India has diverse physical features ranging from the Himalayan mountains in the north to the coastal plains and islands in the south. The country can be divided into six major physiographic divisions - the Himalayan mountains, northern plains, peninsular plateau, Indian desert, coastal plains and islands. The northern plains are formed by the interplay of the Indus, Ganges and Brahmaputra river systems. The peninsular plateau consists of the older crystalline and metamorphic rocks of the Deccan trap and forms the tableland south of the Narmada River. India also has coastal plains along the western and eastern coasts and island groups of Lakshadweep and Andaman & Nicobar islands.