this is about a 30-34o angle. The dune slowly migrates in the direction that the wind blows as the sand is continuously blown up the dune face and then slips down the other side called the slip face. As long as there is loose, dry sand the dunes will continue to grow and move.