Glacial Landforms: Glaciers, Glacial Erosion, Cirques and Moraines, ISC Class 11

What Glacial Landforms is about

Weightage: CISCE gives no Class XI unit weightage for ISC Geography. Glacial Landforms is topic 9 of the Class XI syllabus (Changing Face of the Earth) and can be asked anywhere in the 70-mark Paper I (Theory, 3 hours). Class XI is examined by the school, so your school sets the paper and decides how many marks each topic carries.Source: CISCE ISC Geography (853) syllabus, examination year 2028, Class XI

Key concepts

Glaciers: formation and types

Formation
1. Snow accumulates above the snowline, where winter snowfall exceeds summer melting.
2. The weight of new snow presses older layers into firn (neve) and then into dense, bluish glacier ice.
3. When the ice is thick enough, it begins to flow downslope under gravity, partly by internal deformation of the ice and partly by sliding over its bed on a film of meltwater.
4. Movement is slow: from a few centimetres to a few metres a day; the centre of a valley glacier moves faster than its sides and base, which are held back by friction.

Zones: the accumulation zone (upper, where snow is added) and the ablation zone (lower, where ice is lost by melting and evaporation). The lower end of a glacier is its snout.

Types
1. Continental glaciers (ice sheets): vast sheets of ice, often more than a kilometre thick, that bury whole landscapes and flow outward from the centre; today they cover Antarctica and Greenland. Small ice sheets on high plateaus are called ice caps.
2. Mountain or valley glaciers: tongues of ice that flow down mountain valleys from snowfields, as in the Himalayas, the Alps and the Rockies. Where several valley glaciers spread out and merge on a plain at the foot of mountains, they form a piedmont glacier.

Worked example

[4] Distinguish between continental glaciers and valley glaciers. (Understanding)

Try it first, then show the solutionSolution

1. Continental: vast ice sheets over large land areas - 1 mark.
2. Continental: flow outward from the centre; Antarctica, Greenland - 1 mark.
3. Valley: tongues of ice confined to mountain valleys - 1 mark.
4. Valley: flow downslope; Gangotri, Siachen in the Himalayas - 1 mark.

Answer: Continental glaciers are vast sheets of ice that cover large land areas, burying the relief and flowing outward from the centre in all directions, as in Antarctica and Greenland. Valley glaciers are long tongues of ice confined to mountain valleys, flowing downslope from snowfields, as with the Gangotri and Siachen glaciers of the Himalayas and Karakoram.

Processes of glacial erosion

Glaciers are powerful agents of erosion because of the great weight of the ice and the rock debris frozen into it.

1. Plucking (quarrying): meltwater seeps into joints and cracks of the bedrock and refreezes, binding the rock to the ice. As the glacier moves, it tears away blocks of rock. Plucking is strongest on the downstream (lee) side of rock obstacles and at the head of a glacier.
2. Abrasion: rock fragments embedded in the base and sides of the ice act like a giant file or sandpaper, scraping, grinding and polishing the bedrock. It leaves parallel scratches called striations, which show the direction of ice movement, and grinds rock into fine rock flour.
3. Attrition: the debris carried by the glacier is rubbed and crushed against itself and the bed, breaking into smaller fragments.

Freeze-thaw (frost) weathering on the valley sides above the glacier supplies extra debris that falls onto the ice.

Transport: debris is carried on the surface (supraglacial), within the ice (englacial) and at the base (subglacial). Ice can carry boulders of any size; boulders carried far and dropped on different rock are called erratics.

Worked example

[4] Explain plucking and abrasion as processes of glacial erosion. (Recall)

Try it first, then show the solutionSolution

1. Plucking: meltwater freezes in joints, binding rock to ice - 1 mark.
2. Moving ice tears out blocks of rock - 1 mark.
3. Abrasion: debris in the ice scrapes and grinds bedrock - 1 mark.
4. Leaves striations and rock flour - 1 mark.

Answer: In plucking, meltwater enters joints in the bedrock and refreezes, so the rock becomes attached to the ice and is torn away as the glacier moves. In abrasion, rock fragments embedded in the base and sides of the ice scrape and grind the bedrock like sandpaper, polishing it, cutting striations and producing fine rock flour.

