Geological work of wind and its landforms

The geological work of wind is called aeolian action. It is strong in deserts and dry coasts where there is little vegetation, loose sand and strong wind. It has three parts:

1. Erosion
   • Deflation: lifting and removal of loose fine particles.
   • Abrasion (sand blasting): grains carried by wind cut and polish rocks.
   • Attrition: grains wear each other down to rounded, frosted shapes.
2. Transportation: fine dust moves in suspension for long distances; sand moves by saltation (bouncing, the main way) and coarse grains by surface creep.
3. Deposition: when the wind speed falls or hits an obstacle.

Erosional landforms

• Deflation hollows (blowouts): wind lifts loose fine particles and lowers the ground, e.g. Qattara depression.
• Mushroom (pedestal) rocks: sand abrades the base of a rock more than its top.
• Yardangs: streamlined ridges of rock parallel to the wind.
• Ventifacts: pebbles with polished, flat faces cut by sand blast.
• Zeugen: tabular ridges of hard rock over softer layers.
• Desert pavement: gravel left after fine particles are blown away.
• Inselbergs: isolated residual hills.

Depositional landforms

• Sand dunes: barchan (crescent shaped, horns point downwind), transverse, longitudinal (seif) and parabolic dunes.
• Ripple marks: small ridges on sand surfaces.
• Loess: thick deposit of fine, windblown silt, uniform, porous and buff in colour (northern China). It collapses when wetted, which matters in foundation design.