The western Sahara is an area of rock-strewn plains and sand deserts of varying elevation. The land is almost entirely without rainfall or surface water but possesses a number of underground rivers that flow from the Atlas and other mountains. The soil of this region of the Sahara is fertile and, where irrigation is possible, produces excellent crops. Although rainfall is scanty in the area, a number of the central Saharan peaks are snowcapped during part of the year. The Libyan Desert is considered the most arid part of the Sahara.
Moisture is almost totally absent and few oases exist.
The valley of the Nile River and the mountainous area of the Nubian Desert to the east of the Nile are, geographically, part of the Sahara, but the irrigation afforded by the Nile transforms the desert into fertile agricultural land throughout much of Egypt. In Egypt and Algeria, limited areas, such as the Qattara Depression, are below sea level. Except in the oases the desert is almost devoid of vegetation, although some stunted, thorny shrubs grow in the western Sahara. The chief trees of the oases are the date palm and a form of acacia. Gazelle and antelope are found in many parts of the desert, as are jackal, fox, badger, and hyena.