India occupies the greater part of a peninsular subcontinent fronting on two great arms of the Indian Ocean—the Arabian Sea on the west and the Bay of Bengal on the east. Just off its southern coast lies the island nation of Sri Lanka, separated from the mainland by the Palk Strait. Land boundaries are shared with Pakistan, China. Nepal, Bhutan, Burma, and Bangladesh. On the northwestern frontier is the disputed territory of Kashmir; although India claims all of Kashmir, it holds only the southern part, the rest being occupied by Pakistan.
India has three distinct physical regions: the Himalayas, the Ganges Plain, and the Deccan Plateau.
The Himalayas extend along the nation's northern border, forming a high mountain wall, 100 to 150 miles (160 to 240 km) wide, that separates the Indian subcontinent from Asia's interior. The region consists of a complex system of mountain ranges that divide into three roughly parallel chains: the Siwalik Hills, Lesser Himalayas, and Great Himalayas. Several other ranges strike off from the Himalayas along the Burmese border.
In the towering, snow-covered ranges of the Great Himalayas are many of the world's highest peaks. Though the highest summits are in Nepal and China, numerous peaks in India exceed 20,000 feet (6,100 m) above sea level. Kanchenjunga, the nation's highest, reaches 28,209 feet (8,598 m). Heights of 5,000 to 15,000 feet (1,500 to 4,500 m) mark the Middle Himalayas, which, in turn, give way to low foothills of less than 4,000 feet (1,200 m) in the Outer Himalayas.
Huge glaciers and snowfields on the flanks of the higher ranges feed rivers that flow southward through deep gorges and narrow, steep-sided valleys to the Ganges Plain.
The Ganges Plain is a broad, alluvial lowland, 100 to 300 miles (160 to 480 km) wide, spanning the country south of the Himalayas. It consists mainly of the fertile basin of the Ganges River. The land is generally flat, with a slight downward slope toward the east. Much of India's farmland and many of its largest cities are on the plain, one of the most densely settled areas on earth. Only the Thar (Great Indian) Desert, an almost barren area in the west, is sparsely populated and little used.
The Deccan Plateau, often called simply the Deccan, occupies the peninsula south of the Ganges Plain. It is roughly triangular in shape and consists of a vast tableland broken by river valleys, with areas of rolling hills. The land slopes gently downward toward the east.
Fringing the Deccan on the north are the Chota Nagpur Plateau and a maze of low mountains, including the Vindhya and Satpura ranges, in the west. Elsewhere the plateau is bordered by escarpments, known as ghats. The Western Ghats, 3,000 to 5,000 feet (900 to 1,500 m) high, form a sheer wall that drops abruptly to a narrow coastal plain along the Arabian Sea. The Eastern Ghats, in contrast, consist of low, disconnected ranges that slope gently toward a broader coastal plain along the Bay of Bengal. At the southern end of the peninsula, connecting the Eastern and Western Ghats, are the Nilgiri, Anaimalai, and Cardamom hills.
India's principal river is the Ganges. It flows from the western Himalayas to the Bay of Bengal—a distance of more than 1,500 miles (2,400 km). Together with such tributaries as the Yamuna, Son, Ghaghara, and Gandak, the Ganges drains most of the mountains and the plains and part of the Deccan. In the northeast the Brahmaputra River follows a tortuous course through the Assam Valley from China and merges with the Ganges to form a vast delta, lying partly in India and partly in Bangladesh. The Ravi and Sutlej rivers, part of the Indus system, flow across northern India to Pakistan.
The Deccan is drained primarily by the eastward-flowing Mahanadi, Godavari, Krishna, and Cauvery rivers. They form large, fertile deltas at their mouths on the Bay of Bengal. The Narmada and Tapti are the only sizable rivers flowing to the Arabian Sea.
India's rivers are used extensively for irrigation; they are also used for hydroelectric power and navigation. Of particular importance is the Indus River system, which provides water for the dry Punjab region of India and Pakistan. The Indus Waters Treaty of 1960 allocates the waters of the Ravi and Sutlej to India and the waters of the Indus and its other major tributaries to Pakistan. Bhakra Dam, on the Sutlej River, is the largest of many dams in India and one of the highest dams in the world.
