All these answers can be found in the deserts pages (see left hand menu).

1. One-third of the Earth's surface is covered by desert.

2. To be classified as desert, there must be less than 100mm of rainfall annually.

3.  Aproximately 20 per cent of our desert areas are sandy. Other larger areas of desert are covered in rocks and gravel.

4. The most arid continent on Earth is Australia.

5. The Nile and Niger rivers both cross the Sahara desert.

6.  The euphorbia is a cactus-like plant that grows in African deserts.

7. Camels can drink water weighing a quarter of their body weight.

8. 1200 species of plant can be found in the Sahara desert.