Abstract Aeolian processes, involving erosion, transportation, and deposition of sediment by the wind, occur in a variety of environments, including the coastal zone, cold and hot deserts, and agricultural fields. Common features of these environments are a sparse or nonexistent vegetation cover, a supply of fine sediment (clay, silt, and sand), and strong winds. Aeolian processes are responsible for the emission and/or mobilization of dust and the formation of areas of sand dunes. They largely depend on other geologic agents, such as rivers and waves, to supply sediment for transport. Areas of sand dunes occur in inland and coastal settings, where they often provide a distinctive environment that provides habitats for endemic and rare or threatened species. In both coastal and inland settings, dune migration and sand encroachment may impact neighboring ecosystems and resources, as well as infrastructure. Transport of fine sediment by wind may cause dust storms, events in which visibility is reduced to less than 1 km by blowing dust. Dust storms impact air quality in their immediate vicinity as well as in areas downwind. Deposition of dust may have a significant effect on the composition and nature of soils in arid regions and beyond. Far-traveled dust from distant sources may have a significant effect on soil chemistry and nutrient status (e.g., Farmer, 1993 ).

Eolian sands tend to be fine grained and quartz rich. This mineralogical maturation may be attributed to mechanical breakdown of sand-size feldspar grains and their subsequent winnowing from dune fields. During eolian transport, ballistic impacts between saltating grains and stationary grains on the ground are very common. If the impact is sufficiently strong, the collision may be inelastic and part of the kinetic energy of the incident grain may be dissipated through inelastic deformation and subsequent breakdown of the grains involved in the collision. The theoretical calculation presented in this chapter indicate that the mechanical breakdown of feldspar sand grains through ballistic impact can be achieved if wind speed exceeds 10 m·s −1 . Therefore, quartz-rich sand can result from ballistic impacts between sand grains in deserts.