GeographyISC Class 11 · Glacial Landforms

Glaciers, Types, Erosion and Erosional Landforms (ISC Class 11 Geography)

Updated 17 October 2026 · Fact-checked

A glacier forms where snow exceeds melt and compacts to firn and then ice; continental glaciers (Antarctica, Greenland) differ from mountain or valley glaciers (Gangotri). Ice erodes by plucking, abrasion and attrition, carving cirques with tarns, aretes, horns, U-shaped and hanging valleys, and fjords.

Understand Glaciers, Types, Erosion and Erosional Landforms

Formation. Snow above the snowline piles up; the weight presses it into firn (neve) and then dense bluish ice, which flows downslope under gravity by internal deformation and sliding on a film of meltwater, from a few centimetres to a few metres a day. The valley centre moves faster than sides and base. The accumulation zone is the upper part; the ablation zone is where ice is lost; the end is the snout.

Types. Continental glaciers (ice sheets; ice caps on plateaus) cover Antarctica and Greenland. Mountain or valley glaciers flow down valleys (Himalayas, Alps, Rockies); piedmont glaciers spread on plains.

Erosion. Plucking tears away blocks after meltwater refreezes in joints. Abrasion scratches and polishes bedrock with embedded rock (striations, rock flour). Attrition breaks the load into smaller pieces. Debris travels on, in and under the ice; erratics are boulders dropped on different rock.

Erosional landforms.

Cirque (corrie, cwm): armchair-shaped hollow at a valley head; a lake in it is a tarn.
Arete: knife-edged ridge between two cirques.
Horn: pyramidal peak where three or more cirques cut back (Matterhorn).
Col: pass where two cirque walls cut through an arete.
U-shaped valley: glacier-widened trough with truncated spurs.
Hanging valley: tributary valley left high above the main trough, often with a waterfall.
Fjord: deep, long, narrow inlet in a glacial trough drowned by the sea (Norway, Chile, New Zealand, Greenland).
Roches moutonnees: smoothed upstream side, plucked downstream side.

India. Gangotri (Gaumukh is the source of the Bhagirathi), Siachen, Zemu and Pindari.

Glaciers, Types, Erosion and Erosional Landforms: key facts

Glacier formation: Snow
Firn (neve)
Glacier ice
Glacial erosion: $P l u c k in g ∣ A b r a s i o n ∣ A tt r i t i o n$
Erosional landforms: Cirque and tarn
Arete
Horn
Col
U-shaped valley
Hanging valley
Fjord
Rate: $R a t e = d i s t an ce / t im e ∣ C o n v er tt o a co mm o n u ni t$

How to answer Glaciers, Types, Erosion and Erosional Landforms questions

Questions ask for formation (4 marks) or a named landform with a sketch in words.

1Define the landform and name the process.
2Give the cause in numbered stages.
3State a place or an Indian example.
4For movement sums, convert units first.

Glaciers, Types, Erosion and Erosional Landforms in real life

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

Frozen scoop

Suppose a block of ice is dragged slowly across a wooden board with sand and pebbles stuck in its base.

What marks appear and which glacial process do they model?

Try it first, then show the solutionSolution

Parallel scratches appear on the board.
This models abrasion leaving striations.

Answer: Abrasion; striations.

Memory hook: Sandpaper made of ice.

Speed of a boulder

Suppose a glacier surface boulder moves 0.15 m each day.

How far does it move in a year of 365 days, and how many years to travel 1 km?

Try it first, then show the solutionSolution

0.15 x 365 = 54.75 m per year.
1,000 / 54.75 = 18.26 years.

Answer: 54.75 m a year; about 18.3 years for 1 km.

Memory hook: Daily speed times 365.

Tricks to remember Glaciers, Types, Erosion and Erosional Landforms

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

CAH
Cirque, Arete, Horn: eroding backwards from the head.
Use it when: Landform order.
U-trough fills, V-valley cuts
Glaciers fill and widen (U); rivers cut down (V).
Use it when: Valley shapes.

Glaciers, Types, Erosion and Erosional Landforms: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Peak identification · 1 mark · MCQBoard level

A pyramidal peak formed by three or more cirques is a:
(a) arete
(b) horn
(c) col
(d) drumlin

Try it first, then show the solutionSolution

Matterhorn.

Answer: (b) Horn.

Example 2: Types of glacier · 3 marks · Short answerBoard level

Name the two main types of glacier and one example of each region.

Try it first, then show the solutionSolution

Continental glaciers (ice sheets): Antarctica or Greenland.
Mountain or valley glaciers: Gangotri or Siachen.
Piedmont glaciers spread on plains.

Answer: Continental (Antarctica) and mountain (Gangotri).

Example 3: Movement difference · 4 marks · Long answerHarder board level

A valley glacier moves 2.5 m a day at its centre and 1.0 m a day near its sides. Find the difference in 20 days and explain why it exists.

