Give me some features of sand dunes ??? : )
Answers
Sand dunes are a natural wonder with beauty and majesty all their own. However, when you know more about the dunes, they take on even greater significance. Once you learn about the complex, dynamic dune ecosystem, you will appreciate dunes even more. Before we describe sand dunes, we need to know what sand is. Sand is considered any loose, granular material having grains which are 0.05 to 2.0 millimeters in diameter. The designation "sand" does not refer to how the material was formed or what it is made of. Sand can, and does, come from all three major rock types: igneous, metamorphic, and sedimentary. Sand can be primarily one mineral or material, or it can be a mixture.
Sand dunes are mounds of windblown sand which vary greatly in size, from less than one meter to tens of meters high. The size depends upon the supply of sand. There is even greater variation in the area covered by dunes. Many of the more recognizable dune forms are ridges or complexes of mounds or crescents. The shape of individual dunes is equally variable. Shape relates to the direction and strength of the wind forming it, as well as to the amount of sand available. The impressive sand dunes along the eastern shore of Lake Michigan were created by the prevailing westerly winds blowing the sand deposited along the beaches into the dune formations.