Plain

Plain, expanse of nearly level land, usually surrounded by higher land forms. About half of the world's land area is made up of plains, and they are found on ocean and sea floors as well. On land, there are three major kinds of plains: coastal, inland, and flood. Coastal plains stretch along seacoasts and often slope from sealevel to higher land. Inland plains are found in the interior of continents. Flood plains occur along rivers and are formed by materials (silt, sand, mud) deposited when the rivers overflow during floods. Depending on the climate, plains can be very fertile areas conducive to farming. A large percentage of the world's population lives on plains because they are food-producing, easy to build on, and to travel across.