Desertification in sub-saharan africa is mainly caused by

Natural causes.

Explanation:

Most of them are the natural cases like the poor soil fertility, deforestation, and overgrazing by animals, drought is one of the natural calamities that affect the lands most and is climatic variation and increase of the human actives, the vulnerability of the ecosystem and the semi-arid and arid soil.

Answermost of the time it would be ground into fine sediment,and sometimes they are carried away from the original location;

Answer// dinosaurs emerged during mesozoic era;