Physical Features of India

India has almost every kind of landscape the Earth can offer: snow-capped mountains, vast flat plains, an ancient rocky plateau, a sandy desert, long sea coasts and scattered islands. Geographers group all of this into six physical divisions. Learning these divisions is the backbone of Indian physical geography. The contrast between the young northern mountains and the old southern plateau is a constant source of examination questions.

The relief of India is divided into:

1. The Himalayan Mountains
2. The Northern Plains
3. The Peninsular Plateau
4. The Indian Desert
5. The Coastal Plains
6. The Islands

The Himalayas are young fold mountains that rise along the northern border. They are among the highest and youngest mountain ranges in the world, still slowly rising. They run in three roughly parallel ranges from west to east.

• The Himadri, or Great Himalayas, is the northernmost and highest range, with an average height above 6,000 metres and the loftiest peaks, including Mount Everest and Kanchenjunga. It is permanently snow-covered.
• The Himachal, or Lesser Himalayas, lies to the south. It contains famous hill stations and valleys such as Kashmir, Kangra and Kullu.
• The Shiwaliks, the outermost range, is the lowest. Between the Shiwaliks and the Lesser Himalayas lie flat valleys called Duns, such as the Dehra Dun.

The Himalayas are vital for three reasons. They block the cold winds from Central Asia. They force the monsoon to give rain. And they feed the great northern rivers.

The landscape itself shows that these mountains are young. Rivers such as the Indus, the Sutlej and the Brahmaputra are antecedent rivers: they are older than the mountains and kept cutting downward as the land rose, carving deep gorges and taking sharp U-turn courses around the range. The slopes are steep and prone to landslides. Together with the parallel fold ranges and frequent earthquakes, these features are the classic evidence of young fold mountains.

North of the Himalayas proper lie the trans-Himalayan ranges, chiefly the Karakoram, the Ladakh and the Zaskar ranges. The Karakoram holds some of the largest glaciers outside the polar regions. The most famous is the Siachen Glacier, which lies to the north of the Nubra Valley in Ladakh.

Mountain passes are the gateways through the wall.

• Nathu La: a pass in Sikkim on the India–China border, reopened in 2006 for border trade between the two countries.
• Shipki La: a pass in Himachal Pradesh through which the Sutlej river enters India.

Several Himalayan valleys are tested by their home state.

• Markha Valley: in Ladakh.
• Sangla Valley: in Himachal Pradesh, along the Baspa river.
• Yumthang Valley: in Sikkim, known for its flowers.
• Dzukou Valley: in Nagaland, among the eastern hills.

South of the mountains lie the Northern Plains. They were built over thousands of years by the deposits of three river systems (the Indus, the Ganga and the Brahmaputra) and their tributaries. The fine soil these rivers bring down is called alluvium. It makes these plains among the most fertile and densely populated lands in the world.

The plains are not uniform. The pebble-strewn belt along the foothills is the Bhabar. South of it lies the wet, marshy Terai. The older alluvium is called Bhangar, and the newer, more fertile alluvium laid down by floods each year is the Khadar.

The Peninsular Plateau is the oldest part of India, made of hard, ancient igneous and metamorphic rocks. It is a stable landmass that has changed little for a very long time. It has two broad parts.

• The Central Highlands lie to the north of the Narmada river. The Aravalli Hills, one of the oldest ranges in the world, lie on its western edge.
• The Deccan Plateau lies to the south. It is a triangular tableland bordered by the Western Ghats and the Eastern Ghats. The Western Ghats are higher and continuous. The Eastern Ghats are lower and broken. The two ranges meet in the Nilgiri Hills. A large part of the Deccan is covered with black soil formed from old lava flows.

The Deccan is a genuinely elevated surface. Bengaluru, for example, sits on the plateau at roughly 900 metres, far above lowland cities such as Delhi, Jodhpur or Nagpur. A small detached fragment of the same ancient block, the Mikir Hills, lies far away in north-east India.

• Aravalli Hills: the western edge of the highlands, about 670 million years old. Their highest peak is Guru Shikhar (about 1,722 metres), near Mount Abu in Rajasthan. The pilgrimage town of Pushkar lies beside these hills.
• Vindhya Range: runs north of the Narmada river. The Kaimur Hills are its eastern continuation. The riverside pilgrimage site of Omkareshwar, on an island in the Narmada, lies in the Vindhya region.
• Satpura Range: runs south of the Narmada, between the Narmada and the Tapi. The Mahadeo Hills of Central India belong to this range and lie along its northern edge. Moving south, one crosses the Mahadeo Hills, then the main Satpura belt, and then reaches the Sahyadri.
• Amarkantak: the plateau where the Vindhya and the Satpura systems meet through the Maikal Hills. The Narmada rises here.