Erosional landforms: cirque, arete and horn

1. Cirque (corrie or cwm): a deep, armchair-shaped hollow with a steep back wall and a rock basin, at the head of a glacial valley. It forms where snow collects in a hollow on a mountainside; freeze-thaw and plucking steepen the back wall while abrasion deepens the floor as the ice rotates. When the ice melts, water collects in the basin to form a cirque lake or tarn.
2. Arete: a sharp, knife-edged ridge left between two cirques (or two glacial valleys) that are cut back towards each other.
3. Horn (pyramidal peak): a sharp, pointed peak formed when three or more cirques erode headward into the same mountain from different sides. The Matterhorn in the Alps is the classic example; many high Himalayan peaks have horn-like forms.
4. Col: a saddle-shaped pass formed where the back walls of two cirques meet and cut through an arete.

In the Himalayas, cirques and tarns are common in the high valleys of Uttarakhand, Himachal Pradesh and Ladakh.

Worked example

[4] Explain the formation of a cirque. (Understanding)

Try it first, then show the solutionSolution

1. Snow collects in a mountain hollow and turns to ice - 1 mark.
2. Plucking and frost action steepen the back wall - 1 mark.
3. Rotational movement and abrasion deepen the floor into a basin - 1 mark.
4. Armchair shape; basin later holds a tarn - 1 mark.

Answer: A cirque begins as a hollow on a mountainside where snow collects and turns to ice. Freeze-thaw and plucking cut back and steepen the back wall, while the ice rotates and abrades the floor into a rock basin. The result is a steep-sided, armchair-shaped hollow, whose basin often holds a small lake called a tarn after the ice melts.

Erosional landforms: valleys and fjords

1. U-shaped valley (glacial trough): a river valley with a V-shaped cross-section is widened and deepened by a glacier into a broad, flat-floored valley with steep sides. The glacier fills the whole valley and erodes its floor and sides, straightening it and cutting off the ends of spurs to form truncated spurs.
2. Hanging valley: a smaller tributary glacier cannot deepen its valley as much as the main glacier. When the ice melts, the floor of the tributary valley is left hanging high above the main valley floor, often with a waterfall.
3. Fjord: a deep, long, narrow arm of the sea occupying a U-shaped glacial valley that was over-deepened below sea level and later drowned when the sea level rose after the ice age. Fjords line the coasts of Norway, southern Chile, New Zealand and Greenland.
4. Roches moutonnees: rock humps smoothed by abrasion on the side facing the ice and made rough by plucking on the downstream side.

Himalayan valleys at high altitudes show U-shaped profiles; lower down, where rivers have taken over, the valleys are V-shaped.

Worked example

[4] How does a glacier change a V-shaped river valley into a U-shaped valley? (Understanding)

Try it first, then show the solutionSolution

1. The glacier fills the whole valley, not just the bed - 1 mark.
2. Abrasion and plucking erode floor and sides together - 1 mark.
3. Interlocking spurs are cut off as truncated spurs - 1 mark.
4. Result: wide, flat floor, steep sides; straighter valley - 1 mark.

Answer: Unlike a river, a glacier fills its whole valley, so plucking and abrasion act on both floor and sides at once. It deepens and widens the valley and cuts off interlocking spurs as truncated spurs, turning a narrow V-shaped valley into a straighter, broad, flat-floored U-shaped valley with steep sides.

Depositional landforms: moraines and related features

Glacial deposits are of two kinds. Till is unsorted, unstratified debris dropped directly by ice (boulders, gravel and clay mixed together). Outwash is debris sorted and laid down in layers by meltwater streams.

Moraines (ridges or sheets of till)
1. Lateral moraine: ridges along the sides of a valley glacier, formed from debris that falls from the valley walls.
2. Medial moraine: a ridge down the middle of a glacier, formed when two lateral moraines join where two glaciers merge.
3. Ground moraine: a sheet of till spread over the valley floor as a glacier melts back.
4. Terminal (end) moraine: a crescent-shaped ridge across the valley at the furthest point reached by the snout; it may dam a lake behind it.
5. Recessional moraine: ridges behind the terminal moraine, marking pauses as the glacier retreats.

Related features
1. Outwash plain: a gently sloping plain of sand and gravel spread by meltwater beyond the terminal moraine.
2. Esker: a long, winding ridge of sorted sand and gravel laid by a stream flowing in a tunnel under the ice.
3. Drumlin: a smooth, oval, egg-shaped hill of till, elongated in the direction of ice flow, with a blunt upstream end and a tapering downstream end; drumlins often occur in groups (basket of eggs topography).
4. Erratics: boulders carried far and dropped on rock of a different type.

