Glacial Landforms
Geography › Rocks, Erosion and Landforms · Topic 5.8
Glaciers are large masses of ice that move slowly under their own weight, and they shape the land by erosion and deposition. Erosional landforms include cirques, arêtes, horns, U-shaped valleys, hanging valleys and fjords, and depositional landforms include moraines, drumlins, eskers, kames and erratics. Glaciers cover about a tenth of the land, and Himalayan glaciers feed major Indian rivers.
6 min read · UPSC Prelims · Geography · Rocks, Erosion and Landforms
At a Glance
- Types Valley, ice sheet, piedmont, tidewater
- Erosional Cirque, arête, horn, U-valley, hanging valley
- Depositional Moraine, drumlin, esker, kame, erratic
- Indian glaciers Siachen, Gangotri, Zemu, Pindari
- Hazard Glacial lake outburst floods
- Exam link UPSC Prelims, Geography: Rocks, Erosion and Landforms
Where Does It Fit?
This is the eighth topic of the category on rocks, erosion and landforms. The previous topic described coasts, and this one covers the landforms of ice. The next and final topic of the category describes the landforms of deserts shaped by wind. Previous topic: Marine Landforms and Coastlines. Next topic: Aeolian Landforms of Deserts.
What Is a Glacier and How Does It Move?
In short: a glacier is a river of ice that slowly carves valleys and drops debris.
A glacier is a large mass of ice that forms on land where more snow falls in winter than melts in summer, so that the snow compacts into ice over many years. Once the ice is thick enough, it flows slowly downhill under its own weight and gravity, at a speed from a few centimetres to several metres a day. Glaciers occupy about 10 per cent of the Earth’s land area, mostly in Antarctica and Greenland. The main types are valley or alpine glaciers, confined to mountain valleys; ice sheets or continental glaciers, which cover vast areas such as Antarctica and Greenland; piedmont glaciers, which spread out at a mountain foot; and tidewater glaciers, which end in the sea. The features that moving ice leaves behind are called glacial landforms. The ice carries rock debris and so acts like a huge bulldozer and sandpaper, eroding the land in a way that rivers cannot.
What Are the Erosional Landforms of Glaciers?
| Landform | Description |
|---|---|
| Cirque (corrie, cwm) | An armchair-shaped hollow at the head of a glacier, cut by ice and frost action; may hold a small lake called a tarn |
| Arête | A sharp, knife-edged ridge between two cirques or valleys |
| Horn (pyramidal peak) | A pointed peak left when several cirques cut back into a mountain; the Matterhorn in the Alps is the classic example |
| U-shaped valley (glacial trough) | A valley widened and deepened by a glacier, with steep sides and a flat floor |
| Hanging valley | A tributary valley left high above the main trough; often ends in a waterfall |
| Truncated spur | A river valley spur that is cut off by the passage of a glacier |
| Fjord | A U-shaped valley drowned by the sea; Norway, Chile, New Zealand |
| Roche moutonnée and striations | Smoothed and polished rock outcrops and scratch marks showing the direction of ice flow |
What Are the Depositional Landforms of Glaciers?
- Moraines: ridges of debris carried or dropped by glaciers; terminal moraine at the end of the glacier, lateral moraine along the sides, medial moraine in the centre where two glaciers join, and ground moraine, a sheet of till left behind.
- Erratics: boulders carried far from their source and left in an area of different rock.
- Drumlins: oval, streamlined hills of till, elongated in the direction of ice movement, often in swarms, like an inverted boat.
- Eskers: long, winding ridges of sand and gravel deposited by streams flowing in tunnels under the ice.
- Kames and kettles: mounds of sand and gravel, and depressions left by melting blocks of buried ice, that often become kettle lakes.
- Outwash plain: a broad plain of sorted sand and gravel spread by meltwater streams beyond the ice front.
The material left by glaciers, unsorted, is called till, while meltwater deposits are sorted and layered. The distinction is helpful in Prelims questions.
What Are the Glaciers of India and Their Hazards?
The Himalayas, Karakoram and Hindu Kush, sometimes called the Third Pole, hold the largest ice volume outside the polar regions. The Siachen Glacier in the Karakoram, about 70 km long, is one of the longest glaciers outside the polar regions. The Gangotri glacier, about 30 km long, in Uttarakhand, is the source of the Bhagirathi, a headstream of the Ganga, and other glaciers are Zemu in Sikkim, Pindari and Milam in Uttarakhand, and many in Ladakh and Kashmir. Himalayan glaciers feed the Indus, Ganga and Brahmaputra systems, as in Himalayan Valleys, Snowline and Glaciers, so their melting affects water supply for millions.
