Mountain: high land mass projecting conspicuously above its surroundings and usually of limited width at its summit. Valleys: a long depression in the land surface, usually containing a river, formed by erosion or by movements in the earth's crust. Plateau: elevated, level or nearly level portion of the earth's surface, larger in summit area than a mountain andbounded on at least one side by steep slopes, occurring on land or in oceans. Plains: a broad level expanse, as a part of the sea floor or a lunar mare. Glacier: a slowly moving mass of ice originating from an accumulation of snow. It can either spread outfrom a central massor descend from a high valley. Stream: A flow of water in a channel or bed, as a brook, rivulet, or small river Delta: a usually triangular alluvial deposit at the mouth of a river. Estuary: t he part of the wide lower course of a river where its current is met by the tides. Gulfs: a large ...