Indian Geography15 Concepts & Facts

Glaciers & Glacial Geomorphology Questions & Answers

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Glaciers are perennial bodies of recrystallized ice that move downslope under the pull of gravity and internal plastic deformation. Occupying alpine chains and polar latitudes, glaciers constitute Earth's largest reservoir of freshwater. The Himalayan orogen and adjoining Karakoram ranges, designated the Third Pole, contain the most extensive glacial ice outside the polar ice caps. The Siachen Glacier, spanning seventy-six kilometers in the East Karakoram Range, is the second-longest non-polar glacier globally. Other prominent Indian ice streams include the Gangotri Glacier in Uttarakhand, which feeds the Bhagirathi River, the Bara Shigri Glacier in Himachal Pradesh, and the Zemu Glacier beneath Kangchenjunga in Sikkim, which sustains the Teesta River.

Glacial geomorphic evolution proceeds through two primary mechanisms: plucking, where meltwater quarrying detaches rock blocks, and abrasion, where rock fragments gouge, striate, and polish bedrock. At high altitudes, these processes carve amphitheater-shaped hollows termed cirques (or corries), which frequently contain post-glacial tarn lakes. Headward recession of adjacent cirques sharpens ridges into knife-edge arêtes and steep pyramidal horns. Downvalley, glacial movement transforms steep V-shaped fluvial valleys into broad U-shaped glacial troughs with truncated spurs and tributary hanging valleys. Melting ice subsequently deposits unsorted glacial till, creating lateral moraines along valley flanks, medial moraines where parallel glaciers coalesce, and terminal moraines at the snout, alongside tear-drop drumlins, sinuous gravel eskers, and proglacial outwash plains.

Himalayan glaciers regulate the perennial runoff of major river basins—the Indus, Ganges, and Brahmaputra—which sustain north Indian agriculture. Cryospheric retreat under rising global temperatures has expanded proglacial moraine-dammed lakes, generating severe hazards of Glacial Lake Outburst Floods (GLOFs), as occurred during the 2013 Kedarnath event and the 2023 South Lhonak lake disaster in Sikkim. The National Disaster Management Authority prioritizes automated early warning systems and controlled siphoning to mitigate these hazards. For UPSC CSE and State PSC examinations, candidates must master the distinction between erosional and depositional glacial landforms, moraine classifications, Himalayan glaciological distribution, and disaster management protocols.

Key Concepts & Self-Assessment15 Key Facts

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A cirque (corrie or cwm) is an amphitheater-shaped erosional depression carved into bedrock at the head of a glacial valley.

A tarn is a small, steep-banked mountain lake that occupies the floor of a hollowed-out cirque after glacial ice melts.

An arête is a sharp, jagged narrow knife-edge rock ridge formed between two adjacent cirques or parallel U-shaped valleys.

Pyramidal horns (glacial horns), such as the Matterhorn in the Swiss Alps, form when three or more cirques erode a single mountain summit.

Glaciers transform steep V-shaped fluvial river valleys into wide, flat-bottomed U-shaped valleys known as glacial troughs.

Hanging valleys are tributary valleys whose floors stand elevated above the main glacial trough, producing plunging waterfalls.

Fiords (fjords) are deep, steep-walled, drowned glacial troughs formed along mountainous coasts that have been submerged by sea-level rise.

Roche moutonnée is an asymmetric bedrock knob featuring a smooth, polished up-glacier (stoss) side and a steep, plucked down-glacier (lee) slope.

Glacial till is unstratified, unsorted sediment deposited directly by melting ice, contrasting with sorted meltwater outwash deposits.

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Moraines are accumulation ridges of glacial till, classified by location into lateral, medial, ground, and terminal (end) moraines.

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Drumlins are elongated, streamlined, teardrop-shaped hills of compacted till aligned parallel to ice movement, often occurring in drumlin fields.

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Eskers are winding, sinuous ridges of stratified sand and gravel deposited by meltwater streams flowing within subglacial ice tunnels.

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Kames are steep-sided mounds of sand and gravel deposited along the margins of melting glaciers or in crevasses.

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Siachen Glacier, located in the Karakoram Range of Ladakh, spans approximately 76 kilometers, ranking among the world's longest non-polar glaciers.

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Gangotri Glacier in the Uttarkashi district of Uttarakhand terminates at Gaumukh, serving as the primary glacial source of the Bhagirathi River.

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Analytical perspective & practical exam advice from the Master10 academic board

Educator's Insight

Glaciers are slow-moving rivers of compacted ice that sculpt mountains through powerful mechanical weathering and deposition. As a glacier moves downslope, it plucks rock fragments and carves out bowl-shaped hollows called cirques. When cirque ice melts, it leaves behind a serene mountain lake known as a tarn. Glaciers also widen steep V-shaped river gorges into broad U-shaped valleys, leaving smaller tributary valleys stranded high above as hanging valleys that plunge into cascading waterfalls.

Glacial landforms are a favorite topic in UPSC prelims and SSC geography papers. A frequent question trap confuses erosional features with depositional ones. Remember this classification rule: cirques, arêtes, horns, and roche moutonnée are erosional, whereas moraines, drumlins, and eskers are depositional. Examiners often ask about drumlins, which resemble inverted spoons or an egg-basket topography aligned parallel to ice movement. Also revise India's key glaciers, noting Siachen in the Karakoram and Gangotri in Uttarakhand.

Glaciers & Glacial Geomorphology Questions & Answers

Key Concepts & Self-Assessment15 Key Facts

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