Most Himalayan glaciers are retreating because of warming, and meltwater forms lakes behind moraines, which can burst in glacial lake outburst floods, GLOFs. In October 2023 a GLOF from South Lhonak lake in Sikkim damaged the Teesta valley and the Teesta III dam, and in 2013 and 2021 high-mountain disasters affected Uttarakhand. As an analytical point, the retreat of glaciers is a double risk: more water in the short term and floods, but reduced dry-season flow in the long term, so monitoring of glacial lakes and early warning in the valleys below are priorities for disaster management.
How Did Past Ice Ages Shape Landscapes?
During the Pleistocene epoch, which began about 2.6 million years ago, ice sheets repeatedly covered northern North America, northern Europe and parts of Asia. They carved the Great Lakes basins, scoured the Canadian Shield and left the fjords of Norway, and drumlins and moraines across northern Europe and North America. Sea level fell by over 100 metres during glaciation and rose after melting. The present interglacial epoch, the Holocene, began about 11,700 years ago.
Why Is This Topic Important?
- Landforms Terms frequently asked
- India Himalayan glaciers and rivers
- Climate Glacier retreat and GLOFs
What Came Next?
The next topic describes aeolian landforms of deserts. Next topic: Aeolian Landforms of Deserts.
Key People and Terms
- Cirque Armchair hollow at a glacier head
- Arete Sharp ridge between cirques
- Moraine Ridge of glacial debris
- Drumlin Streamlined hill of till
- Esker Winding ridge of sand and gravel
- GLOF Glacial lake outburst flood
Exam Corner
Points to Remember
- Glaciers cover about 10 per cent of land.
- U-shaped valleys are glacial; V-shaped are fluvial.
- Matterhorn is a horn.
- Siachen is about 70 km long.
- Gangotri feeds the Bhagirathi.
Do Not Confuse With
- Cirque and arete Hollow versus ridge
- Drumlin and esker Oval hill versus winding ridge
- Till and outwash Unsorted versus sorted deposit
Memory Hook
Ice scoops cirques, shaves arêtes, sharpens horns; drops moraines, drumlins, eskers when it melts.
Mains Angle
Questions ask about glacial features and Himalayan glaciers. These points add depth.
- Erosion Cirque to U-valley
- Deposition Moraines and drumlins
- Hazards Retreat and GLOFs
A Question You May Face
An original practice question, not a past paper question.
“Describe the erosional and depositional features of glaciers and discuss the importance of Himalayan glaciers for India.”
How to Answer
- Types Valley and ice sheet.
- Features Erosional and depositional.
- India Rivers and water.
- Hazards GLOFs.
GS Relevance
Frequently Asked Questions
What are glacial landforms?
Glacial landforms are those made by moving ice. Erosional ones include cirques, arêtes, horns, U-shaped valleys, hanging valleys and fjords, while depositional ones include moraines, drumlins, eskers, kames, erratics and outwash plains, all of which are best seen in mountain valleys and in northern lands.
What is a cirque?
A cirque, also called a corrie or cwm, is an armchair-shaped hollow with steep walls at the head of a glacier valley. It is carved by ice and frost action and often holds a small lake called a tarn after the ice melts.
How does a U-shaped valley differ from a V-shaped valley?
A V-shaped valley is cut by a river that erodes downward, so it has steep sides narrowing to the bottom. A U-shaped valley is cut by a glacier, which erodes sideways and downward, leaving wide, steep walls and a flat floor.
What is a moraine?
A moraine is a ridge or sheet of rock debris carried and deposited by a glacier. Types include terminal moraines at the glacier's end, lateral moraines on its sides, medial moraines where glaciers join, and ground moraines of till spread under the ice.
Which are the major glaciers of India?
The Siachen Glacier in the Karakoram, about 70 km long, is the longest in India. Others include the Gangotri glacier in Uttarakhand, the source of the Bhagirathi, the Zemu glacier in Sikkim, and the Pindari and Milam glaciers in Uttarakhand.
PYQ Practice — Statement Analysis
1 A U-shaped valley is a feature of glacial erosion.
Glaciers widen and deepen valleys.
2 A drumlin is a winding ridge of sand deposited in an ice tunnel.
That is an esker; a drumlin is an oval hill of till.
3 The Matterhorn is a horn formed by glacial erosion.
Several cirques cut back to form it.
4 The Gangotri glacier is the source of the Bhagirathi river.
The Bhagirathi is a headstream of the Ganga.
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