GeographyICSE Class 9 · Landforms of the Earth

Mountains, Plateaus and Plains: Types and Formation (ICSE Class 9 Geography)

Updated 17 October 2026 · Draft, not yet fact-checked

Mountains are classified by formation as fold (compression, e.g. Himalayas, Alps), block (faulting, e.g. Vosges) and residual (worn-down remnants, e.g. Aravallis). Plateaus are intermont (e.g. Tibet) or volcanic (e.g. Deccan); plains are structural (e.g. Great Plains of the USA) or depositional (e.g. Ganga plain).

Understand Mountains, Plateaus and Plains: Types and Formation

1. Mountains. Natural elevations rising steeply with narrow summits; a series is a range. Formation gives three types in the syllabus.

2. Fold mountains. Sediments deposited in a shallow sea (geosyncline) are squeezed by compressional forces as two plates move towards each other; layers bend into upfolds (anticlines) and downfolds (synclines). They are high, young, long ranges, often along continental edges, with marine fossils. Examples: Himalayas (Asia), Alps (Europe), Rockies (North America), Andes (South America).

3. Block mountains. When forces crack the crust along faults, the raised block between two faults is a *horst* (block mountain) and the sunken block is a *graben* (rift valley). Examples: Vosges and Black Forest (Europe), the Rhine rift valley and the Narmada valley in India.

4. Residual mountains. Remnants of older mountains or plateaus worn down by erosion; they are low with rounded tops. Examples: Aravallis, Eastern Ghats, Parasnath (India). The Appalachians of North America are old fold mountains that have been worn down, not residual mountains.

5. Plateaus. Elevated flat-topped tablelands with at least one steep side. *Intermont plateaus* lie between or within mountains (Tibetan Plateau, the Bolivian plateau). *Volcanic plateaus* are built by lava flows from fissures (Deccan Plateau, Columbia Plateau).

6. Plains. Extensive low flat lands. *Structural plains* are raised parts of the sea floor with horizontal rocks (Great Plains of the USA, Russian platform). *Depositional plains* are formed by sediments laid by rivers, wind or ice (Indo-Gangetic plain, Nile delta, loess plains).

Mountains, Plateaus and Plains: Types and Formation: key facts

Fold mountains: $C o m p r ess i o n ∣ G eosy n c l in e ∣ Y o u n g ∣ H ima l a y a s, A l p s, R oc k i es, A n d es$
Block mountains: Faulting
Horst raised
Graben sunk
Vosges, Black Forest
Residual: Eroded remnants
Low and rounded
Aravallis
Plateaus and plains: Intermont Tibet
Volcanic Deccan
Structural Great Plains
Depositional Ganga plain

Intermont	Tibet
Volcanic	Deccan
Structural	Great Plains
Depositional	Ganga plain

Mountains, Plateaus and Plains: Types and Formation 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.

Sandwiched pile

Suppose a student pushes the two ends of a stack of cloth sheets together and sees the middle fold up into waves.

Relate it to mountain building.

Try it first, then show the solutionSolution

Cloth layers are like sediment layers.
Pushing from the sides is compression.
The waves are folds forming fold mountains.

Answer: Compression of layers forms fold mountains.

Memory hook: Push from sides: folds.

Tricks to remember Mountains, Plateaus and Plains: Types and Formation

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

HG = Horst Goes up, Graben Goes down
Horst up, graben down.
Use it when: Block mountains.
Old = rounded
Residual mountains are old and rounded.
Use it when: Residual.

Mountains, Plateaus and Plains: Types and Formation: solved examples

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

Example 1: Name · 4 marks · Short answerBoard level

Give one example each of (a) fold mountain, (b) block mountain, (c) residual mountain, (d) volcanic plateau. [4]

Try it first, then show the solutionSolution

(a) Himalayas.
(b) Vosges.
(c) Aravallis.
(d) Deccan.

Answer: (a) Himalayas (b) Vosges (c) Aravallis (d) Deccan plateau.

Example 2: Horst and graben · 3 marks · Short answerHarder board level

Two parallel cracks appear in the crust and the middle block slides down while the outer blocks stay. Name the feature formed and the features left on either side, and say what forces may cause this. [3]

Try it first, then show the solutionSolution

Forces crack the crust along parallel faults.
The land between faults sinks, forming a rift valley.
Land on either side stands as a block mountain.

Answer: A rift valley (graben) forms in the middle with block mountains (horsts) on either side, caused by tensional or compressional forces along faults.

Example 3: Why Himalayas are young · 3 marks · Short answerHarder board level

Why are the Himalayas high and rugged while the Aravallis are low and rounded? [3]

Try it first, then show the solutionSolution

The Himalayas are young and still rising.
Erosion has not worn them down.
The Aravallis are very old and have been eroded for ages.

