The Himalayan Ranges — Part II

Important Valleys of the Himalayas

Himalayan valleys are formed by the interplay of tectonic activity, river erosion, and glacial action. They are of immense geographic, economic, and strategic significance.

Classification of Himalayan Valleys

• Strike Valley (Longitudinal Valley): Runs parallel to the mountain ridges; formed in synclines.
• Transverse Valley: Formed by rivers cutting across the mountain ranges (antecedent rivers).
• Dun/Doon Valleys: Structural valleys between Shiwaliks and Lesser Himalayas; flat-floored.

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Major Valleys

Kashmir Valley

• Located between the Greater Himalayas (north) and the Pir Panjal Range (south).
• Average elevation: 1,585 m above mean sea level.
• Shape: Synclinal basin; bowl-shaped, surrounded by ranges.
• Sediments: Alluvial, lacustrine (lake), fluvial, and glacial deposits.
• The Jhelum River meanders through the valley, draining through a gorge cut in the Pir Panjal.
• Vulnerability: Due to limited drainage outlets, Kashmir Valley is highly susceptible to flooding.

Karewas:

• Thick deposits of glacial clay, lacustrine deposits, and moraines found in Kashmir Valley and Bhadarwah Valley (Jammu Division).
• Appear as flat-topped mounds bordering the valley on all sides.
• Formed when the entire valley was submerged in water during the Pleistocene Period (~1 million years ago); drained when the Baramullah Gorge was created by endogenic forces.
• Karewa thickness: ~1,400 m.
• Economic significance: Cultivation of Zafran (Kashmir saffron) — a GI-tagged product; also almonds, walnuts, apples.

Zabarwan Range:

• Small range between Sind River Valley and Lidder River Valley in the north-central part of Kashmir Valley.
• Overlooks Dal Lake and the Mughal Gardens of Srinagar.
• Houses the Indira Gandhi Memorial Tulip Garden — largest tulip garden in Asia.
• Contains Dachigam National Park — home to the critically endangered Kashmir Stag (Hangul).

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Kangra Valley (Himachal Pradesh)

• A strike valley between the Dhauladhar Range (north) and Shivalik Hills (south).
• Extends from the foot of Dhauladhar to the Beas River.
• Famous for: Kangra Tea — registered Geographical Indication (GI) product; grown in Dharamshala, Palampur, and Baijnath.

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Kulu Valley (Himachal Pradesh)

• A transverse valley formed by the Beas River between Manali and Larji.
• Famous for: tourism, apple orchards, Kullu Dussehra festival.

Strike Valley vs Transverse Valley: A strike valley runs parallel to the ridges (along the strike direction of rock strata). A transverse valley cuts across rock strata — formed by antecedent rivers that predate the mountain uplift.

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Doon Valley (Uttarakhand)

• Lies between the Lesser Himalayas and the Shiwaliks.
• Contains Dehradun — capital of Uttarakhand.
• Formed by the downcutting of the Song River and Asan River.
• Other notable duns: Kotlidun, Patlidun, Chandigarh-Ambala area.

Other Notable Valleys

Note: Both Kathmandu and Pokhara valleys are highly vulnerable to earthquakes due to liquefaction potential of loosely deposited clayey alluvium.

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Snow and Glaciers

The Snowline

The snowline is the lowest level of perpetual snow on a mountain. Its elevation varies based on:

1. Latitude — higher latitude = lower snowline
2. Precipitation — more precipitation on south-facing slopes = lower snowline
3. Aspect — south-facing slopes receive more solar radiation = higher snowline

The western Himalayas receive less total precipitation (mainly from Western Disturbances as snowfall); the eastern Himalayas receive more precipitation from the SW Monsoon. This, not latitude alone, explains the difference in snowline elevation.

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Major Glaciers of the Himalayas

A glacier is a large body of crystalline ice, snow, rock, and sediment that moves slowly downslope under the influence of gravity. Formed by the perennial accumulation and compaction of snow over decades.

Total count: ISRO study identified 34,919 glaciers spread over 75,779 sq km in the Indus, Ganga, and Brahmaputra basins (including Trans-Himalayas and Karakoram).

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Glaciers of the Karakoram Range

The maximum development of glaciers outside the polar regions occurs in the Karakoram Range.

Siachen Glacier is a piedmont glacier — formed when valley glaciers spread out into a flat area. It originates at Indira Col West on the Indira Ridge.

Fedchenko Glacier (Pamirs, Tajikistan) = second largest glacier outside polar regions (~74 km); Hispar = third largest.

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Glaciers of Jammu & Kashmir

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Glaciers of Ladakh

Drang Drung Glacier:

• Near Pensi La Pass in Zanskar Himalayas.
• Source of Doda River — the largest tributary of the Zanskar River.

Shafat Glacier: Feeds the Suru River (tributary of Indus).

Pensilungpa: Northwest corner of Zanskar Valley; also feeds Suru.

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Glaciers of Himachal Pradesh

In HP, glaciers are locally called shigri. Old name of Chenab = Askini.

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Glaciers of Uttarakhand

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Glaciers of Sikkim

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The Purvanchal (Eastern Hills)

• A chain of hills in Northeast India, forming the eastern flank of the Himalayan arc.
• These are the continuation of the Himalayan system but geologically distinct.
• Orientation: Generally north-south in Nagaland, Manipur, Mizoram; curves eastward in Arunachal.

