Why is there a large desert (the Sahara) in North Africa?

Answer 1

Are we doing your homework for you right now, because you're asking a lot of geology questions that are already in the text books.

Answer 2

The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last ice age, the Sahara was bigger than it is today, extending south beyond its current boundaries[2]. The end of the ice age brought wetter times to the Sahara, from about 8000 BCE to 6000 BCE, perhaps due to low pressure areas over the collapsing ice sheets to the north[3].

Once the ice sheets were gone, the northern part of the Sahara dried out. However, not long after the end of the ice sheets, the monsoon which currently brings rain to the Sahel came further north and counteracted the drying trend in the southern Sahara. The monsoon in Africa (and elsewhere) is due to heating during the summer. Air over land becomes warmer and rises, pulling cool wet air in from the ocean. This causes rain. So, paradoxically, the Sahara was wetter when it received more insolation in the summer. In turn, changes in solar insolation are caused by changes in the Earth's orbital parameters.

By around 2500 BCE, the monsoon retreated south to approximately where it is today[4], leading to the desertification of the Sahara. The Sahara is currently as dry as it was about 13,000 years ago.[5]

You could get more information from the link below...

Answer 3

There are deserts throughout the world in those latitudes, both Northern and Southern Hemisphere. The Sahara just happens to be the largest. For instance Southern Africa has the Kalahari and the Namib in similar latitude. America has the desert states and of course most of Mexico, and in South America there is the Atacama, which is a coastal desert in the same latitude as Africa's equivalent, the Namib desert.

It is to do with wind circulation. Those latitudes receive very little rain-bearing winds.