GeographyISC Class 12 · Structure of India: Geological Formation, Relief and Drainage

Geological Evolution of India and the Himalayan Mountain Complex (ISC Class 12)

Updated 17 October 2026 · Fact-checked

India's oldest block is the Peninsular Plateau, a stable part of Gondwanaland made of Precambrian crystalline rocks. The Himalayas are young fold mountains raised from the sediments of the Tethys Sea when the Indian plate pushed north into the Eurasian plate, and the Great Plains are the alluvium-filled trough between them. The Himalayas form three parallel ranges (Greater, Lesser and Outer) and are divided west to east into the Kashmir, Kumaon, Nepal and Assam Himalayas.

Understand Geological Evolution of India and the Himalayan Mountain Complex

1. Geological eras. The standard eras from oldest to youngest are Precambrian (Archaean and Proterozoic), Palaeozoic, Mesozoic and Cenozoic (Tertiary and Quaternary). Indian geology uses its own divisions: Archaean (the oldest crystalline rocks such as gneiss and schist, and the Dharwar system with iron ore), Purana (the Cuddapah and Vindhyan systems), Dravidian (Palaeozoic) and Aryan (from the Upper Carboniferous: the Gondwana system with coal, the Deccan Trap lavas of the Cretaceous, the Tertiary formations of the Himalayas and the Quaternary alluvium of the plains).

2. Evolution of the Peninsular Plateau. It belongs to the ancient southern continent Gondwanaland and is a rigid, stable block of very old Precambrian crystalline rocks. When Gondwanaland broke up, the Indian plate drifted north. At the end of the Cretaceous, fissure eruptions spread basalt over the north-western Deccan (the Deccan Trap). Faulting made rift valleys such as the Narmada and the Tapi, and long erosion wore the surface into a low, rounded plateau with residual hills like the Aravallis.

3. Evolution of the Himalayas. A long, narrow sea, the Tethys, lay between Angaraland in the north and Gondwanaland in the south and collected thick sediments from both. As the Indian plate moved north and pushed beneath the Eurasian plate, the sediments were compressed and folded into mountains, uplifted in several phases during the Tertiary. The movement continues, so the Himalayas are still rising and the region has frequent earthquakes and landslides.

4. Evolution of the Great Plains. As the Himalayas rose, a long depression formed between them and the Peninsula. Rivers from both sides filled it with alluvium through the Quaternary, to a depth of thousands of metres, producing flat fertile plains.

5. Peninsular Plateau versus Himalayas.

Age: Precambrian (very old) versus Tertiary (young).
Origin: stable block of Gondwanaland versus folded Tethys sediments.
Rocks: igneous and metamorphic (granite, gneiss, basalt) versus folded and faulted sedimentary rocks.
Relief: low, worn-down, flat-topped with rounded hills (average 600 to 900 m) versus lofty rugged peaks above 8,000 m with deep valleys.
Stability: few earthquakes versus frequent earthquakes and landslides.
Rivers: old, seasonal, broad shallow valleys versus young, perennial, gorges and V-shaped valleys.
Resources: minerals versus forests, hydel potential and glaciers.

6. Structure of the Himalayas. They form a series of parallel ranges (an orthoclinal structure) running about 2,400 km from the Indus to the Brahmaputra and convex to the south.

Greater Himalayas (Himadri): the northernmost and highest, average about 6,000 m, snow-covered, with a granite core; Everest lies in Nepal and Kanchenjunga (about 8,586 m) is India's highest peak.
Lesser Himalayas (Himachal): 3,700 to 4,500 m, with ranges such as the Pir Panjal and Dhauladhar, hill stations (Shimla, Mussoorie, Darjeeling) and valleys like Kashmir and Kullu.
Outer Himalayas (Shiwaliks): the southernmost and lowest, 900 to 1,100 m, built of unconsolidated river deposits, with longitudinal valleys called duns (for example Dehradun).
Trans-Himalayas lie north of the Greater Himalayas: the Karakoram (K2, about 8,611 m), Ladakh and Zaskar ranges.