Major Hill Ranges

Shillong Plateau (Meghalaya Plateau): A part of the ancient Gondwana landmass — geologically it is a detached part of the Peninsular Plateau, not part of the Himalayas. Also called the "Meghalaya Plateau." The Garo-Rajmahal gap separates it from the main peninsula.

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Himalayan Rivers — Classification and Key Concepts

Antecedent Rivers

• Himalayan rivers (Indus, Ganga tributaries, Brahmaputra) are antecedent — they predate the Himalayas.
• They maintained their original courses as the mountains rose beneath them.
• This explains why they cut deep gorges through the ranges rather than being diverted.
• Evidence: Indus Gorge (near Nanga Parbat), Brahmaputra Gorge (near Namcha Barwa) — among the world's deepest gorges.

River Capture / Piracy

• Due to the asymmetrical structure of the Himalayas (steeper south slopes), the river systems on the south have greater erosive power.
• This has led to river capture (piracy) — southward-flowing rivers capturing the upper courses of rivers flowing northward.

Gorges vs. Valleys

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Glacial Lake Outburst Flood (GLOF) — Concept and India's Vulnerability

What is a GLOF?

A GLOF occurs when water retained by a glacial lake is suddenly released due to:

• Moraine dam failure (dam made of glacial debris)
• Displacement wave from landslide/ice avalanche into lake
• Permafrost degradation (thawing of frozen ground supporting moraines)
• Earthquake triggering

India's GLOF Vulnerability

• ISRO identified 676 glacial lakes in Indian Himalayan basins; 601 have expanded more than twice since the baseline period.
• States at risk: Uttarakhand, Himachal Pradesh, Sikkim, Arunachal Pradesh.
• Climate change is accelerating glacier melt → more and larger glacial lakes → greater GLOF risk.

Kedarnath Disaster (June 2013)

• Chorabari Glacier lake burst due to extreme rainfall.
• One of India's worst natural disasters in the Himalayas: ~5,700 people dead/missing.
• Triggered massive flash floods in Mandakini and Alaknanda river systems.

Sikkim GLOF (October 2023) — Detailed Analysis

• Lake: South Lhonak Lake, North Sikkim (~5,200 m elevation).
• Trigger: Permafrost landslide (~14.7 million m³) → 20 m displacement wave → moraine breach.
• Discharge: ~50 million m³ of water released; peak flow 48,500 m³/s.
• Trail: 385 km along Teesta River to Bangladesh.
• Deaths: ~92 confirmed, 74+ missing.
• Infrastructure: Teesta III Dam destroyed; 31 bridges lost; 25,900+ buildings damaged.
• Climate link: ICIMOD confirmed climate change accelerated South Lhonak Lake expansion.

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UPSC Corner

Key One-Liners for Prelims

• Bara Shigri = largest glacier in HP; feeds Chenab (via Chandra River)
• Gangotri Glacier = source of Bhagirathi = source of Ganga; in Uttarkashi
• Zemu Glacier = largest glacier in eastern Himalayas; near Kangchenjunga
• Siachen Glacier = largest outside polar regions = 75 km = world's highest battlefield
• Karewas = deposits of glacial + lacustrine material in Kashmir = ideal for saffron cultivation
• Kangra Tea = GI-tagged product from Kangra Valley, HP
• Dachigam National Park = Zabarwan Range = Kashmir Stag (Hangul) = Critically Endangered
• Shillong Plateau = geologically part of Peninsular (Gondwana) plateau, NOT Himalayas
• Antecedent rivers = Himalayan rivers; predate the mountains
• GLOF = Glacial Lake Outburst Flood; 601 of 676 Indian glacial lakes have expanded >2x (ISRO 2024)
• Kedarnath 2013 = Chorabari Glacier lake burst; 5,700+ deaths
• Sikkim GLOF 2023 = South Lhonak Lake; 92 deaths; Teesta III dam destroyed

Mains GS1 Questions

1. "What are glacial lake outburst floods (GLOFs)? Analyze India's vulnerability and suggest mitigation measures."
2. "Discuss the significance of the Purvanchal hills in the context of India's northeastern geography and security."
3. "What are karewas? Discuss their formation and economic significance."
4. "Explain the concept of antecedent drainage with examples from the Himalayas."
5. "How is climate change altering the cryosphere of the Himalayas? Discuss implications for water security."

MCQ Trap Awareness

• Trap: "Gangotri is the source of the Ganga" → Technically incorrect — Gangotri is the source of the Bhagirathi, which joins the Alaknanda at Devprayag to form the Ganga.
• Trap: "Zemu glacier is in Uttarakhand" → Incorrect — it is in Sikkim (near Kangchenjunga).
• Trap: "Siachen is entirely in India" → The glacier is under Indian administration but the sovereignty is disputed; it is in the Karakoram.
• Trap: "Shillong Plateau is part of the Himalayas" → Incorrect — it is geologically a detached piece of the Peninsular Plateau (Gondwana).
• Trap: "Beas river originates from Rohtang Pass" → More precisely it originates from Beas Kund, a glacial lake near Rohtang Pass.