There are four most broadly understood landforms on Earth. These are the mountains, hills, the plateaus and the plains. The plains support most of the population on Earth. Landforms can further be understood on the basis of Hierarchical order such as the first order landforms are Oceans and continents. The second-order landforms include abyssal ridges, plateaus, mountains, etc. The third order landforms consist of local landscapes such as sand dunes, caves, valleys, volcanoes, lakes, gorges, etc. The basis of this hierarchy is placed on the way in which these terrains are formed geologically.