Classification of Mountains – Fold, Block and Volcanic
Geography › Mountains, Volcanoes, Earthquakes and Tsunami · Topic 4.1
Mountains are classified by the way they form into fold mountains, made by compression of rock layers, block or fault-block mountains, made by faulting that raises blocks of crust, volcanic mountains, built by lava and ash, and residual mountains, left standing when surrounding land is eroded. Fold mountains are the longest and highest, and the Aravallis are among the oldest.
5 min read · UPSC Prelims · Geography · Mountains, Volcanoes, Earthquakes and Tsunami
At a Glance
- Fold Compression of layers; Himalayas, Alps, Andes
- Block Faulting; Vosges, Black Forest, Sierra Nevada
- Volcanic Lava and ash; Fuji, Kilimanjaro, Mauna Kea
- Residual Eroded remnants; Aravalli, Vindhya, Nilgiri
- Dome Uplift by magma pressure; Black Hills
- Exam link UPSC Prelims, Geography: Mountains, Volcanoes, Earthquakes and Tsunami
Where Does It Fit?
This is the first topic of the category on mountains, volcanoes, earthquakes and tsunami. The previous category dealt with plate movements that build mountains. The next topic names the significant mountain ranges of the world. Previous topic: Great Rift Valley and Rift Valley Lakes. Next topic: Significant Mountain Ranges of the World.
What Is a Mountain?
In short: a mountain is a high, steep landform that rises well above its surroundings.
A mountain is a natural elevation of the land surface, with a limited summit area and steep slopes, rising high above the surrounding country. There is no universal rule for the height: in India, an elevation above about 600 m has traditionally been regarded as a mountain, while lower ones are hills, and a plateau is a flat-topped highland. Mountains are classified in two main ways. One is by the process that made them, giving fold, block, volcanic and residual types. The other is by age, giving young and old ranges. The forces behind them are described in Plate Tectonics and Types of Plate Boundaries.
What Are Fold Mountains?
Fold mountains are the most common and the highest type. They form when compressive forces, usually at convergent plate boundaries, squeeze thick layers of sediment and bend them into upfolds (anticlines) and downfolds (synclines), as explained in Endogenic Geomorphic Movements and Diastrophism. They form long, narrow belts and often run parallel to a coast.
- Young fold mountains formed in the Alpine orogeny, roughly in the last 65 million years: Himalayas, Alps, Andes, Rockies, Atlas. They are high, steep and rugged and are earthquake-prone.
- Old fold mountains formed hundreds of millions of years ago and have been worn down to low, rounded ranges: Aravalli, Appalachians, Urals, the Scottish Highlands.
The Aravalli range in India, with the Guru Shikhar at Mount Abu, about 1,722 m, as its highest peak, is among the oldest fold mountains of the world, formed in the Precambrian period.
What Are Block Mountains?
Block mountains, also called fault-block or horst mountains, form when large blocks of the crust are raised or lowered along faults, usually under tension. The raised block between two faults is a horst, and the lowered block is a graben, which forms a rift valley. Block mountains have steep fault scarps on the sides and a relatively flat top. Examples are the Vosges in France and the Black Forest in Germany on either side of the Rhine rift, the Sierra Nevada in California and the Wasatch Range in Utah. Peninsular India has several block structures, including the Satpura range, which is a horst between the Narmada and Tapi rift valleys.
What Are Volcanic, Dome and Residual Mountains?
| Type | Formation | Examples |
|---|---|---|
| Volcanic mountains | Built by lava and ash around a vent; may be active, dormant or extinct | Mount Fuji (Japan), Mount Kilimanjaro (Tanzania), Mount Mayon (Philippines), Mauna Kea and Mauna Loa (Hawaii), Barren Island volcano (India) |
| Dome mountains | Rising magma bulges the overlying layers upward, which are later eroded | Black Hills (USA) |
| Residual mountains | Remnants of higher land left after long erosion; also called relict | Aravalli, Vindhya, Satpura, Nilgiri, Parasnath, Girnar and Rajmahal hills |
The Western Ghats are sometimes treated as the escarpment of a faulted block, while the Nilgiris, Anamalai and others are often described as residual or block features, so textbooks may classify them differently. Volcanic mountains are discussed in Volcanism – Causes and Lava Types.
