(a) Coastal plains : The plains situated near a sea coast are called coastal plains. They are formed by the sea waves after sea bottoms have emerged. The newly emerged plain is generally broad and wide and comprise of loosely compacted layers of mud and sand. Many coastal plains increased in which towards the sea because the sea waves continue adding matter to it.
(b) Karst plains : These plains are formed by the action of underground water, dissolving the regions made of chalk or limestone are called Karst plains. They are often flat-bottomed. Due to wind erosion and differential weathering, the topography is etched and rounded or even polished in a curious manner. Some of the relief features are quite fantastic in shape, especially the pebbles and other fragments that litter the surface of these plains.
(c) Peneplains : Very low undulating plains are called peneplains. They are almost plains.
(d) Cuestiform plains : The plains marked by a concentric arrangement of ridges and lowlands are called Cuestiform plains. Paris and London are the typical examples of such plains. They are made by river action on hard and soft rocks. Consequently they become rolling like the downs of S.E. England.
