The Himalayan Mountain Range

1.1 What collision built the Himalaya, and when?

The Himalaya formed when the Indian Plate collided with the Eurasian Plate, roughly 50 million years ago. That collision hasn’t stopped — it’s still pushing today, which is why the range keeps rising.

1.2 Why is it called a fold-mountain range?

The collision thrust land upward, folding it into mountains, the way a rug bunches up when pushed from one end. That makes the Himalaya a classic fold-mountain range, built by pressure, not by volcanic eruptions.

2.1 What are the three belts, and how do they differ?

The range splits into three parallel belts, running north to south:

• Himadri (Greater Himalaya). The northernmost belt, holding the highest peaks — Mount Everest and Kanchenjunga among them — permanently snow-covered. About 25 km wide, averaging 6,100 metres, built from ancient granite and gneiss.
• Himachal (Lesser Himalaya). The middle belt, much wider at 60 to 80 km across, but lower, averaging 3,500 to 4,500 metres. Its rock is a mix of schist, limestone, and quartzite, squeezed and folded by the same collision that built Himadri. It holds well-known valleys like Kullu and Kangra.
• Shiwalik (Outer Himalaya). The southernmost and youngest belt, sitting lowest at roughly 900 to 1,200 metres.

2.2 Why is the Shiwalik belt different from the other two?

Unlike Himadri and Himachal, Shiwalik isn’t made of ancient rock at all. It’s built from sand, gravel, and clay that rivers washed down off the rising Himalaya itself — quite literally made from its own older siblings, worn down and redeposited.

3.1 What is a dun, and how does it form?

A dun is a long valley sitting between the Shiwalik and Himachal belts. It forms as a Lesser Himalayan river cuts across the rising Shiwaliks — first pooling into a lake behind the new ridge, then draining once the river finally cuts through.

3.2 How do rivers like the Indus cut straight through the mountains?

Here’s the puzzle: the Indus, Sutlej, and Brahmaputra all begin on the Tibetan side of the Himalaya, then somehow cross straight through it to reach the plains. The answer is that these rivers are older than the mountains themselves. As the land slowly rose beneath them, each river cut downward just as fast as the rock rose, sawing a gorge through the range instead of being pushed around it.

Picture a saw held still against a plank someone keeps pushing upward — the saw doesn’t move, but the cut still gets deeper, exactly as fast as the plank rises. This is called antecedent drainage, and it’s why the Indus gorge near Nanga Parbat and the Brahmaputra’s Dihang gorge rank among the deepest gorges on Earth.

3.3 Which mountain passes come up most in exams?

Geographers also divide the Himalaya into five regional stretches running east to west — Punjab, Kumaon, Nepal, Assam, and the Eastern Hills (Purvanchal) — cutting across the same three belts, which run more north to south. A handful of passes matter most for exams:

• Zoji La links Srinagar to Leh, the main road gateway between Kashmir and Ladakh.
• Nathu La, on the Sikkim-Tibet border, sits at about 4,310 metres and once carried Silk Route trade between India and China.
• Rohtang Pass links Kullu to Lahaul-Spiti.
• Khardung La, near Leh, climbs past 5,300 metres, connecting Leh to the Nubra Valley.

4.1 How fast is the Himalaya still growing?

The Indian Plate keeps pushing north into the Eurasian Plate, at roughly 5 centimetres a year. That ongoing push still lifts the Himalaya by a few millimetres each year, and it hasn’t stopped since the collision began. Convergence isn’t uniform along the arc either — about 13 millimetres a year in Kashmir, rising to 18 to 20 millimetres a year in the central Himalaya. Because the collision never stopped, the entire Himalayan belt remains seismically active today, not just historically.

4.2 Why did Everest’s official height change in 2020?

For decades, Nepal and China used different official heights for Everest. In December 2020, both countries jointly announced a single agreed figure: 8,848.86 metres, based on fresh GPS and trigonometric surveys. The previous widely used figure, 8,848 metres, came from an Indian survey all the way back in 1954. Six decades of slow tectonic uplift, plus better measurement technology, meant a fresh number was overdue. Because the Indian Plate keeps pushing north, Everest’s true height keeps changing by tiny amounts — the 2020 figure is the current best estimate, not a permanent one.