Sheltered by the Himalayas from the climatic extremes of Asia's interior, most of India has a tropical or subtropical climate, strongly influenced by the monsoonal wind system of southern Asia. In India the monsoons are characterized by an outward flow of relatively cool, dry air from central Asia during winter and a reverse flow of warm, moist air from the sea in summer. Other factors—such as latitude, elevation, nearness to the oceans, and location on the windward or leeward side of mountains—help determine the climate of any given area. In the Himalayas, for example, climate varies from humid subtropical in the eastern foothills to perpetually cold in the highest ranges.
Three seasons are generally recognized in India—the cool, the hot, and the rainy.
The cool season lasts from October or November until early March. Average temperatures in December and January, the coolest months, vary from about 55° F. (13° C.) on the northern edge of the Ganges Plain to between 70° and 80° F. (21° and 27° C.) in the coastal cities of the south. For most of the country this is the dry season. A notable exception is the southeastern coast, which receives much of its annual rainfall with the winter, or northeast, monsoon in October, November, and December. There is heavy snowfall in the Himalayas.
The hot season prevails from about mid-March until June; it is extremely dry. Temperatures rise rapidly over most of the country, reaching averages of 85° to 95° F. (29° to 35° C.) in May, the hottest month. Daytime highs often exceed 100° F. (38° C.), especially on the Ganges Plain. Nights bring only slight relief from the intense heat.
The rainy season begins in June with the onset of the summer, or southwest, monsoon and continues through September. Most of India receives more than 80 per cent of its annual rainfall during this period. In addition to rain, the summer monsoon brings a reduction in the heat, but causes high, often oppressive, humidity. The heaviest rains, totaling more than 100 inches (2,540 mm) a year, occur in the northeast and along the Malabar Coast in the southwest. At Cherrapunji, in Meghalaya state in the northeast, the annual average is about 425 inches (10,800 mm)—one of the highest in the world. Elsewhere rainfall usually varies from 20 to 80 inches (500 to 2,000 mm) a year. Only the Thar Desert receives less than 10 inches (250 mm).
The summer monsoon is vital to India's agriculture. The timing and the amount of the rains can mean the difference between a successful harvest and widespread crop failure and famine.
Long ago, most of India was forested. Except in the more remote mountains and hills, the trees were cut for firewood or timber, or to make room for agriculture. Today, forests cover only about a fifth of the land, with much of the rest being farmland. Scrub, dry grasses, and desert plants are the principal vegetation on most of the remaining land.
Forests grow mainly on the slopes of the Himalayas and Western Ghats and along the northern edge of the Deccan. Differences in climate and elevation produce many kinds of forest. The most widespread is the deciduous monsoon type, which grows in areas receiving 40 to 80 inches (1,000 to 2,000 mm) of rainfall a year. It contains such valuable timber trees as sal, teak, ebony, and rosewood. Dense tropical evergreen forests occur in parts of the southwest. In the Himalayas temperate forests of pine, spruce, fir, oak, poplar, and birch predominate. Bamboo, which grows throughout much of India, is widely used for making furniture, household items, and paper.
India has rich and varied wildlife, though most of the larger animals have been greatly reduced in number and range. Tigers, elephants, and rhinoceroses, once widespread, are now restricted mainly to remote mountain and forest regions. Lions have become extremely rare; they are found only in the Gir Forest of Gujarat. Large animals less affected by the encroachment of man include bears, wolves, leopards, cheetahs, hyenas, and deer. Monkeys and mongooses are among the most numerous of India's many small mammals. In some regions, the monkeys, seldom killed because they have religious significance to Hindus, have become serious pests, destroying valuable food crops. Snakes, crocodiles, and other reptiles abound in India. The poisonous cobra and krait, two of the world's deadliest snakes, cause thousands of deaths each year.