Mountains — Types, Formation, and Distribution

2.1 Fold Mountains

Fold mountains are formed by the convergent movement of tectonic plates compressing and folding sedimentary rock strata into ridges and troughs (anticlines and synclines). They are the most common and highest mountain type, always geologically young (Tertiary/Cenozoic) if still high.

Global Distribution:

Mountain Range	Location	Length	Highest Peak	Age of Formation
Himalayas	South Asia (India-Nepal-China)	~2,400 km	Mt. Everest 8,848.86 m	~50 Ma (Eocene)
Karakoram	Pakistan-China-India border	~500 km	K2 8,611 m	~60–30 Ma
Hindu Kush	Afghanistan-Pakistan	~800 km	Tirich Mir 7,708 m	~35–5 Ma
Andes	Western South America	~7,000 km	Aconcagua 6,961 m	~25 Ma
Rocky Mountains	Western North America	~4,800 km	Mt. Elbert 4,399 m	Laramide Orogeny 85–55 Ma
Alps	Central Europe	~1,200 km	Mont Blanc 4,808 m	~35 Ma
Pyrenees	France-Spain border	~430 km	Aneto 3,404 m	~40 Ma
Caucasus	Russia-Georgia-Armenia	~1,200 km	Mt. Elbrus 5,642 m	~30 Ma
Atlas Mountains	North Africa	~2,500 km	Toubkal 4,167 m	~20 Ma

Ancient Fold Mountains (old, worn down — no longer active):

• Aravallis (India) — ~1,500 Ma (Precambrian); Guru Shikhar 1,722 m
• Appalachians (USA-Canada) — ~300 Ma (Carboniferous); Mt. Mitchell 2,037 m
• Ural Mountains (Russia) — ~250–300 Ma; Mt. Narodnaya 1,895 m

2.2 Rocky Mountains — Detailed Study (PYQ 2021, 5 marks)

The Rocky Mountains are the major mountain system of western North America, forming the backbone of the continent.

Location and Extent

• Extend 4,800 km (approximately) from northern British Columbia (Canada) to New Mexico (USA)
• Part of the American Cordillera — the great mountain chain running along both Americas' Pacific coast

Formation

• Formed during the Laramide Orogeny (85–55 Ma) when the shallow-angled subduction of the Farallon Plate under the North American Plate pushed up Precambrian basement rocks and overlying sedimentary sequences
• Unlike pure fold mountains, the Rockies involve a mix of fold, fault, and uplift mechanisms

Physical Features

• Highest peak: Mount Elbert, Colorado — 4,399 m (Southern Rockies/Sawatch Range)
• Continental Divide (Great Divide): Separates westward drainage (Pacific Ocean: Columbia, Fraser, Colorado rivers) from eastward drainage (Atlantic/Gulf of Mexico: Missouri, Arkansas, Platte rivers)
• Major sections: Canadian Rockies (Banff, Jasper) → Northern Rockies (Idaho, Montana) → Middle Rockies (Wyoming — Yellowstone) → Southern Rockies (Colorado — highest elevations)
• Yellowstone National Park sits atop a volcanic hotspot — the Yellowstone Caldera (72 km × 55 km) is one of the world's largest supervolcanoes
• Glacier National Park (Montana) — glacially sculpted landscapes; glaciers rapidly retreating due to climate change

Economic Significance

• Mineral wealth: Gold (Colorado Gold Rush, 1859), silver, copper, molybdenum (largest deposits at Climax, Colorado)
• Energy: Natural gas, oil shale (Green River Formation — world's largest oil shale deposit)
• Tourism: Skiing (Aspen, Vail, Banff), national parks, wildlife (grizzly bears, elk, wolves)
• Water: Major source of irrigation water for the American West (Colorado River Basin compact)

2.3 Block Mountains / Fault-Block Mountains

Formation: When tensional forces pull the crust apart along parallel faults, the middle section may drop (creating a Graben or Rift Valley) while the flanking blocks rise as Horsts (block mountains). Alternatively, compression can force a central block upward.

Examples:

Block Mountain	Location	Key Facts
Vosges	Eastern France	Flanks western side of Rhine Graben; max height 1,423 m (Grand Ballon)
Black Forest (Schwarzwald)	SW Germany	Flanks eastern side of Rhine Graben; max 1,493 m (Feldberg)
Sierra Nevada	California, USA	Tilted fault block; Mt. Whitney 4,421 m — highest peak in contiguous USA
Harz Mountains	Germany	Ancient horst
Vindhyas	Central India	Fault-block type; separates Indo-Gangetic Plain from Deccan
Satpura	Central India	Horst between Narmada and Tapti rift valleys (Graben)

Rhine Graben System: Classic example — the Rhine River flows through the sunken valley (Graben) between Vosges (France) and Black Forest (Germany). This rift system is geologically related to the East African Rift.

2.4 Volcanic Mountains

Formation: Accumulation of volcanic material (lava, pyroclastic deposits, ash) around a vent.

Type	Shape	Lava	Explosivity	Examples
Shield Volcano	Broad, gentle slopes (2°–10°)	Basaltic (low viscosity, flows easily)	Low	Mauna Loa/Mauna Kea (Hawaii), Etna (Italy)
Composite/Strato Volcano	Steep-sided, cone-shaped (30°–40°)	Andesitic/Rhyolitic (viscous)	High, explosive	Mt. Fuji (3,776 m), Krakatoa, Pinatubo, Vesuvius
Cinder Cone	Small, steep, symmetrical cone	Basaltic fragments/cinders	Moderate	Paricutín (Mexico), Sunset Crater (Arizona)
Lava Dome	Rounded, steep dome	Very viscous rhyolitic	Extreme	Mt. St. Helens dome (after 1980 eruption)

Highest Volcanic Peaks:

• Mauna Kea (Hawaii): 4,205 m above sea level; 10,210 m from ocean floor — Earth's tallest mountain measured from base
• Ojos del Salado (Andes, Chile-Argentina border): 6,893 m — world's highest active volcano
• Mt. Kilimanjaro (Tanzania): 5,895 m — Africa's highest; dormant stratovolcano; three volcanic cones

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