Before and After 
In the before ( on the right ) it shows sand dunes on top of rock underneath the surface with a river in the middle of the valley. After a time the wind erodes at the rock and at the sand. In the after ( on the left ) The sand had been blow off of the rock and the sand dune had gotten smaller. As the sand went down the rock it went into the river and made it into a stream. The wind erosion had made a ventifact which is a oddly shaped piece of rock formed by wind erosion, a loess which is a cliff with jagged edges created by wind erosion. It also eroded at the rock underneath causing it to get smaller and causing the sand on top to go away leaving the rock underneath.
