Sand dunes in the Sahara desert in Africa. The Sahara Desert is the world ... Aswan Dam, across the river Nile in Egypt, is the world's largest embankment dam. A dam is a barrier that blocks ...

Africa has nine deserts ... local communities. The desert’s only permanent river is the Nile, which flows across its northeastern edge. Incredibly, the Sahara wasn’t always barren.

Paleoclimate and archaeological evidence tells us that, 11,000-5,000 years ago, the Earth's slow orbital 'wobble' transformed today's Sahara desert ... East Africa (Figure 3). The Nile River ...