There are four great classes of land forms: plains, plateaus, hill country, and mountains. Plains—the broad, flat or rolling, usually treeless country —rank first in total area.
Vast portions of the world's plains are sparsely populated, largely because of insufficient rainfall or too cold a climate. However, favorable soil, drainage, and climate enable some large plain areas to support moderate to dense population.
Plains constitute the great agricultural lands of the world. An example is the great American corn belt, an area that extends from central Kansas to eastern Ohio. As much as 70 to 80 percent of this land area is plowed and planted in crops.
Plains are characterized by gentle slopes. The local relief, or the difference in elevation between the lowest points to the highest points within a limited area, is generally less than 500 feet.
