In
geography, a
plain is a flat area. Plains occur as
lowlands and at the bottoms of
valleys but also on
plateaus or
uplands at high
elevations. In a valley, a plain is enclosed on two sides but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains or cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometime termed a gap). Plains may have been formed from flowing
lava, deposited by water, ice, wind, or formed by
erosion by these agents from hills and mountains.