full-size image (26 kb)

A simple crescent-shaped (barchan) dune, looking southwest

• Which way does the wind blow to cause the migration of this dune?
  
  
• Look at the full-sized image, and notice the presence of smaller scale wind ripples, both on top of the dune, and at the foot of the dune. The wind direction indicated by these ripples is different from that for the dune as a whole. How can you explain this?

• Think about this, then go to explanation.

Scale: The dune is about 2 metres high.

Grid reference: southwest from 868 301