Deserts of Africa

The Sahara is the largest desert in the world. Bordered in the west by the Atlantic Ocean, in the north by the Atlas Mountains and Mediterranean Sea, in the east by the Red Sea, and in the south by a semiarid transitional region called the Sahel, it fills nearly all of northern Africa: a total area of 3,320,000 square miles. Although it covers a huge area, its actual area varies over time as the desert expands and contracts. The Sahara has a diverse topography consisting of shallow basins and depressions; sand sheets, dunes, and sand seas; lakes; abrupt mountains; and plains and plateaus covered in gravel or small rocks. The soil is mostly saline rich, so salt-tolerant plants do well there. You can also find scattered concentrations of grasses and small heat-tolerant shrubbery, but for the most part, the Sahara is generally sparse. A recent discovery of dune deposits suggests that the Sahara is at least seven million years old.

The Kalahari Desert

The Kalahari Desert is small compared to the Sahara, but it still covers nearly 360,000 square miles of the interior plateau of Southern Africa. It covers nearly all of Botswana, the eastern third of Namibia, and the northernmost part of the South African province, Northern Cape. The Kalahari is mainly a sand-covered plain made up of sand sheets, dunes, and dry lakes, caused by wind over the years. The northeastern part of the Kalahari actually receives on average more than twenty inches of rain per year, thanks to the Indian Ocean; yet, the water immediately drains into the deep sand seas, leaving no surface water. This lack of surface water makes this part of the Kalahari technically a desert. The southern Kalahari is almost completely devoid of vegetation, except areas in the dry lakes where salt content is low and sturdy grasses grow after a rain. The northeastern Kalahari, though, has lush vegetation, including woodlands, palm trees, and forests of evergreen and deciduous trees, as a result of the additional precipitation.