![]() ![]() ![]() Such types of shallow lakes are called playas where water is retained only for a short duration due to evaporation and quite often the playas contain good deposition of salts. In times of sufficient water, this plain is covered up by a shallow water body. In basins with mountains and hills around and along, the drainage is towards the centre of the basin, and due to gradual deposition of sediment from basin margins, a nearly level plain forms at the centre of the basin. Plains are by far the most prominent landforms in the deserts. That’s how the high relief in desert areas is reduced to low featureless plains called pediplains. So, through parallel retreat of slopes, the pediments extend backward at the expense of the mountain front, and gradually, the mountain gets reduced leaving an inselberg which is a remnant of the mountain. This method of erosion is termed a parallel retreat of slopes through backwashing. Once, pediments are formed with a steep wash slope followed by a cliff or free face above it, the steep wash slope and free face retreat backward. Such rocky floors form through the erosion of the mountain front through a combination of lateral erosion by streams and sheet flooding.Įrosion starts along the steep margins of the landmass or the steep sides of the tectonically controlled steep incision feature over the landmass. Gently inclined rocky floors close to the mountains at their foot with or without a thin cover of debris are called pediments. Pediments and Pediplains Landscape evolution in deserts are primarily concerned with the formation and extension of pediments. Stream channels in desert areas are broad, smooth, and indefinite and flow for a brief time after rains. The wind moves fine materials and general mass erosion is accomplished mainly through sheet floods or sheet wash. That means the weathered debris in deserts is moved by not only wind but also by rain/sheet wash. The desert rocks devoid of vegetation, exposed to mechanical and chemical weathering processes due to drastic diurnal temperature changes, decay faster and the torrential rains help in removing the weathered materials easily. Though rain is scarce in deserts, it comes down torrentially in a short period of time. In fact, many features of deserts owe their formation to mass wasting and running water as sheet floods. The wind action creates a number of interesting erosional and depositional features in the deserts. The impact is simply the sheer force of momentum which occurs when sand is blown into or against a rock surface. In the transportation process sand and silt act as effective tools to abrade the land surface. ![]() Deflation includes lifting and removal of dust and smaller particles from the surface of rocks. Winds cause deflation, abrasion, and impact. Of course, there are storm winds that are very destructive. Winds also move along the desert floors with great speed and the obstructions in their path create turbulence. The heated floors heat up the air directly above them and result in upward movements in the hot lighter air with turbulence, and any obstructions in its path set up eddies, whirlwinds, updrafts, and downdrafts. The desert floors get heated up too much and too quickly because of are dry and barren. The wind is one of the two dominant agents in hot deserts. ![]()
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