Worked example

[4] Distinguish between lateral, medial and terminal moraines. (Analysis)

Try it first, then show the solutionSolution

1. Lateral: along the sides; debris from valley walls - 1 mark.
2. Medial: middle of the glacier; two laterals merge - 1 mark.
3. Terminal: across the valley at the snout's furthest point - 1 mark.
4. All are unsorted till; terminal may dam a lake - 1 mark.

Answer: Lateral moraines are ridges of debris along the sides of a valley glacier, fed by material falling from the valley walls. A medial moraine runs down the middle of a glacier where two lateral moraines join after two glaciers meet. A terminal moraine is a crescent-shaped ridge across the valley marking the furthest advance of the snout. All three are unsorted till.

Glacial Landforms in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Glaciers, Types, Erosion and Erosional Landforms
• Moraines, Outwash Plains, Eskers and Drumlins

Glacial Landforms: key facts

Glacier formation

Snow -> firn (neve) -> glacier ice

Above the snowline; accumulation greater than ablation.

Types

Continental (ice sheet, ice cap) vs mountain/valley (and piedmont)

Antarctica, Greenland; Gangotri, Siachen.

Erosion

$Plucking+abrasion+attrition$

Abrasion leaves striations and rock flour.

Erosional landforms

Cirque (tarn), arete, horn, col, U-shaped valley, hanging valley, fjord

Matterhorn = horn.

Depositional landforms

Moraines: lateral, medial, ground, terminal, recessional; outwash plain, esker, drumlin, erratic

Till unsorted; outwash sorted.

Rate of movement or retreat

$Rate=distance/time$

450 m in 25 years = 18 m/yr.

How the school exam asks Glacial Landforms

The question patterns to expect, and the method that works for each.

Tricks to remember Glacial Landforms

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Erosion: 'PAA'

  Plucking pulls, Abrasion abrades, Attrition grinds the load.

  Use it when: Three processes.

• Peak-making order

  One cirque makes a bowl, two make an arete, three or more make a horn.

  Use it when: Cirque, arete, horn.

• Moraines by position: 'L-M-G-T'

  Left and right side Lateral, Middle Medial, Ground on the floor, Terminal at the toe.

  Use it when: Types of moraines.

Glacial Landforms: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section D style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 8-mark question split into 2 + 2 + 3 + 1 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Glacial Landforms

The slips examiners see most often, and what to write instead.

• ✗Mistake: Calling glacial deposits sorted

  Confusing till with outwash.

  Wrong working

  Moraines are layered sand and gravel.

  Right working

  Moraines are unsorted till; only meltwater deposits are sorted.

  ✓Do this: Ice dumps; water sorts.

  Usually costs: 1 mark.

• ✗Mistake: Mixing up arete and horn

  Both form from cirques.

  ✓Do this: Two cirques give a ridge (arete); three or more give a peak (horn).

  Usually costs: 1 mark.

• ✗Mistake: Drawing the glacial valley as V-shaped

  Confusion with river valleys.

  ✓Do this: Glacial valleys are U-shaped with flat floors and steep sides.

  Usually costs: 1-2 marks.

• ✗Mistake: No Indian example

  The syllabus asks for examples from India.

  ✓Do this: Gangotri (Gaumukh, Bhagirathi), Siachen (Karakoram), Zemu (Sikkim), Pindari (Kumaon).

  Usually costs: 1 mark.

• ✗Mistake: Describing a medial moraine as lying along the sides

  Lateral and medial confused.

  ✓Do this: Medial runs down the middle where two laterals merge.

  Usually costs: 1 mark.

Practice questions on Glacial Landforms

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · Very short answerExam level

   What is a tarn?

   Hint

   Lake in a hollow.

   Answer

   A small lake occupying the rock basin of a cirque.

2. Q2 · 1 mark · Very short answerExam level

   Name the glacier from whose snout at Gaumukh the Bhagirathi emerges.

   Hint

   Uttarakhand.

   Answer

   The Gangotri glacier.

3. Q3 · 1 mark · MCQExam level

   A ridge of debris formed where two valley glaciers merge is a:
   (a) Lateral moraine
   (b) Ground moraine
   (c) Medial moraine
   (d) Terminal moraine

   Hint

   Middle.

   Answer

   (c) Medial moraine.

4. Q4 · 1 mark · Very short answerHarder exam level

   What are striations, and what do they indicate?

