On the Formation of Sand-Dunes

Booming Sand Dunes

Booming” sand dunes have a remarkable capacity to produce sounds that are comparable with those from a stringed instrument. This phenomenon, in which sound is generated after an avalanching of sand along the slip face of a dune, has been known for centuries and occurs in at least 40 sites around the world. A spectral analysis of the sound shows a dominant frequency between 70 and 110 Hz, as wel...

Sand Dunes on Mars and on Earth

Great Sand Dunes

Endemic species are those that exist at only one location or area on Earth. They tend to be more numerous in habitats that are distinctly different from the surrounding areas. The Great Sand Dunes harbor at least seven endemic species of insects. Many of the insects here are ‘sand obligates’, meaning that they are adapted uniquely for sandy habitats. Currently, just over 1,000 different kinds o...

Biogenic crust dynamics on sand dunes.

Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in model studies of dune dynamics. Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fix...

Minimal model for sand dunes.

We propose a minimal model for aeolian sand dunes. It combines an analytical description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The model provides a qualitative understanding of important features of real dunes, such as their longitudinal shape and aspect ratio, the formation of a slip face, th...