Answer: Young and rising versus old and eroded.

Example 4: Plains compare · 4 marks · Long answerHarder board level

Compare structural and depositional plains with an example each. [4]

Try it first, then show the solutionSolution

Structural: uplifted sea floor with horizontal rocks (Great Plains).
Depositional: built by sediment deposits (Ganga plain).
Structural are of rock; depositional are of alluvium.
Structural are broad and level; depositional are fertile.

Answer: Structural plains: uplifted rock layers; depositional plains: river-laid alluvium.

Example 5: Case: the marine fossil · 5 marks · Case-basedHOTS / competency

Case. A trekker finds fossils of sea shells at 4,000 m in a mountain range. (i) Name the mountain type. [1] (ii) What does the fossil show? [1] (iii) Explain how they reached there. [2] (iv) Name another example. [1]

Try it first, then show the solutionSolution

(i) Fold mountain.
(ii) The rocks were once under the sea.
(iii) Sediments in a geosyncline were compressed and uplifted.
(iv) Alps or Andes.

Answer: (i) Fold mountain (ii) Marine origin (iii) Compression and uplift (iv) Alps.

Where students lose marks in Mountains, Plateaus and Plains: Types and Formation

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

Mistake: Writing the Himalayas as block mountains
Type confusion.
Do this: Himalayas are fold mountains.
Usually costs: 1 mark.
Mistake: Using horst for rift valley
Terms swapped.
Do this: Horst up, graben down.
Usually costs: 1 mark.
Mistake: Forgetting examples
Name only type.
Do this: Add one example each.
Usually costs: 1 mark.

Exam tips

Draw simple diagrams of folding and faulting.
Give examples from the syllabus lists.
Link each landform to its formation process.
Use the words young and old for mountains.

Practice questions on Mountains, Plateaus and Plains: Types and Formation

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
The Tibetan Plateau is a/an:
(a) volcanic plateau
(b) intermont plateau
(c) residual plateau
(d) coastal plateau
Hint
Between mountains.
Answer
(b) intermont plateau.
Q2 · 2 marks · Very short answerBoard level
Define a plateau. [2]
Hint
Tableland.
Answer
A raised flat-topped tableland with at least one steep side.
Q3 · 2 marks · Very short answerBoard level
Name two depositional plains. [2]
Hint
Rivers.
Answer
The Indo-Gangetic plain and the Nile delta.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Fold mountains often contain marine fossils.
Reason (R): They form from sediments laid in seas.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Geosyncline.
Answer
(a).
Q5 · 3 marks · Short answerHarder board level
Describe a volcanic plateau and its soil. [3]
Hint
Basalt.
Answer
Formed by lava flows from fissures, as the Deccan Plateau; weathering of basalt gives black cotton soil.
Q6 · 2 marks · Very short answerBoard level
Distinguish a horst from a graben. [2]
Hint
Up/down.
Answer
A horst is a raised block between faults; a graben is a sunken block.
Q7 · 3 marks · Short answerHarder board level
Why are plains densely populated? Give two reasons. [3]
Hint
Fertile.
Answer
Fertile soil supports agriculture and flat land is suitable for transport and settlements.
Q8 · 3 marks · Short answerHarder board level
Compare fold and residual mountains on age, height and shape. [3]
Hint
Table.
Answer
Fold: young, high, jagged; residual: old, low, rounded.
Q9 · 3 marks · Case-basedHOTS / competency
Case. A geologist finds a narrow valley with steep walls between two parallel mountain blocks. (i) Name the valley. [1] (ii) Name the forces. [1] (iii) Give an example. [1]
Hint
Rift.
Answer
(i) Rift valley (graben). (ii) Faulting by tension (or compression). (iii) Rhine valley.
Q10 · 3 marks · Long answerHOTS / competency
Case. A student says the Deccan plateau and the Tibetan plateau have the same origin. Evaluate. [3]
Hint
Different.
Answer
Incorrect: the Deccan is a volcanic plateau made of lava; Tibet is an intermont plateau uplifted among mountains.

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.Raised block between faults?Show answer
Horst.
2.Himalayas are what type?Show answer
Fold mountains.
3.Deccan plateau type?Show answer
Volcanic.
4.Upfold name?Show answer
Anticline.
5.Great Plains are?Show answer
Structural plains.

Mountains, Plateaus and Plains: Types and Formation: frequently asked questions

Are volcanic mountains in the syllabus?

The syllabus lists fold, block and residual mountains.

What is a tableland?

Another name for a plateau.

What is a geosyncline?

A long shallow sea trough filled with sediment.