   Hint

   Scratches.

   Answer

   Parallel scratches cut in bedrock by debris in moving ice; they show the direction of ice movement.

5. Q5 · 4 marks · Short answerHarder exam level

   [4] Distinguish between till and outwash deposits.

   Hint

   Agent, sorting, layering, landforms.

   Answer

   (1) Till is dropped directly by ice; outwash is laid down by meltwater streams. (2) Till is unsorted, mixing boulders and clay; outwash is sorted by size. (3) Till is unstratified; outwash is layered. (4) Till forms moraines and drumlins; outwash forms outwash plains and eskers.

6. Q6 · 4 marks · Short answerHarder exam level

   [4] Explain the formation of an arete and a horn.

   Hint

   Cirques cutting back.

   Answer

   (1) Cirques erode headward, cutting back into the mountain. (2) Where two cirques cut back towards each other, the rock between them is narrowed into a knife-edged ridge, an arete. (3) Where three or more cirques cut into one mountain from different sides, a sharp pyramidal peak, a horn, is left. (4) The Matterhorn in the Alps is the classic horn.

7. Q7 · 4 marks · Short answerHarder exam level

   [4] Why does the centre of a valley glacier move faster than its sides, and what is the evidence of glacier movement on the ground?

   Hint

   Friction; marks left behind.

   Answer

   (1) The sides and base of the glacier are slowed by friction against the valley walls and bed. (2) The centre and surface, away from friction, move fastest. (3) On the ground, striations and polished rock show the direction of ice movement. (4) Erratics carried far from their source and lines of moraines also prove that ice has moved.

8. Q8 · 4 marks · Short answerHOTS / competency

   [4] A glacier moves 0.4 m a day. How far will a boulder on its surface travel in 365 days, and how many years will the boulder take to travel 1.46 km? Name the deposit it will join at the snout.

   Hint

   Distance = rate x time.

   Answer

   (1) Distance in a year = 0.4 x 365 = 146 m. (2) 1.46 km = 1,460 m. (3) Time = 1,460 / 146 = 10 years. (4) At the snout the boulder will be dropped into the terminal moraine (or onto the outwash plain if carried further by meltwater).

9. Q9 · 4 marks · Short answerHOTS / competency

   [4] 'A glaciated valley tells its story from head to snout.' Explain the sequence of landforms from the head of a valley glacier to beyond its snout.

   Hint

   Erosion upstream, deposition downstream.

   Answer

   (1) At the head: cirques with tarns, separated by aretes and crowned by horns. (2) Along the valley: a U-shaped trough with truncated spurs and hanging valleys, lined by lateral moraines (medial where glaciers join). (3) At the snout: a terminal moraine, with recessional moraines behind it, and drumlins on the floor. (4) Beyond the snout: an outwash plain of sorted sand and gravel built by meltwater; eskers mark old sub-glacial streams.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What is firn?Show answer

   Granular, partly compacted old snow, the stage between snow and glacier ice.

2. 2.Where are the two present-day continental ice sheets?Show answer

   Antarctica and Greenland.

3. 3.Which glacier lies in the Karakoram in Ladakh?Show answer

   The Siachen glacier.

4. 4.What is a fjord?Show answer

   A drowned, over-deepened glacial trough forming a long, narrow, steep-sided sea inlet.

5. 5.What is an erratic?Show answer

   A boulder carried by ice and dropped far away on rock of a different type.

6. 6.What is the lower end of a glacier called?Show answer

   The snout.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Snow -> firn -> ice; accumulation zone above, ablation zone below; snout at the lower end.
• ☐Types: continental (Antarctica, Greenland) and mountain/valley (Gangotri, Siachen, Zemu, Pindari); piedmont at mountain foot.
• ☐Erosion: plucking (refrozen meltwater tears rock), abrasion (striations, rock flour), attrition.
• ☐Cirque with tarn; two cirques -> arete; three or more -> horn (Matterhorn); col = pass.
• ☐U-shaped valley, truncated spurs, hanging valley with waterfall, fjord (Norway, Chile, New Zealand).
• ☐Moraines (unsorted till): lateral, medial, ground, terminal, recessional.
• ☐Meltwater (sorted): outwash plain, esker; drumlin = till hill shaped by ice; erratics.
• ☐Gangotri snout at Gaumukh is the source of the Bhagirathi.

Glacial Landforms: frequently asked questions