Discuss the factors that contribute in the formation of deserts. (200 Words)
Desert refers to the regions having a little precipitation (below 25 cm annually) and consequently hostile conditions for survival of plant and animal life. Deserts can be hot and arid, semi-arid, coastal and cold and can be in plains or in mountains. The formation of deserts is a long evolutionary process with agents like wind and water playing an important part.
- Wind pattern. Most of the deserts are located within 15 to 30° north and south of the equator. Here the trade winds blow offshore. The equatorial winds that rose upwards from equator and when they descend at the tropics, they have little moisture. Example: Sahara desert.
- Presence of cold currents. Most of the hot deserts are present along the West Coast of continents as cold ocean currents along these coasts have a desiccating effect on rainfall over interior areas. Example: Atacama Desert.
- Presence on the leeward side also causes little precipitation. It is also called as Rain Shadow desert. Example: Gobi desert. Also absence of mountain to cause orographic rain is also a cause. For example Aravalli is not able to cause rainfall and consequently we have Thar.
- Polar areas have very cold air which does not cause precipitation frequently. So they are also considered as cold desert.
- The formation of deserts is caused also due to weathering process. Winds can blow freely in desert areas due to little vegetation and cause abrasion effects. Temperature variations of hot days and cool nights have an exfoliating effect on the outer surfaces. Occasional downpour also causes weathering as water expands on being frozen. All of these cause faster disintegration of rocks and particles are transported and deposited in sand dunes.
Desertification is on the rise in the world as a consequence of climate change and human activities and steps need to be taken to check this.