Try it first, then show the solutionSolution

Centre in 20 days: 2.5 x 20 = 50 m.
Side in 20 days: 1.0 x 20 = 20 m.
Difference = 50 - 20 = 30 m.
Friction with the valley walls and bed slows the sides and base.

Answer: 30 m; friction holds back the sides.

Example 4: Cirque formation · 4 marks · Long answerHarder board level

Explain how a cirque forms and how a tarn arises.

Try it first, then show the solutionSolution

Snow collects in a hollow on a mountainside and turns to ice.
Freeze-thaw and plucking steepen the back wall.
Abrasion deepens the floor as the ice rotates, forming an armchair hollow.
When the ice melts, water collects in the basin as a tarn.

Answer: Snow hollow plucked and abraded into an armchair; the basin holds a tarn.

Example 5: Interpret a landscape · 5 marks · Case-basedHOTS / competency

Case: A mountain region shows a knife-edged ridge between two bowl-shaped hollows with lakes, a flat-floored trough below, and a waterfall from a high side valley. (a) Name the landforms. (b) Say which process formed the trough. (c) Explain why the side valley hangs.

Try it first, then show the solutionSolution

(a) Arete, cirques with tarns, U-shaped valley, hanging valley.
(b) Glacial erosion by a valley glacier widening a river valley.
(c) The tributary glacier was smaller, so it cut less deeply than the main glacier.

Answer: (a) Arete, cirques/tarns, U-valley, hanging valley (b) glacial erosion (c) smaller tributary glacier cut less deeply.

Where students lose marks in Glaciers, Types, Erosion and Erosional Landforms

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

Mistake: Calling an arete a valley
Landform categories are confused.
Do this: An arete is a sharp ridge between cirques.
Usually costs: 1 mark.
Mistake: Confusing plucking with abrasion
Tearing and scraping are treated as one process.
Do this: Plucking removes blocks from joints; abrasion scrapes and polishes with embedded rock.
Usually costs: 1 mark.
Mistake: Rate sums without unit conversion
Days and years are mixed.
Wrong working
0.3 x 200 = 6
Right working
0.3 m/day x 200 days = 60 m
Do this: Convert to the same unit first.
Usually costs: 1 mark.

Exam tips

Define firn in the formation chain.
Use striations as evidence of ice movement.
Mention the Matterhorn for horns.
Name Indian glaciers: Gangotri, Siachen, Zemu, Pindari.

Practice questions on Glaciers, Types, Erosion and Erosional Landforms

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

Q1 · 1 mark · MCQBoard level
Parallel scratches on bedrock caused by glaciers are called:
(a) erratics
(b) striations
(c) tarns
(d) eskers
Hint
Abrasion marks.
Answer
(b) Striations.
Q2 · 3 marks · Short answerHarder board level
A glacier surface moves 0.3 m a day. How far does it travel in 200 days, and how long to travel 100 m?
Hint
Rate times time.
Answer
0.3 x 200 = 60 m. Time for 100 m = 100 / 0.3 = 333.3 days, about 333 days.
Q3 · 4 marks · Long answerHarder board level
Explain how a fjord forms and where fjords occur.
Hint
Over-deepened trough drowned by the sea.
Answer
A glacier over-deepens a U-shaped valley below sea level; when ice melts and sea level rises, the sea floods the trough, forming a long narrow inlet. Fjords occur in Norway, southern Chile, New Zealand and Greenland.
Q4 · 3 marks · Short answerHarder board level
Distinguish between plucking and abrasion.
Hint
Tearing blocks versus scraping.
Answer
Plucking tears away blocks of rock when meltwater refreezes in joints and the moving ice drags them off; abrasion scrapes and polishes bedrock with embedded fragments, leaving striations.
Q5 · 4 marks · Case-basedHOTS / competency
Case: A glaciated valley, now free of ice, has a broad trough with a stream running in a narrow V-shaped gorge cut into its floor. (a) Name the shape of the glacial valley. (b) Explain the V-shaped feature inside it. (c) Name two erosional landforms found at the valley head.
Hint
U-shaped trough.
Answer
(a) U-shaped valley. (b) A river has taken over after the ice melted and cut down into the floor. (c) Any two of: cirque, arete, horn.

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.Water-filled cirque?Show answer
Tarn.
2.Source of Bhagirathi?Show answer
Gaumukh, snout of Gangotri glacier.
3.Knife-edged ridge?Show answer
Arete.
4.Glacier ice before ice?Show answer
Firn.
5.Long inlet in glacial trough?Show answer
Fjord.

Glaciers, Types, Erosion and Erosional Landforms: frequently asked questions

Why does the centre move faster?

Friction slows the sides and base.

Where is plucking strongest?

On the downstream side of obstacles and at the glacier head.

Are Himalayan valleys U-shaped?

At high altitude yes; lower down they are V-shaped.