Three major features fill the Indian landscape: the Himalayas and associated ranges, a geologically young mountain belt, folded, faulted, and uplifted, that marks the nation's northern boundary and effectively seals India climatically from other Asian countries; the Peninsula, a huge stable massif of ancient crystalline rock, severely weathered and eroded; and the Ganges-Brahmaputra Lowland, a structural trough between the two rivers, now an alluvial plain carrying some of India's major rivers from the Peninsula and the Himalayas to the sea. These three features, plus a narrow coastal plain along the Arabian Sea and a wider one along the Bay of Bengal, effectively establish five major physical-economic zones in India.
Some of the world's highest peaks are found in the northern mountains: Kanchenjunga (8,598 m/28,208 ft), the third-highest mountain in the world, is on the border between Sikkim and Nepal; Nanda Devi (7,817 m/25,645 ft), Badrinath (7,138 m/23,420 ft), and Dunagiri (7,065 m/23,179 ft) are wholly in India; and Kamet (7,756 m/25,447 ft) is on the border between India and Tibet.
The Peninsula consists of an abrupt 2,400-km (1,500-mi) escarpment, the Western Ghats, facing the Arabian Sea; interior low, rolling hills seldom rising above 610 m (2,000 ft); an interior plateau, the Deccan, a vast lava bed; and peripheral hills on the north, east, and south, which rise to 2,440 m (8,000 ft) in the Nilgiris and Cardamoms of Kerala and Tamil Nadu. The Peninsula holds the bulk of India's mineral wealth, and many of its great rivers—the Narbada, Tapti, Mahanadi, Godavari, Krishna, and Kaveri—flow through it to the sea. The great trench between the Peninsula and the Himalayas is the largest alluvial plain on earth, covering 1,088,000 sq km (420,000 sq mi) and extending without noticeable interruption 3,200 km (2,000 mi) from the Indus Delta (in Pakistan) to the Ganges-Brahmaputra Delta (shared by India and Bangladesh), at an average width of about 320 km (200 mi). Along this plain flow the Ganges, Brahmaputra, Son, Jumna, Chambal, Gogra, and many other major rivers, which provide India with its richest agricultural land.