Overview of North Indian geography
The geographical boundaries of North India correspond to a historical and cultural reality, rather than to a unifying relief or topography. The territory encompasses the Himalayas and their foothills to the north and east, part of the Deccan plateau in the center, the Indo-Gangetic plain to the west, north and northeast, and the Gujarat peninsula to the west. North India includes the mountain states of Jammu and Kashmir, Uttarakhand, Himachal Pradesh, Uttarakhand, Sikkim, Arunachal Pradesh and the territory of Ladakh; the plains states of Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, Uttar Pradesh, Bihar, Jharkhand, Chhattisgarh, Odisha, West Bengal and Assam, and the territories of Delhi and Chandigarh. Finally, there are the northeastern tribal states of Meghalaya, Nagaland, Maripur, Tripura and Mizoram, with their rugged topography and tropical climate. More commonly, northern India can be divided into two major geographical zones: the Himalayas and the river plains of the Ganges and Brahmaputra.
The Himalayas
80 million years ago, India was an island 6,400 kilometers off the coast of Asia. The northward-moving Indian Plate collided with the Eurasian Plate around 62 million years ago. This dating was obtained in 2020 using a multi-disciplinary approach combining stratigraphic, sedimentological and geochronological studies. The Indian plate continues to advance at a rate of around 5 centimetres per year, sinking beneath the Eurasian plate and triggering regular high-magnitude earthquakes. The sea that separated India from Asia disappeared with the collision. But there are signs of it. The summit of Mount Everest, in Nepal, is made of marine limestone.
The Himalayas form a 2,400-kilometer-long impenetrable natural barrier in the shape of an arc. It separates the Indian subcontinent from East Asia. The range begins in the Karakoram, a region bordering Pakistan, India and China. It ends in Assam, in northeast India, where the Brahmaputra River flows. Some geologists link the Himalayan range to its western and eastern foothills, in Baluchistan and Burma. Beyond this expert debate, the Himalayas are actually a geological formation of three parallel chains that form a mountainous block 250 km to 400 km wide. The sub-Himalayan range, also known as the Shivalik Hills, is the lowest. It rises above the Indian Indo-Gangetic plateau in the north and northeast of the country. Its average elevation is 1,200 metres. The second range, known as the "Lower Himalayas", rises between 2,000 and 5,000 meters. It is mainly located in India, and forms the main relief of the states and territories of Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand, northern West Bengal, Sikkim and Arunachal Pradesh. The third range, or "High Himalaya", is the oldest geologically speaking, and the highest. It is home to 10 of the 14 peaks over 8,000 metres high. Of these, only one is in India: Kanchenjunga (8,586 m), straddling southern Nepal and Sikkim. India does, however, boast 7 peaks over 7,000 metres, most of them in northern Uttarakhand.
The geological formation of these three mountain ranges differs from one another, so it's easy to see that they are the result of events that occurred at different times. The oldest chain is the "High Himalayas", composed essentially of fossilized marine sediments. The Tethys Sea disappeared when it met the Eurasian Plate. The Lower Himalayan range is made up mainly of crystalline rocks, but also of sedimentary series. The sub-Himalayan range has a geology formed in the Tertiary era. Despite the Himalayas' proximity to the tropics, areas above 5,000 metres are snow-covered all year round. The meaning of the word " Himalaya " comes from the Sanskrit word for "abode of snow". The Himalayas are home to numerous glaciers, which flow into the lower valleys to form rivers.
River plains
The Ganges and Brahmaputra rivers, among the longest in the world, flow directly from Himalayan glaciers. The Ganges rises at the foot of the Gangotri glacier in Uttarakhand. The Brahmaputra crosses Tibet from west to east, before reaching Assam, forming the world's deepest valley. It continues its course through Bangladesh. The two rivers meet north of the Bay of Bengal, where they flow into the world's largest delta, the Sundarbans. Together with the Indus Valley in Pakistan, these three rivers form the Indo-Gangetic Plateau, which abuts the Himalayan chain. The low elevation of the terrain, 350 metres above sea level, creates the illusion of geographical uniformity. In reality, the Indo-Gangetic plain comprises a number of different zones. At the foot of the Shivalik hills is a thin strip of rock and pebbles unsuitable for agriculture. Just below, the Tarai zone forms a belt of tall grass and sal forests, with clay soil. On the Brahmaputra side, the approach to the valley, known as the Douars, consists of alluvial floodplains. The Ganges plateau is criss-crossed by numerous tributaries that form silty tongues of land. This area is considered the granary of India. It stretches from Punjab to Haryana, then forms a wide band around the Ganges valley and the Brahmaputra river. The Indo-Gangetic plateau is the world's largest alluvial zone. Flat, fed by underground springs and sparsely forested, it is the world's largest agricultural area and home to over 400 million people.
