Tropical deserts and subtropics
Tropical deserts cover about 30 % of Africa. The Sahara is the largest hot desert in the world (area about 9.2 million km²; the textbook gives 7.8 million km²); annual rainfall is up to 100 mm, and in the interior it sometimes does not rain for several years. The daily temperature range is large: +40–50 °C by day and down to 0 °C at night; so rocks crack and stony deserts (hamada) form. Sandy deserts have barchan dunes; in the centre residual mountains rise, such as Tibesti (3 415 m), Darfur (3 088 m) and Ahaggar (2 918 m). Plants are very scarce: wormwood, saxaul, acacia, and in the Namib the rare welwitschia; in oases the date palm is the main tree. Semi-deserts have succulents, aloe and wild watermelon. Animals are adapted to the desert: antelopes, jackals, foxes, camels, lizards, tortoises. The subtropical zone lies in the north-west (Atlas) and south-west (Cape region): evergreen hard-leaved forests and shrubs — olive, cork oak, Atlas cedar; above 3 000 m in the Atlas it snows in winter. Animals include the hyrax, the tailless macaque, jackals, wild cats and rodents.
“Surviving the desert”: groups prepare a poster explaining how the camel, lizard, date palm and welwitschia adapt to desert conditions.