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 ...

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 ...