Oasis

Oasis, area in a desert where there is sufficient water for plants to grow. Oases vary in size, from small ponds to vast regions covering thousands of square miles. The Nile Valley, the home of most of Egypt's people, is a large oasis flanked by barren desert. Many oases occur in areas bordering mountain ranges because the rain that falls on the mountains often seeps through porous rock layers under the desert. Oases may also occur around springs where the porous rock comes to the surface, or the water may be tapped through wells. Artificial oases are found in many deserts.