Himalayan Geography: Ranges, Passes & UPSC Notes

Himalayan Geography: Ranges, Passes & UPSC Notes

The Himalayas are the youngest and highest mountain system on Earth, stretching approximately 2,400 km from the Indus gorge in the west to the Brahmaputra gorge in the east. Formed by the collision of the Indian and Eurasian tectonic plates about 50 million years ago, they continue to rise at approximately 1 cm per year. For UPSC, Himalayan geography is a foundational topic — covering physical features, passes, glaciers, river origins, and the mountain’s influence on India’s climate, drainage, and biodiversity.

Formation of the Himalayas

The Himalayas formed through the convergent collision of the Indo-Australian Plate with the Eurasian Plate during the Cenozoic era. The Tethys Sea — an ancient ocean between the two plates — was compressed and uplifted as the Indian plate pushed northward.

Key Events in Formation

The presence of marine fossils (including ammonites) in Himalayan rocks — particularly in the Spiti Valley and Ladakh — confirms the oceanic origin of these sediments. The Tethys Himalaya preserves these ancient sea-floor deposits.

Longitudinal Divisions (North to South)

The Himalayas are divided into three parallel ranges running from northwest to southeast, each with distinct geological and physical characteristics.

1. Great Himalayas (Himadri)

The northernmost and highest range, with an average elevation of 6,000 metres. It contains all peaks above 8,000 metres and is composed primarily of granite and gneiss.

Key features:

• Average width: 25 km
• Contains 14 peaks above 8,000 m (including Mount Everest at 8,849 m)
• Permanent snow cover and glaciers above the snowline (~4,500 m)
• Major peaks: Everest, Kangchenjunga, Nanga Parbat, Nanda Devi, Kamet, Annapurna
• Source of major rivers — Ganga (Gangotri), Yamuna (Yamunotri)

2. Lesser Himalayas (Himachal)

Located south of the Great Himalayas, with elevations ranging from 3,500 to 4,500 metres. This range is composed of highly compressed and altered rocks.

Key features:

• Average width: 50-80 km
• Contains most hill stations: Shimla, Mussoorie, Nainital, Darjeeling, Manali
• Important ranges: Pir Panjal (longest in Lesser Himalayas), Dhaula Dhar, Mahabharat Range
• Valleys: Kashmir Valley (between Pir Panjal and Great Himalayas), Kangra Valley, Kullu Valley
• The Pir Panjal Range separates the Kashmir Valley from the Jammu plains

3. Outer Himalayas (Siwaliks/Shivaliks)

The southernmost and lowest range, with elevations between 600 and 1,500 metres. Composed of unconsolidated river deposits — sandstone, conglomerate, and clay.

Key features:

• Average width: 10-50 km
• Youngest Himalayan range (formed from debris eroded from rising Himalayas)
• Duns/Doons: Longitudinal valleys between Siwaliks and Lesser Himalayas (e.g., Dehra Dun, Patli Dun, Kotli Dun)
• Terai: Marshy, forested belt at the foot of the Siwaliks
• Prone to landslides due to loose sedimentary composition

Comparison of Himalayan Ranges

Regional Divisions (West to East)

The Himalayas are also divided regionally:

Western Himalayas

Central Himalayas (Nepal Himalayas)

Contains the highest peaks — Everest (8,849 m), Kangchenjunga (8,586 m), Lhotse, Makalu, Dhaulagiri, and Annapurna. This section includes Nepal and the Indo-Nepal border region.

Eastern Himalayas

The Purvanchal hills — running north-south — are considered an extension of the Himalayan system. They include the Patkai Bum, Naga Hills, Manipur Hills, Mizo Hills (Lushai Hills), and Tripura Hills.

Important Himalayan Passes

Passes are critical for trade, military movement, and cultural exchange. They appear frequently in UPSC Prelims.

Key Passes

UPSC Mnemonic for Passes (West to East)

Karakoram → Zoji La → Rohtang → Shipki La → Bara Lacha La → Mana → Niti → Nathu La → Jelep La → Bomdi La

Glaciers of the Himalayas

Himalayan glaciers are the largest ice mass outside the polar regions — often called the Third Pole. They feed India’s perennial rivers and are critical to water security for over a billion people.

Major Glaciers

Glacier Retreat and Climate Change

Himalayan glaciers are retreating at an alarming rate. The ISCCC (Indian Space Research Organisation) estimated that over 85% of Himalayan glaciers showed retreat between 2000 and 2020. This has implications for:

• Reduced dry-season river flow in the long term
• Increased glacial lake outburst floods (GLOFs) in the short term
• Threat to hydropower infrastructure
• Impact on agriculture dependent on glacial meltwater

Trans-Himalayan Ranges

Located north of the Great Himalayas, the Trans-Himalayan ranges include:

The Trans-Himalayas are drier, colder, and more barren than the main Himalayan ranges because they lie in the rain shadow.

Himalayas and Indian Climate

The Himalayas profoundly influence India’s climate:

1. Monsoon Barrier — force moisture-laden southwest monsoon winds to rise, causing orographic rainfall on the Indian side
2. Cold Wave Shield — block bitter cold winds from Central Asia, keeping the Indo-Gangetic Plain warmer than equivalent latitudes elsewhere
3. Biodiversity Gradient — altitudinal zones support tropical to alpine vegetation within short horizontal distances
4. River Systems — snowmelt and glacial melt feed India’s perennial river systems

Peninsular Plateau of India: Features & Resources River Systems of India: Himalayan & Peninsular

Frequently Asked Questions