Question

how did sahara desert became desert?

Answer 1

The Sahara desert was actually an ocean (Oceanus Saharus ) millions of years back. It had a thriving flora and fauna of a forest as confirmed by the fossils found there. The evidences found in the Cave paintings in Sahara desert suggest that there once used to be rivers with crocodiles and other water living creatures. Elephants, lions, giraffes, ostriches, sheep, cattle and goats were common animals.
The turning of ocean into present day desert is believed to be due to the movement of tectonic plates under Africa and Asia. This movement caused drastic change in climate, making it a very hot and dry region.