How Do the Types Compare?
| Feature | Fold | Block | Volcanic |
|---|---|---|---|
| Cause | Compression | Faulting under tension | Eruption of magma |
| Shape | Long, curved belts | Steep-sided blocks | Cone or dome |
| Hazards | Earthquakes | Earthquakes | Eruptions and lava |
| Typical rocks | Folded sedimentary and metamorphic | Varied | Basalt, andesite |
As an analytical point, the classification is a guide, and many ranges are of mixed origin; the Himalayas are folded and thrust, but also carry faulted blocks and uplifted plateaus, and the Andes combine folding with an active volcanic arc, so examination answers should name the dominant process and give an example.
Why Is This Topic Important?
- Classification Standard Prelims content
- Examples Match-the-following questions
- India Aravalli and Satpura
What Came Next?
The next topic describes the significant mountain ranges of the world. Next topic: Significant Mountain Ranges of the World.
Key People and Terms
- Fold mountain Made by compression
- Block mountain Made by faulting
- Horst Raised fault block
- Residual mountain Remnant of erosion
- Dome mountain Uplift by rising magma
- Orogeny Mountain-building episode
Exam Corner
Points to Remember
- Fold mountains are the highest and most widespread.
- Aravalli is among the oldest fold ranges.
- Vosges and Black Forest are block mountains.
- Fuji and Kilimanjaro are volcanic mountains.
- Residual mountains are left by erosion.
Do Not Confuse With
- Young and old fold mountains High and jagged versus low and rounded
- Block and fold mountains Faulting versus folding
- Residual and volcanic mountains Eroded remnant versus built-up cone
Memory Hook
Fold by squeeze, block by break, volcano by blast, residual by wear.
Mains Angle
Questions ask for types with examples. These points add depth.
- Process Compression, tension, eruption, erosion
- Age Young ranges are high; old ranges low
- Hazard Young ranges are seismic
A Question You May Face
An original practice question, not a past paper question.
“Classify mountains on the basis of their formation and give one example of each from India and the world.”
How to Answer
- Classify Fold, block, volcanic, residual.
- Process Cause of each.
- Examples India and the world.
- Age Young and old.
GS Relevance
Frequently Asked Questions
What are the main types of mountains?
Mountains are classified by formation into fold mountains, made by compression of rock layers; block mountains, made by faulting; volcanic mountains, built by lava and ash; and residual mountains, which are remnants left by erosion. Dome mountains are a less common type.
What are fold mountains?
Fold mountains are formed when compressive forces, usually at convergent plate boundaries, bend layers of rock into folds. They are the highest and most widespread type, and include the Himalayas, Alps, Andes and Rockies as young ranges, and the Aravallis and Appalachians as old ones.
What are block mountains?
Block mountains, or fault-block mountains, form when blocks of the crust are raised or lowered along faults under tension. The raised block is a horst and the sunken block a graben. The Vosges, Black Forest and Sierra Nevada are examples.
Which are the oldest fold mountains of India?
The Aravalli range of Rajasthan, Haryana and Gujarat is among the oldest fold mountains in the world, formed in the Precambrian period. It has been worn down by erosion to low, rounded hills, and Guru Shikhar at Mount Abu is its highest peak.
What are residual mountains?
Residual mountains are remnants of higher land left standing after surrounding rock was worn away over a very long time. In India the Vindhya, Satpura, Nilgiri, Parasnath and Girnar hills are examples of residual or relict mountains.
PYQ Practice — Statement Analysis
1 The Himalayas are young fold mountains.
They formed in the Alpine orogeny.
2 The Vosges and the Black Forest are fold mountains.
They are block mountains.
3 The Aravalli range is among the oldest fold mountains of the world.
It is of Precambrian age.
4 Mount Kilimanjaro is a fold mountain.
It is a volcanic mountain.
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