The Narmada and the Tapi behave unlike most peninsular rivers. They flow westward through old rift valleys, troughs formed where blocks of the crust sank between faults. The Tapi flows to the south of the Satpura Range. One more range completes the picture: the Ajanta Range lies entirely within Maharashtra, whereas the Aravalli, Satpura and Sahyadri each spread across several states.

The Western Ghats are also known as the Sahyadri. They rise higher in the south than in the north. Their highest peak is Anai Mudi (2,695 metres) in Kerala. The Cardamom Hills of Kerala form their southern section, and the Anaimalai Hills lie nearby, just south of the Nilgiris. Because the Ghats are a global biodiversity hotspot, two expert panels, the Gadgil Committee and the Kasturirangan Committee, both reported on the ecological protection of the Western Ghats and recommended ecologically sensitive zones along the range.

The broken Eastern Ghats include several named groups.

• Nallamala Hills: in Andhra Pradesh. The temple town of Srisailam lies in these hills.
• Javadi Hills: in northern Tamil Nadu.
• Shevaroy Hills: in the Salem district of Tamil Nadu.
• Biligirirangan Hills and Seshachalam Hills: both also belong to the Eastern Ghats.

For map questions, fix the north-to-south order of the southern hills: Nallamala, then Javadi, then Nilgiri, then Anaimalai.

The plateau is rich in minerals, which is why most of India's mining regions are found here.

To the west of the Aravalli Hills lies the Indian Desert, also called the Thar Desert. It is a sandy, wavy plain of dunes that receives very low and unreliable rainfall, generally below 150 millimetres a year. Most of its streams are seasonal, and the Luni is the only large river of the region.

Along the edges of the Peninsular Plateau run narrow Coastal Plains.

• The Western Coastal Plain is a narrow strip between the Western Ghats and the Arabian Sea. It includes the Konkan, the Kannad and the Malabar coasts.
• The Eastern Coastal Plain is wider and lies between the Eastern Ghats and the Bay of Bengal. The large deltas of the Mahanadi, Godavari, Krishna and Kaveri rivers are found here. Chilika Lake, the largest saltwater lake in India, lies along this coast.

The eastern coast also holds a tidal curiosity. At Chandipur in Odisha, the sea recedes several kilometres twice a day at low tide, exposing the bare sea floor, and then returns.

India also has two groups of islands.

• The Lakshadweep Islands in the Arabian Sea are small coral islands built by tiny sea organisms.
• The Andaman and Nicobar Islands in the Bay of Bengal are larger and more numerous. India's only active volcano, on Barren Island, lies in this group. India's southernmost point, Indira Point, is also here. The highest point of the whole group is Saddle Peak (732 metres) in North Andaman.

Behind these surface features lies a story of very different ages. That story explains why the divisions look so different. India is built of three great structural units.

The Peninsular block is the oldest. It is a rigid, stable mass of ancient hard rock. It is a surviving fragment of the old super-continent of Gondwana. It has been stable for so long that it rarely suffers major earthquakes.

The Himalayas are the youngest. The Peninsular block drifted north and collided with the Asian landmass. That collision squeezed and folded the sediments of an ancient sea called the Tethys upward into mountains. This is why the Himalayas are young fold mountains. They are still rising and still earthquake-prone.

The Indo-Ganga–Brahmaputra Plain lies in between. It began as a great trough, or foredeep, formed in front of the rising Himalayas. Over millions of years, the rivers filled it with silt, forming the deep alluvium of the plains.

Relative words like oldest and youngest can be pinned to geological eras.

• Aravalli Hills: Pre-Cambrian, about 670 million years old, among the oldest fold mountains on Earth.
• Deccan Traps: the great lava flows of the Deccan poured out between the Cretaceous and the Eocene. Their weathering gave the black soil.
• Western Ghats: the present escarpment was uplifted in the Late Cenozoic, so it is younger than the rocks it stands on.
• Narmada–Tapi alluvium: the river deposits filling these rift valleys date from the Pleistocene.

The Himalayas are not the same along their whole length. From west to east they are divided into regional sections, each named after the rivers or area it lies in. These are: the Punjab (Kashmir) Himalayas, the Kumaon Himalayas, the Nepal Himalayas (which hold the highest peaks, including Everest), and the Assam Himalayas.

Each section has a signature peak. The Kumaon Himalayas hold Nanda Devi, the highest peak that lies entirely within India. The Assam (Arunachal) Himalayas end at Namcha Barwa, the great peak around which the Brahmaputra bends. A common trap pairs these with Nokrek: Nokrek is the highest point of the Garo Hills in Meghalaya, an outlier of the old plateau, and is not Himalayan at all.

Beyond the eastern end, the ranges take a sharp bend to the south. They run down the eastern border as a set of hills known together as the Purvanchal (including the Patkai, Naga, Manipur and Mizo hills). These are lower, forested ranges that separate India from Myanmar.