Subdivisions of the continental surfaces distinguished from one another on the basis of the form, roughness, and surface composition of the land. These areas of distinctive landforms are the product of various combinations and sequences of events involving both deformation of the Earth's crust and surficial erosion and deposition by water, ice, gravity, and wind. The pattern of landform differences is strongly reflected in the arrangement of such other features of the natural environment as climate, soils, and vegetation. These regional associations must be carefully reckoned with by anyone planning activities as diverse as agriculture, transportation, city development, and military operations.