The HimalayasThe Himalayas

The Himalayas are divided longitudinally into four distinct parallel mountain ranges from north to south, each with unique geological and structural features.

• Trans-Himalayas (Tethys Himalayas): Located north of the Great Himalayas, containing the Karakoram, Zaskar, Ladakh, and Kailash ranges. Mount Godwin-Austen (K2, 8611m) lies in the Karakoram range.
• Greater Himalayas (Himadri): The northernmost and highest continuous range with an average elevation of 6,000 meters. Composed of central crystalline rocks (granites and gneisses) and houses peaks like Mt. Everest, Kanchenjunga, and Nanga Parbat.
• Lesser Himalayas (Himachal): Rugged range running parallel to the south of Himadri, averaging 3,700 to 4,500 meters. Features famous hill stations and valleys like Kashmir Valley, Kangra, and Kullu Valley.
• Outer Himalayas (Shiwaliks): The outermost southern foothills composed of unconsolidated sediments brought down by rivers. Altitude varies from 900 to 1,100 meters, featuring flat-structural valleys called Duns (Dehra Dun) in the west and Duars in the east.

Sir Sidney Burrard demarcated the Himalayas regionally on the basis of river valleys flowing across the mountain ranges from west to east.

• Punjab Himalayas (Kashmir Himalayas): Stretches between the Indus and Sutlej rivers (approx. 560 km). Also known regionally as Kashmir and Himachal Himalayas, featuring Karewa formations ideal for saffron cultivation.
• Kumaon Himalayas: Stretches between the Sutlej and Kali rivers (approx. 320 km). Contains major peaks like Nanda Devi, Kamet, Trishul, and source regions of the Ganga and Yamuna rivers.
• Nepal Himalayas: Stretches between the Kali and Tista rivers (approx. 800 km - the longest section). Houses the highest concentration of ultra-prominent peaks including Mount Everest, Makalu, Dhaulagiri, and Annapurna.
• Assam Himalayas: Stretches between the Tista and Dihang (Brahmaputra) rivers (approx. 720 km). Characterized by a sharp southward bend of the mountains near the eastern syntaxial bend (Namcha Barwa).

Mountain passes have served as historic trade routes and strategic military checkpoints across the Himalayan barrier, connecting India with Tibet, China, and Central Asia.

• Zoji La Pass (Jammu & Kashmir): Located on the Zaskar range, connecting Srinagar to Leh. It forms an important road link on the Srinagar-Leh highway (NH 1D).
• Shipki La Pass (Himachal Pradesh): Located in the Zaskar range, through which the Sutlej River enters India from Tibet. It serves as a border post for trade with China.
• Nathu La & Jelep La (Sikkim): Nathu La (part of ancient Silk Road) connects Sikkim with Tibet's Chumbi Valley and was reopened for border trade in 2006. Jelep La is another strategic pass nearby.
• Bomdi La & Diphu (Arunachal Pradesh): Bomdi La connects Arunachal Pradesh with Lhasa. Diphu pass is situated near the tripoint of India, China, and Myanmar border.

The Himalayan range takes sharp hairpin bends at its eastern and western extremities known as syntaxial bends, bounded by major tectonic boundary faults.

• Western Syntaxial Bend: Occurs near Nanga Parbat where the Indus River cuts a deep gorge through the mountains, turning sharply southwards.
• Eastern Syntaxial Bend: Occurs near Namcha Barwa where the Brahmaputra (Dihang) River enters India after taking a hairpin bend around the eastern extremity.
• Main Central Thrust (MCT): Tectonic fault separating the Greater Himalayas from the Lesser Himalayas.
• Main Boundary Fault (MBF) & HFT: MBF separates the Lesser Himalayas from the Shiwaliks, while the Himalayan Frontal Thrust (HFT) separates the Shiwaliks from the Indo-Gangetic Plains.