oasis (ōāˈsĭs) [key], an area within a desert where the water table reaches the surface, with enough moisture to permit the growth of vegetation. The water may come up to the surface in springs, or it may collect in mountain hollows. In deserts such as the Sahara, artificial oases have been successfully created by using tube wells, which tap deep sources of groundwater. Oases vary in size, ranging from a pond with a group of date palms to the oasis cities of the deserts of Arabia with extended agricultural cultivation. The ice-free dry valleys of Antarctica are also called oases because they support life surrounded by a barren ice desert.