Pediplain (from the Lat. pes, genitive case pedis - foot, foot and Eng. plain - plain) - the extensive slightly inclined denudation plain, which is formed under the conditions of arid and semiarid climate on the spot is earlier than the existed mountain or hilly relief by the parallel retreat of slopes from the axis of valleys and connection of the separate vyrovnennykh sections - pediments. Relative to the mechanism of the formation of pediplena there is no unanimous opinion. It is considered that the main and necessary condition of forming pediplena is the long absence of the motions, which create inclines, and the fixed attitude of the basis of denudation, which determines the descending development of relief and levelling off under any climatic conditions. It is formed by the erosional works of wind.Mountains are made up of both hard and soft rocks. During erosion by wind , soft rocks are washed out, but harder rocks remained in their place. they formed some uplands and are called 'Inselberg'.