Gusty wind blowing in the desert drives billions of particles of sand before it. There are hardly any obstacles before the blowing wind in a plain desert but sooner or later some tufts of vegetation or the outcrops of rock come in its way. Sometimes sand-dunes apply brakes on the wind speed. Blasts of wind then lose their force and the particles of sand start settling down on the ground. These particles first settle in a row parallel to the obstacle. As more sand settles little row becomes a ridge and in turn becomes an obstacle to the wind. The resistance of obstacle is felt mainly by the newly blown particles. These newly arrived particles of sand rebound a little after colliding with the first parallel ridge of sand. They roll back a little and settling down start forming a new ridge parallel to the first one. Both the ridges of sand become almost parallel because particles of sand being identical in size cover the same distance when rebounded. After some more time as the second ridge grows it becomes an obstacle to wind and a third parallel ridge starts forming in front of it. Ultimately a beautiful landscape of ripples forms in desert.
A noteworthy point: In order to prevent the desert from advancing further, trees and scrubs having spreading foliage should be planted along the edge of the sandy ground to serve as wind-breakers. After having effectively raised the first row of the greenbelt, other rows will be formed by natural growth of more trees and vegetation to prevent further expansion of the desert.