Question

what causes the drought cycles in africa

Answer 1

There's no singular reason. The main one, however, is that the water dries up too quickly.

The newest one that is starving children in Africa and devastating the Horn of Africa, however, is thought to have occurred because of the El Nina year.

‘What we do know is that La Niña started to develop in August 2010. It cools surface waters in the central and eastern Pacific Ocean, while allowing warmer water to build in the eastern Pacific. “The pool of warm water in the east intensifies rains in Australia, the Philippines, and Indonesia. Domino-style, this pattern also increases the intensity of westerly winds over the Indian Ocean, pulling moisture away from east Africa toward Indonesia and Australia. The result? Drought over most of east Africa and floods and lush vegetation in Australia and other parts of Southeast Asia,”

-US National Aeronautics and Space Administration

This means, essentially, that El Nino pulls away humidity from Africa. Because of this the water evaporates much faster. It the floods you're going to hear a lot about in the news pretty soon.

Answer 2

Hi, before you zero in on Africa, first ensure that you understand what a drought exactly is ( http://en.wikipedia.org/wiki/Drought), there are many different types of drought although all may point in general to the moisture in the soil. It is important to differentiate drought and aridity , what you see in Sahara desert, Atacama or Death valley is aridity and not drought. This is a fundamental point that should be understood before trying to understand the severity of drought.