In addition to an excellent series of books, a dune is a wind-formed mound of sand.
The prevailing winds blow sand up the face of the dune, until it reaches the top and falls onto the lee
) and settles. In this way, the dune advances forward. Dunes come in many shapes and sizes... some may be over a thousand feet tall.. and others are but ripples along a windy beach. Dunes are usually found in desert
s, as most wet areas support vegetation which would stabilize them (in some areas of the Midwest
there are vast forested hills that are actually stabalized dunes). Dunes are also common along beaches where there is a steady supply of sand
. Dunes often take the form of crescent-shaped ridges, with the curve facing downwind. However, depending on the prevailing winds, they may take many forms, including huge mounds or star-shaped formations.
Although appearing lifeless, sand dunes support a variety of life. Many plants, such as sand verbena, are adapted to life in sand dunes. They are xeric, or tolerant of low moisture, and the also usually have tough stems and leaves to ward off sandblasting. These plants also have extensive root systems and are tolerant of becoming exposed by erosion or being buried. Many animals, such as beetles, lizards, snakes, and kangaroo rats, also inhabit sand dunes. Often these species are rare as they are restricted to one dune field.
Sand dunes are found throughout the deserts of the US, especially southwestern Arizona and southeastern California. They are also abundant in other deserts, especially the Sahara. Dunes are also common along beaches, especially those near rivers which supply a constant stream of sediment.