7. Offshoots. In the north-west the Hindu Kush and Sulaiman ranges run beyond India. In the north-east, after the Dihang gorge, the mountains turn south as the Purvanchal: the Patkai Bum, Naga hills, Manipur hills and Mizo (Lushai) hills along the Myanmar border. The Garo, Khasi and Jaintia hills of Meghalaya are a detached part of the Peninsular block.

8. Western versus Eastern Himalayas. The western part is wider and rises gradually from the plains; the eastern is narrower and rises abruptly. The west is drier with conifer forests and alpine pastures; the east gets very heavy rain and has dense evergreen and broad-leaved forests.

9. Regional divisions, west to east. Kashmir or Punjab Himalayas between the Indus and the Sutlej; Himachal/Uttaranchal or Kumaon Himalayas between the Sutlej and the Kali; Nepal Himalayas between the Kali and the Tista; Assam Himalayas between the Tista and the Dihang.

Geological Evolution of India and the Himalayan Mountain Complex: key facts

Standard eras: $P r ec amb r ian ∣ P a l a eoz o i c ∣ M esoz o i c ∣ C e n oz o i c (T er t ia r y, Q u a t er na r y)$
Indian divisions: Archaean
Purana (Cuddapah, Vindhyan)
Dravidian
Aryan (Gondwana, Deccan Trap, Tertiary, Quaternary)
Himalayan ranges: $G r e a t er (ab o u t 6, 000 m) ∣ L esser (3, 700 - 4, 500 m) ∣ S hi w a l ik s (900 - 1, 100 m)$
Regional Himalayas by rivers: $K a s hmi r : I n d u s - S u tl e j ∣ K u ma o n : S u tl e j - K a l i ∣ N e p a l : K a l i - T i s t a ∣ A ss am : T i s t a - D ihan g$
Formation chain: $T e t h y sse d im e n t s + pl a t eco l l i s i o n = H ima l a y a s ∣ F or e d ee p + a l l uv i u m = G r e a tP l ain s$

How to answer Geological Evolution of India and the Himalayan Mountain Complex questions

For comparison and evolution questions, use a point-by-point table and a cause-effect chain.

1Fix the headings of the comparison (age, origin, rocks, relief, stability, rivers).
2Write one clear point for each heading on both sides; do not repeat the same idea.
3For evolution, name the starting condition (Tethys Sea or Gondwanaland), the force (plate movement) and the result (landform).
4Add one named example (Everest, Kanchenjunga, Dehradun, Deccan Trap).
5Check the number of points against the marks: usually one point per mark.

Geological Evolution of India and the Himalayan Mountain Complex 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.

Earthquake risk in a hill town

Suppose a family must choose between building a house in a hill town on the Lesser Himalayas and another in a town on the Deccan Plateau. A neighbour says that both regions are equally safe from tremors.

Using the geological evolution of the two regions, decide whether the neighbour is correct and give two reasons.

Try it first, then show the solutionSolution

The Himalayas are young fold mountains whose rocks are still being pushed up by the northward movement of the Indian plate, so earthquakes and landslides are frequent.
The Peninsular Plateau is an old, rigid, stable block, with fewer earthquakes.

Answer: No. The Himalayan region is unstable and still rising; the Deccan is stable.

Memory hook: Young mountains are restless; old plateaus are calm.

Finding fossils of a vanished sea

Suppose a student on a trek in the Himalayas finds a rock containing sea shells at a very high altitude and asks how a sea animal can lie so high up.

Explain the finding using the Tethys Sea.

Try it first, then show the solutionSolution

The area was once the floor of the Tethys, which gathered thick sediments.
The collision of the Indian and Eurasian plates folded and lifted those sediments into mountains.

Answer: Marine sediments of the Tethys were folded and uplifted, so sea shells now lie in the high mountains.

Memory hook: Tethys sea floor to Himalayan roof.

