Maarg Manthan · Topic 3.27

Landforms of the World: Fold Mountains, Block Mountains, Volcanic Mountains

Geography › Geomorphic Processes and Landform Evolution · Topic 3.27

Mountains are landforms that rise high above the surrounding land, usually over 600 metres, with steep slopes and limited summit area. Fold mountains, such as the Himalaya, Alps, Rockies and Andes, are formed by the crumpling of rock layers under compression at plate collisions. Block mountains are formed when blocks of crust are raised or left standing between faults. Volcanic mountains are built by lava and ash, as with Mount Fuji and Kilimanjaro. Others are residual mountains left by erosion and dome mountains formed by uplift.

6 min read · UPSC Prelims · Geography · Geomorphic Processes and Landform Evolution

At a Glance

Fold mountains Himalaya, Alps, Rockies, Andes
Block mountains Vosges, Black Forest, Sierra Nevada
Volcanic mountains Fuji, Kilimanjaro, Mauna Loa
Residual mountains Aravalli, Nilgiri
Oldest fold range in India Aravalli
Exam link UPSC Prelims, Geography: Geomorphic Processes and Landform Evolution

Where Does It Fit?

This topic begins the last part of the macro, which describes the major landforms of the world, after the processes that shape them. It draws on plate tectonics and faulting, and it pairs with the next topic on plateaus. Previous topic: Coastal Depositional Landforms: Beaches, Dunes, Bars, Barriers, Spits. Next topic: Plateaus: Formation, Types (Dissected, Volcanic), Economic Significance, Major Plateaus 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: Major and Minor Lithospheric Plates.

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 Processes: Diastrophism, Orogenic and Epeirogenic Processes. 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 Types of Lava: Andesitic (Acidic) and Basaltic (Basic) Lava.

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.

Which Are the Major Mountain Systems of the World?

Range	Continent	Type and age	Notable fact
Himalaya	Asia	Fold; young (Tertiary)	Highest range; Mount Everest 8,849 m (2020 survey figure); still rising
Alps	Europe	Fold; young	Mont Blanc is the highest peak
Rockies	North America	Fold; relatively young	Part of the American Cordillera
Andes	South America	Fold with volcanoes; young	Longest continental range, about 7,000 km
Atlas	Africa	Fold	Part of the Alpine system
Urals	Russia	Old fold, worn down	Boundary between Europe and Asia
Appalachians	North America	Old fold	Eroded to low ridges
Aravalli	India	Very old fold; residual	Among the oldest fold ranges in the world

The mountain systems are described further in the macro on the physical geography of the world, and the formation of the Himalaya by plate collision in Plate Boundaries: Divergent, Convergent, Transform. As an analytical point, the age of a range tells its form: young ranges are high, sharp and seismically active, while old ranges are low, rounded and quiet.

Why Is This Topic Important?

Classification Standard Prelims content
Examples Match-the-following questions
India Aravalli and Satpura

What Came Next?

The next topic covers plateaus: how they form, their types, their economic value and the major plateaus of the world. Next topic: Plateaus: Formation, Types (Dissected, Volcanic), Economic Significance, Major Plateaus 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

Prelims: types of mountains with examples, oldest and youngest ranges. GS Paper 1: world's physical geography, mountains.

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.

True

They formed in the Alpine orogeny.

2 The Vosges and the Black Forest are fold mountains.

False

They are block mountains.

3 The Aravalli range is among the oldest fold mountains of the world.