Sand dunes are large hills of sand formed by the wind. They are commonly found in deserts and along coastlines, where loose sand is abundant. The shape and size of sand dunes can vary greatly, depending on factors like wind direction and the amount of sand available. Some dunes can reach heights of over 500 feet, while others may be just a few feet tall. These natural formations play an important role in the ecosystem. They help protect coastal areas from erosion and provide habitats for various plants and animals. Additionally, sand dunes can store water and support unique vegetation, making them vital for maintaining biodiversity in their environments.