In the hierarchy of relief features, plains are Second-order landforms. This classification places them alongside mountains and plateaus as major structural units of the Earth’s crust. They are often formed by the deposition of sediment over millions of years or by the slow uplift of a shallow seabed. Unlike “Third-order” landforms, which are small features carved out by wind or water (like a single hill or a gully), plains represent massive, regional geographical units. Their status as a second-order feature highlights their importance in defining the fundamental topographic profile of the continents.