The Peninsula proper is an old, geologically stable region with an average elevation between 300 and 1,800 meters. The Vindhya Range constitutes the main dividing line between the geological regions of the Indo-Gangetic Plain and the Peninsula. This range lies north of the Narmada River, and when viewed from there, it is possible to discern the prominent escarpments that rise between 800 and 1,400 meters. The Vindhya Range defines the north-central and northwestern boundary of the Peninsula, and the Chota Nagpur Plateau of southern Bihar forms the northeastern boundary. The uplifting of the plateau of the central Peninsula and its eastward tilt formed the Western Ghats, a line of hills running from the Tapti River south to the tip of the Peninsula. The Eastern Ghats mark the eastern end of the plateau; they begin in the hills of the Mahanadi River basin and converge with the Western Ghats at the Peninsula's southern tip.
The interior of the Peninsula, south of the Narmada River, often termed the Deccan Plateau or simply the Deccan (from the Sanskrit daksina
, meaning south), is a series of plateaus topped by rolling hills and intersected by many rivers. The plateau averages roughly 300 to 750 meters in elevation. Its major rivers--the Godavari, the Krishna, and the Kaveri--rise in the Western Ghats and flow eastward into the Bay of Bengal.
The coastal plain borders the plateau. On the northwestern side, it is characterized by tidal marshes, drowned valleys, and estuaries; and in the south by lagoons, marshes, and beach ridges. Coastal plains on the eastern side are wider than those in the west; they are focused on large river deltas that serve as the centers of human settlement.
India's offshore islands, constituting roughly one-quarter of 1 percent of the nation's territory, lie in two groups located off the east and west coasts. The northernmost point of the union territory of the Andaman and Nicobar Islands lies 1,100 kilometers southeast of Calcutta. Situated in the Bay of Bengal in a chain stretching some 800 kilometers, the Andaman Islands comprise 204 islands and islets, and their topography is characterized by hills and narrow valleys. Although their location is tropical, the climate of the islands is tempered by sea breezes; rainfall is irregular. The Nicobar Islands, which are south of the Andaman Islands, comprise nineteen islands, some with flat, coral-covered surfaces and others with hills. The islands have a nearly equatorial climate, heavy rainfall, and high temperatures. The union territory of Lakshadweep (the name means 100,000 islands) in the Arabian Sea, comprises--from north to south--the Amindivi, Laccadive, Cannanore, and Minicoy islands. The islands, only ten of which are inhabited, are spread throughout an area of approximately 77,000 square kilometers. The islands are low-lying coral-based formations capable of limited cultivation.
Data as of September 1995