A desert is a barren area of landscape where little precipitation occurs and consequently living conditions are hostile to plant and animal life. In other words, it is extremely dry area of land with sparse vegetation.
The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation (the wearing away of the Earth's surface by moving water, by ice, by wind and by waves, leading to a reduction in elevation and in relief of landforms and of landscapes).
There are four types of desert found in the world: sub-tropical desert; Coastal deserts; Cold desert; Polar Desert. The fifth part of the Earth's surface is desert. They are found in Asia, Australia, Africa, North America and South America. Sahara is the world's largest tropical desert (desert).
Let us know why most of the world’s tropical deserts located on the Western margins of continents?
There are four major factors responsible for the location of the world's tropical desert on the Western margins of continents:
1. Offshore areas of trade wind and falling under the rain shadow area: When the moisture laden trade wind flows from east to west shed their moisture on the eastern part and by the time they reach the western margin, they become dry. These dry winds make the soil more and this led to the formation of the desert.
2. Anticyclonic conditions: The areas between 20 ° -30 ° latitude on western margins of continents are the regions of descending air. Because of this, the air gets compressed and warm as it descends and thus the moisture keeps decreasing.
3. Formation of Rain-shadow Zone: A region in the lee of mountains that receives less rainfall than the region windward of the mountains is called rain-shadow zone.
In the above image, you saw how mountain is acting as a barrier for prevents orographic rainfall. For example: Thar Desert in India is formed due to the formation of rain-shadow zone because Aravallis mountains are situated parallel to the region. Therefore the moisture holding winds pass away from the region because there is absence of mountain barriers.
4. Presence of cold ocean currents along the western coast of continents tends to stabilise the air over the coast. This prevents cloud formation and rainfall. Hence, it leads to arid conditions or the formation of marine deserts on the adjacent coastal lands.