Sand grains from both sources range in size from 0.2 mm to 2 mm. The dune shapes you see today would likely be what you would see if you visited next year, in 10 years, and even 100 years from now. There is a great deal of sand movement with each wind storm, but moisture in the dunes seems to have a stabilizing effect, maintaining the height, contours and shape of the sand in the main dune mass. If you were to dig down into the sand, generally within 8-10 inches, you would find moist sand. Saltation is a process where the sand grains bounce as they are transported by wind.
Suspension involves movement of sand grains when sand is blown high into the air.
Southwest winds funnel through three low mountain passes in the Sangre de Cristo Mountain range. The northern most pass and highest pass is Music Pass . It is located out of view behind Mount Herard, the flat-topped mountain to the north of the dunes. Because of its height and location, Music Pass probably has the least effect on the dunes. Medano Pass is the middle pass, visible in front and to the right of Mt. Herard.