In geography, an oasis (plural: oases) or cienega (southwestern United States)'s an isolated area of vegetation in a desert, typically surrounding a spring or similar water source. Oases also provide habitat for animals and even humans if the area's big enough. The location of oases has been of critical importance for trade and transportation routes in desert areas. Caravans must travel via oases so that supplies of water and food can be replenished. Thus, political or military control of an oa… (More on Oasis)