5.1 What are the region’s most significant earthquakes?

The Himalayan collision doesn’t just raise mountains quietly. It periodically releases huge stored energy in devastating earthquakes:

• 1934, Bihar-Nepal. Magnitude 8.2, killed around 10,500 people across Nepal and Bihar — one of the deadliest quakes in the region’s recorded history.
• 2005, Kashmir. Magnitude 7.6, killed roughly 87,000 people across Jammu and Kashmir, including Pakistan-occupied Kashmir (PoK).
• 2015, Gorkha (Nepal). Magnitude 7.8, centred near Barpak in Gorkha district, killed about 9,000 people and badly damaged Kathmandu’s historic core.

5.2 What glaciers feed India’s biggest rivers?

Siachen, at about 76 km long, is the longest glacier in the Karakoram, and the second-longest glacier anywhere outside the polar regions. Gangotri, about 32 km long, feeds the Bhagirathi river at a spot called Gaumukh, “cow’s mouth” — the Bhagirathi is one of the two headstreams that become the Ganga. Summer meltwater from glaciers like these feeds the Ganga, Indus, Brahmaputra, and their tributaries; millions of people downstream depend on ice that formed here, often without knowing it.

5.3 How rare is the snow leopard, and how many are there?

The Himalaya’s top predator hunts bharal and ibex above the tree line, often past 5,000 metres. Its grey-and-black coat blends so well into rock and snow that even experienced trackers rarely see one directly, hence its nickname, “ghost of the mountains.” India’s first-ever scientific count, released 30 January 2024, put the national snow leopard population at 718. Ladakh alone held 477 of them, the largest share by far. The same high, cold zone also supports yaks, bearded vultures, and golden eagles — a food web built entirely around surviving thin air and brutal cold.

6.1 What is the Char Dham Yatra?

Four sacred Hindu sites sit high in the Garhwal Himalaya of Uttarakhand: Yamunotri, Gangotri, Kedarnath, and Badrinath. Pilgrims traditionally visit them in that order, following the rivers from their glacial source down toward the plains. Yamunotri and Gangotri mark the glacial sources of the Yamuna and the Ganga. Kedarnath is one of the twelve Jyotirlingas of Shiva; Badrinath is a major seat of Vishnu worship. The full circuit covers over 1,600 km starting from Haridwar, and takes most pilgrims 10 to 11 days to complete.

6.2 How do terrace farming and hydropower fit in?

On slopes too steep for flat fields, hill farmers cut land into stepped terraces to grow rice, millet, and potatoes. Each terrace slows water runoff, letting farmers cultivate ground that would otherwise simply wash away. The same steep gradients and heavy glacial-and-monsoon river flow make the Himalayan states some of India’s biggest sources of untapped hydroelectric power, though dam-building here is also linked to landslide and flood risk.

7.1 What happened to India’s seismic zonation map in 2025-26?

In November 2025, the Bureau of Indian Standards issued a new earthquake design code, IS 1893:2025. It added a brand-new Zone VI, placing the entire Himalayan arc, from Arunachal Pradesh to Kashmir, in this highest-risk category for the first time. Builders and state governments raised the alarm almost immediately.

The Ministry of Housing and Urban Affairs flagged serious problems in February 2026. Zone VI construction costs could rise by 10 to 15 percent for buildings, and by up to 50 percent for infrastructure projects. The ministry also said BIS had not consulted stakeholders properly before finalising the code.

BIS withdrew IS 1893:2025 through a gazette notification on 3 March 2026, just over three months after introducing it. The older code, IS 1893:2016, is back in force, and Zone V, not the short-lived Zone VI, is now India’s official highest-risk category again. It still covers the Himalayan belt and Northeast India, so the region’s real earthquake danger has not changed, only its official rulebook has.