The illustration gives information on how a particular type of desert called a rain-shadow desert comes into existence.
At a glance, this formation process involves seven stages, including the moist air that had blown over the sea rising up a mountain, the water vapour falling down as rain, the dry air going down to the other side of the mountain, and eventually the dry wind reaching inland and creating a desert. In addition, the base of the mountains in the wind’s route stretches across thousands of kilometres.
As regards the first, on the windward side, the winds from the sea surface approach the coast and then are pushed uphill when they hit a mountain. Next, near the halfway of their journey to the mountain top, this moist air continues rising and faces a decrease in temperature. This leads to the formation of clouds, and once they are above the top of the mountain, rain falls down.
The final two stages happen on the other side of the mountain – the leeward side, and the sixth stage is concerned with the dry air continuing over the mountain, followed by the final stage where dry winds arrive at inland areas, resulting in a rain-shadow desert.