You’d be surprised to know that most of the deserts are found on the western margin of the continents. When we look at the physical map of the world, we would see the majority of the deserts on the Western margins on the continents, either along the coast or the interiors. The two Geographical factors responsible for this are:
1. Cold Current (West Wind Drift)
The west wind drift, which travels parallel to the latitudes over the Atlantic, carries cold water and travels along the Arctic, Indian and Pacific oceans. On its journey to the east, it gets in proximity with the continents and then drains the western part of every continent it comes in contact with. The cold oceanic current drains the continents of Africa, Australia, and South America and forms the Namib, Great Western Desert, and Atacama deserts, respectively.
So, what is the reason for the development of deserts in these regions? When the cold air mass brought by the cold current comes in contact with the warm air on the landmass, cold air replaces the warm air as it has more density than warm air. This results in a cool, stable coastal atmosphere. The activity of evaporation in the ocean will be reduced and produces extremely low rainfall over the coastal deserts and hence forms one of the driest ecosystems of the world.
2. Trade Winds
We all know that the earth rotates from west to east. Because of the rotation of the earth, we come in contact with coriolis force. Due to coriolis force, the Trade Winds coming from North of the Equator deflects towards right and Southern towards left. Most of the Northern Hemisphere comprises land and only North-Eastern Trade Wind’s effect on the formation of the desert. This Trade Wind on its journey to the west carries dry winds.
Dry winds are formed because the wind flows from arid (High) temperature regions. The dry winds blow off the cloud cover on the western margins, allowing the sun rays to fall directly on the land. The Australian deserts, Sahara desert, and Kalahari desert on the western margins of Australia and Africa are some examples of these deserts. As we know, a land without cloud cover causes no evaporation and hence no rainfall.
Therefore, deserts formed by cold currents are also called Coastal deserts, while the deserts formed by Trade winds are called Trade wind deserts. Even though the formation of these deserts is different, the qualities of them are the same. All deserts are arid with less vegetation and less rainfall.
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