Tricks to remember Geological Evolution of India and the Himalayan Mountain Complex

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

H-H-S from north to south
Himadri (Greater), Himachal (Lesser), Shiwaliks (Outer): high, middle, low from north to south.
Use it when: Ranges of the Himalayas.
Gondwana gives the plateau, Tethys gives the mountains
Peninsula = old Gondwana block; Himalayas = folded Tethys sediments; plains = alluvium in the gap.
Use it when: Evolution questions.
In river order: I-S-K-T-D
Indus, Sutlej, Kali, Tista, Dihang mark the four regional Himalayas (Kashmir, Kumaon, Nepal, Assam) in that order.
Use it when: Regional divisions.

Geological Evolution of India and the Himalayan Mountain Complex: solved examples

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

Example 1: Ranges of the Himalayas · 2 marks · Short answerBoard level

Name the three parallel ranges of the Himalayas from north to south and give the average height of the northernmost range.

Try it first, then show the solutionSolution

From north to south: Greater Himalayas (Himadri), Lesser Himalayas (Himachal), Outer Himalayas (Shiwaliks).
The Greater Himalayas average about 6,000 m.

Answer: Himadri, Himachal, Shiwaliks; Himadri about 6,000 m.

Example 2: Dun valleys · 2 marks · Short answerBoard level

What are duns? Name one example and the range in which it lies.

Try it first, then show the solutionSolution

Duns are longitudinal valleys in the Outer Himalayas, filled with unconsolidated river deposits.
Example: Dehradun, in the Shiwaliks.

Answer: Longitudinal valleys of the Shiwaliks; for example Dehradun.

Example 3: Evolution of the Himalayas · 4 marks · Long answerHarder board level

Describe the evolution of the Himalayas under three heads: the Tethys, the plate movement and the present stage.

Try it first, then show the solutionSolution

Tethys: a long narrow sea between Angaraland in the north and Gondwanaland in the south collected thick sediments from both sides.
Plate movement: the Indian plate moved north and pushed beneath the Eurasian plate, so the sediments were compressed and folded and uplifted in several phases in the Tertiary.
Present stage: the northward movement continues, so the mountains are still rising and earthquakes and landslides occur.
Result: young fold mountains of sedimentary rock with lofty peaks and deep valleys.

Answer: Tethys sediments were folded and lifted in the Tertiary by the northward push of the Indian plate under Eurasia; the rise continues today.

Example 4: Western and Eastern Himalayas · 3 marks · Short answerHarder board level

Distinguish between the Western and Eastern Himalayas on the basis of (a) width and rise, (b) rainfall, (c) natural vegetation.

Try it first, then show the solutionSolution

(a) Western: wide, rising gradually from the plains; Eastern: narrower, rising abruptly.
(b) Western: drier; Eastern: very heavy rainfall.
(c) Western: coniferous forests and alpine pastures; Eastern: dense evergreen and broad-leaved forests.

Answer: Western Himalayas are wider, drier and have conifers and pastures; Eastern Himalayas are narrower, wetter and have dense evergreen forest.

Example 5: Reasoned comparison · 4 marks · Long answerHOTS / competency

Case: A student says, "The Aravallis are older than the Himalayas, so they must be taller." (a) State whether the first part is true. (b) Explain why the conclusion is wrong, using weathering. (c) Name the highest point of the Aravallis.

Try it first, then show the solutionSolution

(a) True. The Aravallis are among the oldest fold mountains, a residual part of the Peninsular block, while the Himalayas are young Tertiary mountains.
(b) The conclusion is wrong because the Aravallis have suffered long erosion and are now low, worn-down hills; the young Himalayas have not been worn down and are still rising.
(c) Guru Shikhar, near Mount Abu.

Answer: Age does not mean height: long erosion lowered the Aravallis (highest point Guru Shikhar), while the young Himalayas are still rising.

