Why does north africa contain a number of large deserts?

Some deserts are found on the western edges of continents. They are caused by cold ocean currents, which run along the coast. They cool the air and make it harder for the air to hold moisture. Most moisture falls as rain before it reaches the land, eg the Namib Desert in Africa.

Explanation:

Around 5,500 years ago, there was a sudden shift in climate in northern Africa leading to rapid acidification of the area. So the tropical and wet environment suddenly turned into a desert.

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