The diagram illustrates the process by which a rain-shadow desert is formed near a mountain range.

At the beginning of the process, winds approach the coast from the sea, carrying moist air towards the mountains. When these winds reach the mountain slopes, they are forced upwards. As the air rises, it cools, which causes clouds to form on the windward side. Eventually, the moisture in these clouds falls as rain, mainly over the mountains and the coastal side.

After the air has passed over the mountain peak, it contains much less moisture. This dry air then moves down the leeward side and continues travelling inland. As a result, very little rainfall reaches the land beyond the mountains. Over thousands of kilometres, these dry winds create extremely arid conditions, and this inland area gradually becomes a rain-shadow desert.

Overall, the desert develops because moist air from the sea loses its water on the windward side of the mountains, leaving dry air to continue inland on the leeward side. (167 words)