Where students lose marks in Geological Evolution of India and the Himalayan Mountain Complex

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

Mistake: Writing the Himalayas as old fold mountains
The Aravallis and the Peninsula are ancient; the Himalayas are Tertiary.
Do this: Write young fold mountains of the Tertiary period, still rising.
Usually costs: 1 mark.
Mistake: Listing Himalayan ranges south to north or mixing names
Himadri, Himachal and Shiwaliks are swapped with the Purvanchal.
Wrong working
Outer Himalayas = Himadri
Right working
Outer Himalayas = Shiwaliks; Greater = Himadri
Do this: Remember north to south: Greater, Lesser, Outer.
Usually costs: 1 to 2 marks.
Mistake: Comparison without matching headings
Answers give a paragraph on each region instead of paired points.
Do this: Draw a two-column table with the same heading in each row.
Usually costs: 1 to 2 marks.
Mistake: Forgetting the Tethys in the evolution answer
The origin of the sediments is left out.
Do this: Always start with the Tethys Sea between Angaraland and Gondwanaland.
Usually costs: 1 mark.

Exam tips

Draw a quick sketch of the three ranges with the average heights marked.
Use the words Tethys, Gondwanaland, Angaraland and plate in every evolution answer.
Match the number of comparison points to the marks.
Plains, rivers, coasts and islands of this chapter have their own topic pages; do not mix them into a Himalayan answer.

Practice questions on Geological Evolution of India and the Himalayan Mountain Complex

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 northernmost and highest range of the Himalayas is the:
(a) Shiwaliks
(b) Himachal
(c) Himadri
(d) Purvanchal
Hint
Greater Himalayas.
Answer
(c) Himadri.
Q2 · 3 marks · Short answerHarder board level
The Peninsular Plateau is called a stable block while the Himalayas are unstable. Account for the difference in earthquake activity in three points.
Hint
Rigid block versus folding and plate push.
Answer
The Plateau is an old rigid part of Gondwanaland and has not been folded, so earthquakes are few. The Himalayas are young folded sediments, and the Indian plate still pushes into Eurasia, so they keep rising. This continuing movement causes frequent earthquakes and landslides.
Q3 · 3 marks · Short answerHarder board level
Explain how the Great Plains of north India were formed.
Hint
Depression, rivers, alluvium.
Answer
As the Himalayas rose, a long trough formed between them and the Peninsula. Rivers from the Himalayas and the Peninsula filled it with alluvium through the Quaternary to a depth of thousands of metres, making flat fertile plains.
Q4 · 4 marks · Long answerHarder board level
Name the regional divisions of the Himalayas from west to east and state the two rivers that bound each.
Hint
Indus to Dihang.
Answer
Kashmir or Punjab Himalayas (Indus-Sutlej); Himachal/Uttaranchal or Kumaon Himalayas (Sutlej-Kali); Nepal Himalayas (Kali-Tista); Assam Himalayas (Tista-Dihang).
Q5 · 1 mark · Assertion-reasonHOTS / competency
Assertion (A): The Meghalaya hills are not part of the Himalayan offshoots, although they lie close to the Himalayas.
Reason (R): The Garo, Khasi and Jaintia hills are a detached part of the Peninsular block.
(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
Which block do they belong to?
Answer
(a).

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.Which sea lay between Angaraland and Gondwanaland?Show answer
The Tethys Sea.
2.Average height of the Lesser Himalayas?Show answer
About 3,700 to 4,500 m.
3.Name the highest peak of India given in the chapter.Show answer
Kanchenjunga, about 8,586 m.
4.What are the Shiwaliks made of?Show answer
Unconsolidated river deposits.
5.Which Indian geological system holds coal?Show answer
The Gondwana system (Aryan division).

Geological Evolution of India and the Himalayan Mountain Complex: frequently asked questions

Why are earthquakes common in the Himalayas?

The Indian plate keeps pushing north into the Eurasian plate, so the young mountains are still rising and the crust is unstable.

What is an orthoclinal structure?

A series of parallel mountain ranges, as in the Himalayas.

What is the Deccan Trap?

Basalt lava spread over the north-western Deccan by fissure eruptions at the end of the Cretaceous.

Which hills are the Purvanchal?

The Patkai Bum, Naga, Manipur and Mizo hills along the Myanmar border.